LM2594, LM2594HV
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LM2594/LM2594HV SIMPLE SWITCHER
®
Power Converter 150 kHz 0.5A Step-Down
Voltage Regulator
Check for Samples: LM2594,LM2594HV
1FEATURES DESCRIPTION
The LM2594/LM2594HV series of regulators are
2345• 3.3V, 5V, 12V, and Adjustable Output Versions monolithic integrated circuits that provide all the
• Adjustable Version Output Voltage Range, active functions for a step-down (buck) switching
1.2V to 37V (57V for the HV Version)±4% Max regulator, capable of driving a 0.5A load with
Over Line and Load Conditions excellent line and load regulation. These devices are
available in fixed output voltages of 3.3V, 5V, 12V,
• Available in 8-pin Surface Mount SOIC and and an adjustable output version, and are packaged
PDIP-8 Package in a 8-lead PDIP and a 8-lead surface mount SOIC
• Ensured 0.5A Output Current package.
• Input Voltage Range up to 60V Requiring a minimum number of external
• Requires only 4 External Components components, these regulators are simple to use and
• 150 kHz Fixed Frequency Internal Oscillator feature internal frequency compensation†, a fixed-
frequency oscillator, and improved line and load
• TTL Shutdown Capability regulation specifications.
• Low Power Standby Mode, IQtypically 85 μAThe LM2594/LM2594HV series operates at a
• High Efficiency switching frequency of 150 kHz thus allowing smaller
• Uses Readily Available Standard Inductors sized filter components than what would be needed
• Thermal Shutdown and Current Limit with lower frequency switching regulators. Because of
Protection its high efficiency, the copper traces on the printed
circuit board are normally the only heat sinking
needed.
APPLICATIONS A standard series of inductors (both through hole and
• Simple High-efficiency Step-down (Buck) surface mount types) are available from several
Regulator different manufacturers optimized for use with the
• Efficient Pre-regulator for Linear Regulators LM2594/LM2594HV series. This feature greatly
• On-card Switching Regulators simplifies the design of switch-mode power supplies.
• Positive to Negative Convertor Other features include an ensured ±4% tolerance on
output voltage under all conditions of input voltage
and output load conditions, and ±15% on the
oscillator frequency. External shutdown is included,
featuring typically 85 μA standby current. Self
protection features include a two stage frequency
reducing current limit for the output switch and an
over temperature shutdown for complete protection
under fault conditions.
The LM2594HV is for applications requiring an input
voltage up to 60V.
1Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2Switchers Made Simple is a trademark of Texas Instruments.
3SIMPLE SWITCHER is a registered trademark of Texas Instruments.
4Switchers Made Simple is a registered trademark of dcl_owner.
5All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 1999–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
LM2594, LM2594HV
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Typical Application
(Fixed Output Voltage Versions)
Connection Diagrams and Order Information
Figure 1. 8-Pin - Top View Figure 2. 8-Pin - Top View
See Package Number P0008E See Package Number D0008A
*No internal connection, but should be soldered to pc board for best heat transfer.
‡Patent Number 5,382,918.
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings(1)(2)
Maximum Supply Voltage
LM2594 45V
LM2594HV 60V
ON /OFF Pin Input Voltage −0.3 ≤V≤+25V
Feedback Pin Voltage −0.3 ≤V≤+25V
Output Voltage to Ground (Steady State) −1V
Power Dissipation Internally limited
Storage Temperature Range −65°C to +150°C
ESD Susceptibility Human Body Model(3) 2 kV
Lead Temperature
D8 Package Vapor Phase (60 sec.) +215°C
Infrared (15 sec.) +220°C
P Package (Soldering, 10 sec.) +260°C
Maximum Junction Temperature +150°C
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but do not ensure specific performance limits. For ensured specifications and test
conditions, see the Electrical Characteristics.
(2) If Military/Aerospace specified devices are required, please contact the TI Sales Office/ Distributors for availability and specifications.
(3) The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Operating Conditions
Temperature Range −40°C ≤TJ+125°C
Supply Voltage
LM2594 4.5V to 40V
LM2594HV 4.5V to 60V
LM2594/LM2594HV-3.3 Electrical Characteristics
Specifications with standard type face are for TJ= 25°C, and those with boldface type apply over full Operating
Temperature Range.VINmax= 40V for the LM2594 and 60V for the LM2594HV.
Symbol Parameter Conditions LM2594/LM2594HV-3.3 Units
(Limits)
Typ(1) Limit(2)
SYSTEM PARAMETERS(3) Test Circuit Figure 20
VOUT Output Voltage 4.75V ≤VIN ≤VINmax, 0.1A ≤ILOAD ≤0.5A 3.3 V
3.432/3.465 V(min)
3.168/3.135 V(max)
ηEfficiency VIN = 12V, ILOAD = 0.5A 80 %
(1) Typical numbers are at 25°C and represent the most likely norm.
(2) All limits ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits
are 100% production tested. All limits at temperature extremes are specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator system performance. When the LM2594/LM2594HV is used as shown in the Figure 20 test circuit, system
performance will be as shown in system parameters section of Electrical Characteristics.
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LM2594/LM2594HV-5.0 Electrical Characteristics
Specifications with standard type face are for TJ= 25°C, and those with boldface type apply over full Operating
Temperature Range
Symbol Parameter Conditions LM2594/LM2594HV-5.0 Units
(Limits)
Typ(1) Limit(2)
SYSTEM PARAMETERS(3) Test Circuit Figure 20
VOUT Output Voltage 7V ≤VIN ≤VINmax, 0.1A ≤ILOAD ≤0.5A 5.0 V
4.800/4.750 V(min)
5.200/5.250 V(max)
ηEfficiency VIN = 12V, ILOAD = 0.5A 82 %
(1) Typical numbers are at 25°C and represent the most likely norm.
(2) All limits ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits
are 100% production tested. All limits at temperature extremes are specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator system performance. When the LM2594/LM2594HV is used as shown in the Figure 20 test circuit, system
performance will be as shown in system parameters section of Electrical Characteristics.
LM2594/LM2594HV-12 Electrical Characteristics
Specifications with standard type face are for TJ= 25°C, and those with boldface type apply over full Operating
Temperature Range
Symbol Parameter Conditions LM2594/LM2594HV-12 Units
(Limits)
Typ(1) Limit(2)
SYSTEM PARAMETERS(3) Test Circuit Figure 20
VOUT Output Voltage 15V ≤VIN ≤VINmax, 0.1A ≤ILOAD ≤0.5A 12.0 V
11.52/11.40 V(min)
12.48/12.60 V(max)
ηEfficiency VIN = 25V, ILOAD = 0.5A 88 %
(1) Typical numbers are at 25°C and represent the most likely norm.
(2) All limits ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits
are 100% production tested. All limits at temperature extremes are specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator system performance. When the LM2594/LM2594HV is used as shown in the Figure 20 test circuit, system
performance will be as shown in system parameters section of Electrical Characteristics.
LM2594/LM2594HV-ADJ Electrical Characteristics
Specifications with standard type face are for TJ= 25°C, and those with boldface type apply over full Operating
Temperature Range
Symbol Parameter Conditions LM2594/LM2594HV-ADJ Units
(Limits)
Typ(1) Limit(2)
SYSTEM PARAMETERS(3) Test Circuit Figure 20
VFB Feedback Voltage 4.5V ≤VIN ≤VINmax, 0.1A ≤ILOAD ≤0.5A 1.230 V
1.193/1.180
VOUT programmed for 3V. Circuit of Figure 20 V(min)
1.267/1.280 V(max)
ηEfficiency VIN = 12V, ILOAD = 0.5A 80 %
(1) Typical numbers are at 25°C and represent the most likely norm.
(2) All limits ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits
are 100% production tested. All limits at temperature extremes are specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator system performance. When the LM2594/LM2594HV is used as shown in the Figure 20 test circuit, system
performance will be as shown in system parameters section of Electrical Characteristics.
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All Output Voltage Versions Electrical Characteristics
Specifications with standard type face are for TJ= 25°C, and those with boldface type apply over full Operating
Temperature Range . Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the
12V version. ILOAD = 100 mA
Symbol Parameter Conditions LM2594/LM2594HV-XX Units
(Limits)
Typ(1) Limit(2)
DEVICE PARAMETERS
IbFeedback Bias Current Adjustable Version Only, VFB = 1.3V 10 50/100 nA
fOOscillator Frequency See(3) 150 kHz
127/110 kHz(min)
173/173 kHz(max)
VSAT Saturation Voltage IOUT = 0.5A(4)(5) 0.9 V
1.1/1.2 V(max)
DC Max Duty Cycle (ON) See(5) 100 %
Min Duty Cycle (OFF) See(6) 0
ICL Current Limit Peak Current(4)(5) 0.8 A
0.65/0.58 A(min)
1.3/1.4 A(max)
ILOutput Leakage Current Output = 0V(4)(6)(7) 50 μA(max)
Output = −1V 2 mA
15 mA(max)
IQQuiescent Current See(6) 5 mA
10 mA(max)
ISTBY Standby Quiescent Current ON/OFF pin = 5V (OFF)(7) 85 μA
LM2594 200/250 μA(max)
LM2594HV 140 250/300 μA(max)
θJA Thermal Resistance P Package, Junction to Ambient(8) 95 °C/W
MDPackage, Junction to Ambient(8) 150
ON/OFF CONTROL Test Circuit Figure 20
ON /OFF Pin Logic Input 1.3 V
VIH Threshold Voltage Low (Regulator ON) 0.6 V(max)
VIL High (Regulator OFF) 2.0 V(min)
IHON /OFF Pin Input Current VLOGIC = 2.5V (Regulator OFF) 5 μA
15 μA(max)
ILVLOGIC = 0.5V (Regulator ON) 0.02 μA
5μA(max)
(1) Typical numbers are at 25°C and represent the most likely norm.
(2) All limits ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits
are 100% production tested. All limits at temperature extremes are specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
(3) The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is determined by the
severity of current overload.
(4) No diode, inductor or capacitor connected to output pin.
(5) Feedback pin removed from output and connected to 0V to force the output transistor switch ON.
(6) Feedback pin removed from output and connected to 12V for the 3.3V, 5V, and the ADJ. version, and 15V for the 12V version, to force
the output transistor switch OFF.
(7) VIN = 40V for the LM2594 and 60V for the LM2594HV.
(8) Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional
copper area will lower thermal resistance further. See application hints in this data sheet and the thermal model in Switchers Made
Simple®software.
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Typical Performance Characteristics
Normalized
Output Voltage Line Regulation
Figure 3. Figure 4.
Switch Saturation
Efficiency Voltage
Figure 5. Figure 6.
Switch Current Limit Dropout Voltage
Figure 7. Figure 8.
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Typical Performance Characteristics (continued)
Standby
Quiescent Current Quiescent Current
Figure 9. Figure 10.
Minimum Operating ON /OFF Threshold
Supply Voltage Voltage
Figure 11. Figure 12.
ON /OFF Pin
Current (Sinking) Switching Frequency
Figure 13. Figure 14.
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Typical Performance Characteristics
Continuous Mode Switching Waveforms Discontinuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 400 mA VIN = 20V, VOUT = 5V, ILOAD = 200 mA
L = 100 μH, COUT = 120 μF, COUT ESR = 140 mΩL = 33 μH, COUT = 220 μF, COUT ESR = 60 mΩ
A: Output Pin Voltage, 10V/div. A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.2A/div. B: Inductor Current 0.2A/div.
C: Output Ripple Voltage, 20 mV/div. C: Output Ripple Voltage, 20 mV/div.
Figure 16. Horizontal Time Base: 2 μs/div. Figure 17. Horizontal Time Base: 2 μs/div.
Load Transient Response for Continuous Mode Load Transient Response for Discontinuous Mode
VIN = 20V, VOUT = 5V, ILOAD = 200 mA to 500 mA VIN = 20V, VOUT = 5V, ILOAD = 100 mA to 200 mA
L = 100 μH, COUT = 120 μF, COUT ESR = 140 mΩL = 33 μH, COUT = 220 μF, COUT ESR = 60 mΩ
A: Output Voltage, 50 mV/div. (AC)
B: 100 mA to 200 mA Load Pulse
A: Output Voltage, 50 mV/div. (AC)
B: 200 mA to 500 mA Load Pulse
Figure 18. Horizontal Time Base: 50 μs/div. Figure 19. Horizontal Time Base: 200 μs/div.
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TYPICAL CIRCUIT AND LAYOUT GUIDELINES
Fixed Output Voltage Versions
CIN — 68 μF, 35V, Aluminum Electrolytic Nichicon “PL Series”
COUT — 120 μF, 25V Aluminum Electrolytic, Nichicon “PL Series”
D1 — 1A, 40V Schottky Rectifier, 1N5819
L1 — 100 μH, L20
Select components with higher voltage ratings for designs using the LM2594HV with an input voltage between
40V and 60V.
Adjustable Output Voltage Versions
CIN — 68 μF, 35V, Aluminum Electrolytic Nichicon “PL Series”
COUT — 120 μF, 25V Aluminum Electrolytic, Nichicon “PL Series”
D1 — 1A, 40V Schottky Rectifier, 1N5819
L1 — 100 μH, L20
R1— 1 kΩ, 1%
CFF — See Application Information Section
Figure 20. Typical Circuits and Layout Guides
As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring
inductance can generate voltage transients which can cause problems. For minimal inductance and ground
loops, the wires indicated by heavy lines should be wide printed circuit traces and should be kept as short
as possible. For best results, external components should be located as close to the switcher lC as possible
using ground plane construction or single point grounding.
If open core inductors are used, special care must be taken as to the location and positioning of this type of
inductor. Allowing the inductor flux to intersect sensitive feedback, lC groundpath and COUT wiring can cause
problems.
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When using the adjustable version, special care must be taken as to the location of the feedback resistors and
the associated wiring. Physically locate both resistors near the IC, and route the wiring away from the inductor,
especially an open core type of inductor. (See Application Information section for more information.)
Table 1. LM2594/LM2594HV Series Buck Regulator Design Procedure (Fixed Output)
PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version)
Given: Given:
VOUT = Regulated Output Voltage (3.3V, 5V or 12V) VOUT = 5V
VIN(max) = Maximum DC Input Voltage VIN(max) = 12V
ILOAD(max) = Maximum Load Current ILOAD(max) = 0.4A
1. Inductor Selection (L1) 1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from Figure 21 A. Use the inductor selection guide for the 5V version shown in
Figure 22 or Figure 23. (Output voltages of 3.3V, 5V, or 12V Figure 22.
respectively.) For all other voltages, see the design procedure for the B. From the inductor value selection guide shown in Figure 22, the
adjustable version. inductance region intersected by the 12V horizontal line and the 0.4A
B. From the inductor value selection guide, identify the inductance vertical line is 100 μH, and the inductor code is L20.
region intersected by the Maximum Input Voltage line and the C. The inductance value required is 100 μH. From Table 5, go to the
Maximum Load Current line. Each region is identified by an L20 line and choose an inductor part number from any of the four
inductance value and an inductor code (LXX). manufacturers shown. (In most instance, both through hole and
C. Select an appropriate inductor from the four manufacturer's part surface mount inductors are available.)
numbers listed in Table 5.
2. Output Capacitor Selection (COUT) 2. Output Capacitor Selection (COUT)
A. In the majority of applications, low ESR (Equivalent Series A. See OUTPUT CAPACITOR section in Application Information
Resistance) electrolytic capacitors between 82 μF and 220 μF and section.
low ESR solid tantalum capacitors between 15 μF and 100 μFB. From the quick design component selection table shown in
provide the best results. This capacitor should be located close to Figure 24, locate the 5V output voltage section. In the load current
the IC using short capacitor leads and short copper traces. Do not column, choose the load current line that is closest to the current
use capacitors larger than 220 μF. needed in your application, for this example, use the 0.5A line. In the
For additional information, see OUTPUT CAPACITOR section in maximum input voltage column, select the line that covers the input
Application Information section. voltage needed in your application, in this example, use the 15V line.
Continuing on this line are recommended inductors and capacitors
B. To simplify the capacitor selection procedure, refer to the quick that will provide the best overall performance.
design component selection table shown in Figure 24. This table
contains different input voltages, output voltages, and load currents, The capacitor list contains both through hole electrolytic and surface
and lists various inductors and output capacitors that will provide the mount tantalum capacitors from four different capacitor
best design solutions. manufacturers. It is recommended that both the manufacturers and
the manufacturer's series that are listed in the table be used.
C. The capacitor voltage rating for electrolytic capacitors should be
at least 1.5 times greater than the output voltage, and often much In this example aluminum electrolytic capacitors from several
higher voltage ratings are needed to satisfy the low ESR different manufacturers are available with the range of ESR numbers
requirements for low output ripple voltage. needed.
D. For computer aided design software, see Switchers Made 120 μF 25V Panasonic HFQ Series
Simple™ version 4.1 or later. 120 μF 25V Nichicon PL Series
C. For a 5V output, a capacitor voltage rating at least 7.5V or more
is needed. But, in this example, even a low ESR, switching grade,
120 μF 10V aluminum electrolytic capacitor would exhibit
approximately 400 mΩof ESR (see the curve in Figure 26 for the
ESR vs voltage rating). This amount of ESR would result in relatively
high output ripple voltage. To reduce the ripple to 1% of the output
voltage, or less, a capacitor with a higher voltage rating (lower ESR)
should be selected. A 16V or 25V capacitor will reduce the ripple
voltage by approximately half.
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Table 1. LM2594/LM2594HV Series Buck Regulator Design Procedure (Fixed Output) (continued)
PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version)
3. Catch Diode Selection (D1) 3. Catch Diode Selection (D1)
A. The catch diode current rating must be at least 1.3 times greater A. Refer to the table shown in Table 8. In this example, a 1A, 20V,
than the maximum load current. Also, if the power supply design 1N5817 Schottky diode will provide the best performance, and will
must withstand a continuous output short, the diode should have a not be overstressed even for a shorted output.
current rating equal to the maximum current limit of the LM2594. The
most stressful condition for this diode is an overload or shorted
output condition.
B. The reverse voltage rating of the diode should be at least 1.25
times the maximum input voltage.
C. This diode must be fast (short reverse recovery time) and must be
located close to the LM2594 using short leads and short printed
circuit traces. Because of their fast switching speed and low forward
voltage drop, Schottky diodes provide the best performance and
efficiency, and should be the first choice, especially in low output
voltage applications. Ultra-fast recovery, or High-Efficiency rectifiers
also provide good results. Ultra-fast recovery diodes typically have
reverse recovery times of 50 ns or less. Rectifiers such as the
1N4001 series are much too slow and should not be used.
4. Input Capacitor (CIN) 4. Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is needed The important parameters for the Input capacitor are the input
between the input pin and ground to prevent large voltage transients voltage rating and the RMS current rating. With a nominal input
from appearing at the input. In addition, the RMS current rating of voltage of 12V, an aluminum electrolytic capacitor with a voltage
the input capacitor should be selected to be at least ½ the DC load rating greater than 18V (1.5 × VIN) would be needed. The next
current. The capacitor manufacturers data sheet must be checked to higher capacitor voltage rating is 25V.
assure that this current rating is not exceeded. The curve shown in The RMS current rating requirement for the input capacitor in a buck
Figure 25 shows typical RMS current ratings for several different regulator is approximately ½ the DC load current. In this example,
aluminum electrolytic capacitor values. with a 400 mA load, a capacitor with a RMS current rating of at least
This capacitor should be located close to the IC using short leads 200 mA is needed. The curves shown in Figure 25 can be used to
and the voltage rating should be approximately 1.5 times the select an appropriate input capacitor. From the curves, locate the
maximum input voltage. 25V line and note which capacitor values have RMS current ratings
greater than 200 mA. Either a 47 μF or 68 μF, 25V capacitor could
If solid tantalum input capacitors are used, it is recommended that be used.
they be surge current tested by the manufacturer. For a through hole design, a 68 μF/25V electrolytic capacitor
Use caution when using ceramic capacitors for input bypassing, (Panasonic HFQ series or Nichicon PL series or equivalent) would
because it may cause severe ringing at the VIN pin. be adequate. Other types or other manufacturers capacitors can be
For additional information, see EXTERNAL COMPONENTS used provided the RMS ripple current ratings are adequate.
section on input capacitors in Application Information section. For surface mount designs, solid tantalum capacitors are
recommended. The TPS series available from AVX, and the 593D
series from Sprague are both surge current tested.
Table 2. LM2594/LM2594HV Fixed Voltage Quick Design Component Selection Table
Conditions Inductor Output Capacitor
Through Hole Surface Mount
Output Load Max Input Inductance Inductor Panasonic Nichicon AVX TPS Sprague
Voltage Current Voltage (μH) (#) HFQ Series PL Series Series 595D Series
(V) (A) (V) (μF/V) (μF/V) (μF/V) (μF/V)
3.3 0.5 5 33 L14 220/16 220/16 100/16 100/6.3
7 47 L13 120/25 120/25 100/16 100/6.3
10 68 L21 120/25 120/25 100/16 100/6.3
40 100 L20 120/35 120/35 100/16 100/6.3
6 68 L4 120/25 120/25 100/16 100/6.3
0.2 10 150 L10 120/16 120/16 100/16 100/6.3
40 220 L9 120/16 120/16 100/16 100/6.3
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Table 2. LM2594/LM2594HV Fixed Voltage Quick Design Component Selection Table (continued)
Conditions Inductor Output Capacitor
Through Hole Surface Mount
Output Load Max Input Inductance Inductor Panasonic Nichicon AVX TPS Sprague
Voltage Current Voltage (μH) (#) HFQ Series PL Series Series 595D Series
(V) (A) (V) (μF/V) (μF/V) (μF/V) (μF/V)
50.5 8 47 L13 180/16 180/16 100/16 33/25
10 68 L21 180/16 180/16 100/16 33/25
15 100 L20 120/25 120/25 100/16 33/25
40 150 L19 120/25 120/25 100/16 33/25
9 150 L10 82/16 82/16 100/16 33/25
0.2 20 220 L9 120/16 120/16 100/16 33/25
40 330 L8 120/16 120/16 100/16 33/25
12 0.5 15 68 L21 82/25 82/25 100/16 15/25
18 150 L19 82/25 82/25 100/16 15/25
30 220 L27 82/25 82/25 100/16 15/25
40 330 L26 82/25 82/25 100/16 15/25
15 100 L11 82/25 82/25 100/16 15/25
0.2 20 220 L9 82/25 82/25 100/16 15/25
40 330 L17 82/25 82/25 100/16 15/25
Table 3. LM2594/LM2594HV Series Buck Regulator Design Procedure (Adjustable Output)
PROCEDURE (Adjustable Output Voltage Version) EXAMPLE (Adjustable Output Voltage Version)
Given: Given:
VOUT = Regulated Output Voltage VOUT = 20V
VIN(max) = Maximum Input Voltage VIN(max) = 28V
ILOAD(max) = Maximum Load Current ILOAD(max) = 0.5A
F = Switching Frequency (Fixed at a nominal 150 kHz). F = Switching Frequency (Fixed at a nominal 150 kHz).
1. Programming Output Voltage (Selecting R1and R2, as shown in 1. Programming Output Voltage (Selecting R1and R2, as shown in
Figure 20.Figure 20 )
Use the following formula to select the appropriate resistor values. Select R1to be 1 kΩ, 1%. Solve for R2.
(3)
(1)
R2= 1k (16.26 −1) = 15.26k, closest 1% value is 15.4 kΩ.
Select a value for R1between 240Ωand 1.5 kΩ. The lower resistor
values minimize noise pickup in the sensitive feedback pin. (For the R2= 15.4 kΩ.
lowest temperature coefficient and the best stability with time, use
1% metal film resistors.)
(2)
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Table 3. LM2594/LM2594HV Series Buck Regulator Design Procedure (Adjustable Output) (continued)
PROCEDURE (Adjustable Output Voltage Version) EXAMPLE (Adjustable Output Voltage Version)
2. Inductor Selection (L1) 2. Inductor Selection (L1)
A. Calculate the inductor Volt microsecond constant E • T (V • μs) , A. Calculate the inductor Volt • microsecond constant (E • T) ,
from the following formula:
(4)
where VSAT = internal switch saturation voltage = 0.9V (5)
and VD= diode forward voltage drop = 0.5V B. E • T = 35.2 (V • μs)
B. Use the E • T value from the previous formula and match it with C. ILOAD(max) = 0.5A
the E • T number on the vertical axis of the Inductor Value Selection D. From the inductor value selection guide shown in Figure 24, the
Guide shown in Figure 24.inductance region intersected by the 35 (V • μs) horizontal line and
C. on the horizontal axis, select the maximum load current. the 0.5A vertical line is 150 μH, and the inductor code is L19.
D. Identify the inductance region intersected by the E • T value and E. From Table 5, locate line L19, and select an inductor part number
the Maximum Load Current value. Each region is identified by an from the list of manufacturers part numbers.
inductance value and an inductor code (LXX).
E. Select an appropriate inductor from the four manufacturer's part
numbers listed in Table 5.
3. Output Capacitor Selection (COUT) 3. Output Capacitor SeIection (COUT)
A. In the majority of applications, low ESR electrolytic or solid A. See OUTPUT CAPACITORsection on COUT in Application
tantalum capacitors between 82 μF and 220 μF provide the best Information section.
results. This capacitor should be located close to the IC using short B. From the quick design table shown in Table 4, locate the output
capacitor leads and short copper traces. Do not use capacitors voltage column. From that column, locate the output voltage closest
larger than 220 μF. For additional information, see OUTPUT to the output voltage in your application. In this example, select the
CAPACITOR section in Application Information section. 24V line. Under the OUTPUT CAPACITORoutput capacitor, select a
B. To simplify the capacitor selection procedure, refer to the quick capacitor from the list of through hole electrolytic or surface mount
design table shown in Table 4. This table contains different output tantalum types from four different capacitor manufacturers. It is
voltages, and lists various output capacitors that will provide the best recommended that both the manufacturers and the manufacturers
design solutions. series that are listed in the table be used.
C. The capacitor voltage rating should be at least 1.5 times greater In this example, through hole aluminum electrolytic capacitors from
than the output voltage, and often much higher voltage ratings are several different manufacturers are available.
needed to satisfy the low ESR requirements needed for low output 82 μF 50V Panasonic HFQ Series
ripple voltage. 120 μF 50V Nichicon PL Series
C. For a 20V output, a capacitor rating of at least 30V or more is
needed. In this example, either a 35V or 50V capacitor would work.
A 50V rating was chosen because it has a lower ESR which
provides a lower output ripple voltage.
Other manufacturers or other types of capacitors may also be used,
provided the capacitor specifications (especially the 100 kHz ESR)
closely match the types listed in the table. Refer to the capacitor
manufacturers data sheet for this information.
4. Feedforward Capacitor (CFF)(See Figure 20 )4. Feedforward Capacitor (CFF)
For output voltages greater than approximately 10V, an additional The table shown in Table 4 contains feed forward capacitor values
capacitor is required. The compensation capacitor is typically for various output voltages. In this example, a 1 nF capacitor is
between 50 pF and 10 nF, and is wired in parallel with the output needed.
voltage setting resistor, R2. It provides additional stability for high
output voltages, low input-output voltages, and/or very low ESR
output capacitors, such as solid tantalum capacitors.
(6)
This capacitor type can be ceramic, plastic, silver mica, etc.
(Because of the unstable characteristics of ceramic capacitors made
with Z5U material, they are not recommended.)
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Table 3. LM2594/LM2594HV Series Buck Regulator Design Procedure (Adjustable Output) (continued)
PROCEDURE (Adjustable Output Voltage Version) EXAMPLE (Adjustable Output Voltage Version)
5. Catch Diode Selection (D1) 5. Catch Diode Selection (D1)
A. The catch diode current rating must be at least 1.3 times greater A. Refer to the table shown in Table 8. Schottky diodes provide the
than the maximum load current. Also, if the power supply design best performance, and in this example a 1A, 40V, 1N5819 Schottky
must withstand a continuous output short, the diode should have a diode would be a good choice. The 1A diode rating is more than
current rating equal to the maximum current limit of the LM2594. The adequate and will not be overstressed even for a shorted output.
most stressful condition for this diode is an overload or shorted
output condition.
B. The reverse voltage rating of the diode should be at least 1.25
times the maximum input voltage.
C. This diode must be fast (short reverse recovery time) and must be
located close to the LM2594 using short leads and short printed
circuit traces. Because of their fast switching speed and low forward
voltage drop, Schottky diodes provide the best performance and
efficiency, and should be the first choice, especially in low output
voltage applications. Ultra-fast recovery, or High-Efficiency rectifiers
are also a good choice, but some types with an abrupt turn-off
characteristic may cause instability or EMl problems. Ultra-fast
recovery diodes typically have reverse recovery times of 50 ns or
less. Rectifiers such as the 1N4001 series are much too slow and
should not be used.
6. Input Capacitor (CIN) 6. Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is needed The important parameters for the Input capacitor are the input
between the input pin and ground to prevent large voltage transients voltage rating and the RMS current rating. With a nominal input
from appearing at the input. In addition, the RMS current rating of voltage of 28V, an aluminum electrolytic aluminum electrolytic
the input capacitor should be selected to be at least ½ the DC load capacitor with a voltage rating greater than 42V (1.5 × VIN) would be
current. The capacitor manufacturers data sheet must be checked to needed. Since the the next higher capacitor voltage rating is 50V, a
assure that this current rating is not exceeded. The curve shown in 50V capacitor should be used. The capacitor voltage rating of (1.5 ×
Figure 25 shows typical RMS current ratings for several different VIN) is a conservative guideline, and can be modified somewhat if
aluminum electrolytic capacitor values. desired.
This capacitor should be located close to the IC using short leads The RMS current rating requirement for the input capacitor of a buck
and the voltage rating should be approximately 1.5 times the regulator is approximately ½ the DC load current. In this example,
maximum input voltage. with a 400 mA load, a capacitor with a RMS current rating of at least
200 mA is needed.
If solid tantalum input capacitors are used, it is recomended that they
be surge current tested by the manufacturer. The curves shown in Figure 25 can be used to select an appropriate
input capacitor. From the curves, locate the 50V line and note which
Use caution when using ceramic capacitors for input bypassing, capacitor values have RMS current ratings greater than 200 mA. A
because it may cause severe ringing at the VIN pin. 47 μF/50V low ESR electrolytic capacitor capacitor is needed.
For additional information, see EXTERNAL COMPONENTS For a through hole design, a 47 μF/50V electrolytic capacitor
section on input capacitors in Application Information section. (Panasonic HFQ series or Nichicon PL series or equivalent) would
be adequate. Other types or other manufacturers capacitors can be
used provided the RMS ripple current ratings are adequate.
For surface mount designs, solid tantalum capacitors are
recommended. The TPS series available from AVX, and the 593D
series from Sprague are both surge current tested.
To further simplify the buck regulator design procedure, Texas
Instruments is making available computer design software to be
used with the Simple Switcher line to switching regulators.
Switchers Made Simple (version 4.1 or later) is available from TI's
web site, www.ti.com
Table 4. Output Capacitor and Feedforward Capacitor Selection Table
Output Through Hole Output Capacitor Surface Mount Output Capacitor
Voltage Panasonic Nichicon PL Feedforward AVX TPS Sprague Feedforward
(V) HFQ Series Series Capacitor Series 595D Series Capacitor
(μF/V) (μF/V) (μF/V) (μF/V)
1.2 220/25 220/25 0 220/10 220/10 0
4180/25 180/25 4.7 nF 100/10 120/10 4.7 nF
682/25 82/25 4.7 nF 100/10 120/10 4.7 nF
982/25 82/25 3.3 nF 100/16 100/16 3.3 nF
1 2 82/25 82/25 2.2 nF 100/16 100/16 2.2 nF
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Table 4. Output Capacitor and Feedforward Capacitor Selection Table (continued)
Output Through Hole Output Capacitor Surface Mount Output Capacitor
Voltage Panasonic Nichicon PL Feedforward AVX TPS Sprague Feedforward
(V) HFQ Series Series Capacitor Series 595D Series Capacitor
(μF/V) (μF/V) (μF/V) (μF/V)
1 5 82/25 82/25 1.5 nF 68/20 100/20 1.5 nF
2 4 82/50 120/50 1 nF 10/35 15/35 220 pF
2 8 82/50 120/50 820 pF 10/35 15/35 220 pF
LM2594/LM2594HV Series Buck Regulator Design Procedure
INDUCTOR VALUE SELECTION GUIDES
(For Continuous Mode Operation)
Figure 21. LM2594/LM2594HV-3.3 Figure 22. LM2594/LM2594HV-5.0
Figure 23. LM2594/LM2594HV-12 Figure 24. LM2594/LM2594HV-ADJ
Table 5. Inductor Manufacturers Part Numbers
Inductance Current Schott Renco Pulse Engineering Coilcraft
(μH) (A) Through Surface Through Surface Through Surface Surface
Hole Mount Hole Mount Hole Mount Mount
L1 220 0.18 67143910 67144280 RL-5470-3 RL1500-220 PE-53801 PE-53801-S DO1608-224
L2 150 0.21 67143920 67144290 RL-5470-4 RL1500-150 PE-53802 PE-53802-S DO1608-154
L3 100 0.26 67143930 67144300 RL-5470-5 RL1500-100 PE-53803 PE-53803-S DO1608-104
L4 68 0.32 67143940 67144310 RL-1284-68 RL1500-68 PE-53804 PE-53804-S DO1608-68
L5 47 0.37 67148310 67148420 RL-1284-47 RL1500-47 PE-53805 PE-53805-S DO1608-473
L6 33 0.44 67148320 67148430 RL-1284-33 RL1500-33 PE-53806 PE-53806-S DO1608-333
L7 22 0.60 67148330 67148440 RL-1284-22 RL1500-22 PE-53807 PE-53807-S DO1608-223
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Table 5. Inductor Manufacturers Part Numbers (continued)
Inductance Current Schott Renco Pulse Engineering Coilcraft
(μH) (A) Through Surface Through Surface Through Surface Surface
Hole Mount Hole Mount Hole Mount Mount
L8 330 0.26 67143950 67144320 RL-5470-2 RL1500-330 PE-53808 PE-53808-S DO3308-334
L9 220 0.32 67143960 67144330 RL-5470-3 RL1500-220 PE-53809 PE-53809-S DO3308-224
L10 150 0.39 67143970 67144340 RL-5470-4 RL1500-150 PE-53810 PE-53810-S DO3308-154
L11 100 0.48 67143980 67144350 RL-5470-5 RL1500-100 PE-53811 PE-53811-S DO3308-104
L12 68 0.58 67143990 67144360 RL-5470-6 RL1500-68 PE-53812 PE-53812-S DO1608-683
L13 47 0.70 67144000 67144380 RL-5470-7 RL1500-47 PE-53813 PE-53813-S DO3308-473
L14 33 0.83 67148340 67148450 RL-1284-33 RL1500-33 PE-53814 PE-53814-S DO1608-333
L15 22 0.99 67148350 67148460 RL-1284-22 RL1500-22 PE-53815 PE-53815-S DO1608-223
L16 15 1.24 67148360 67148470 RL-1284-15 RL1500-15 PE-53816 PE-53816-S DO1608-153
L17 330 0.42 67144030 67144410 RL-5471-1 RL1500-330 PE-53817 PE-53817-S DO3316-334
L18 220 0.55 67144040 67144420 RL-5471-2 RL1500-220 PE-53818 PE-53818-S DO3316-224
L19 150 0.66 67144050 67144430 RL-5471-3 RL1500-150 PE-53819 PE-53819-S DO3316-154
L20 100 0.82 67144060 67144440 RL-5471-4 RL1500-100 PE-53820 PE-53820-S DO3316-104
L21 68 0.99 67144070 67144450 RL-5471-5 RL1500-68 PE-53821 PE-53821-S DDO3316-683
L26 330 0.80 67144100 67144480 RL-5471-1 — PE-53826 PE-53826-S —
L27 220 1.00 67144110 67144490 RL-5471-2 — PE-53827 PE-53827-S —
Table 6. Inductor Manufacturers Phone Numbers
Coilcraft Inc. Phone (800) 322-2645
FAX (708) 639-1469
Coilcraft Inc., Europe Phone +44 1236 730 595
FAX +44 1236 730 627
Pulse Engineering Inc. Phone (619) 674-8100
FAX (619) 674-8262
Pulse Engineering Inc., Phone +353 93 24 107
Europe FAX +353 93 24 459
Renco Electronics Inc. Phone (800) 645-5828
FAX (516) 586-5562
Schott Corp. Phone (612) 475-1173
FAX (612) 475-1786
Table 7. Capacitor Manufacturers Phone Numbers
Nichicon Corp. Phone (708) 843-7500
FAX (708) 843-2798
Panasonic Phone (714) 373-7857
FAX (714) 373-7102
AVX Corp. Phone (803) 448-9411
FAX (803) 448-1943
Sprague/Vishay Phone (207) 324-7223
FAX (207) 324-4140
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Table 8. Diode Selection Table
VR 1A Diodes
Surface Mount Through Hole
Schottky Ultra Fast Schottky Ultra Fast
Recovery Recovery
20V All of these 1N5817 All of these
diodes are SR102 diodes are
MBRS130 rated to at 1N5818 rated to at
30V least 60V. SR103 least 60V.
11DQ03
MBRS140 MURS120 1N5819 MUR120
40V 10BQ040 10BF10 SR104 HER101
10MQ040 11DQ04 11DF1
50V MBRS160 SR105
or 10BQ050 MBR150
more 10MQ060 11DQ05
MBRS1100 MBR160
10MQ090 SB160
SGL41-60 11DQ10
SS16
Block Diagram
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Application Information
PIN FUNCTIONS
+VIN —This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be
present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator.
Ground —Circuit ground.
Output —Internal switch. The voltage at this pin switches between (+VIN −VSAT) and approximately −0.5V, with
a duty cycle of VOUT/VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this
pin should be kept to a minimum.
Feedback —Senses the regulated output voltage to complete the feedback loop.
ON /OFF —Allows the switching regulator circuit to be shut down using logic level signals thus dropping the total
input supply current to approximately 80 μA. Pulling this pin below a threshold voltage of approximately 1.3V
turns the regulator on, and pulling this pin above 1.3V (up to a maximum of 25V) shuts the regulator down. If this
shutdown feature is not needed, the ON /OFF pin can be wired to the ground pin or it can be left open, in either
case the regulator will be in the ON condition.
EXTERNAL COMPONENTS
CIN —A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground pin. It
must be located near the regulator using short leads. This capacitor prevents large voltage transients from
appearing at the input, and provides the instantaneous current needed each time the switch turns on.
The important parameters for the Input capacitor are the voltage rating and the RMS current rating. Because of
the relatively high RMS currents flowing in a buck regulator's input capacitor, this capacitor should be chosen for
its RMS current rating rather than its capacitance or voltage ratings, although the capacitance value and voltage
rating are directly related to the RMS current rating.
The RMS current rating of a capacitor could be viewed as a capacitor's power rating. The RMS current flowing
through the capacitors internal ESR produces power which causes the internal temperature of the capacitor to
rise. The RMS current rating of a capacitor is determined by the amount of current required to raise the internal
temperature approximately 10°C above an ambient temperature of 105°C. The ability of the capacitor to dissipate
this heat to the surrounding air will determine the amount of current the capacitor can safely sustain. Capacitors
that are physically large and have a large surface area will typically have higher RMS current ratings. For a given
capacitor value, a higher voltage electrolytic capacitor will be physically larger than a lower voltage capacitor, and
thus be able to dissipate more heat to the surrounding air, and therefore will have a higher RMS current rating.
The consequences of operating an electrolytic capacitor above the RMS current rating is a shortened operating
life. The higher temperature speeds up the evaporation of the capacitor's electrolyte, resulting in eventual failure.
Selecting an input capacitor requires consulting the manufacturers data sheet for maximum allowable RMS ripple
current. For a maximum ambient temperature of 40°C, a general guideline would be to select a capacitor with a
ripple current rating of approximately 50% of the DC load current. For ambient temperatures up to 70°C, a
current rating of 75% of the DC load current would be a good choice for a conservative design. The capacitor
voltage rating must be at least 1.25 times greater than the maximum input voltage, and often a much higher
voltage capacitor is needed to satisfy the RMS current requirements.
A graph shown in Figure 25 shows the relationship between an electrolytic capacitor value, its voltage rating, and
the RMS current it is rated for. These curves were obtained from the Nichicon “PL” series of low ESR, high
reliability electrolytic capacitors designed for switching regulator applications. Other capacitor manufacturers offer
similar types of capacitors, but always check the capacitor data sheet.
“Standard” electrolytic capacitors typically have much higher ESR numbers, lower RMS current ratings and
typically have a shorter operating lifetime.
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Because of their small size and excellent performance, surface mount solid tantalum capacitors are often used
for input bypassing, but several precautions must be observed. A small percentage of solid tantalum capacitors
can short if the inrush current rating is exceeded. This can happen at turn on when the input voltage is suddenly
applied, and of course, higher input voltages produce higher inrush currents. Several capacitor manufacturers do
a 100% surge current testing on their products to minimize this potential problem. If high turn on currents are
expected, it may be necessary to limit this current by adding either some resistance or inductance before the
tantalum capacitor, or select a higher voltage capacitor. As with aluminum electrolytic capacitors, the RMS ripple
current rating must be sized to the load current.
Figure 25. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)
OUTPUT CAPACITOR
COUT —An output capacitor is required to filter the output and provide regulator loop stability. Low impedance or
low ESR Electrolytic or solid tantalum capacitors designed for switching regulator applications must be used.
When selecting an output capacitor, the important capacitor parameters are; the 100 kHz Equivalent Series
Resistance (ESR), the RMS ripple current rating, voltage rating, and capacitance value. For the output capacitor,
the ESR value is the most important parameter.
The output capacitor requires an ESR value that has an upper and lower limit. For low output ripple voltage, a
low ESR value is needed. This value is determined by the maximum allowable output ripple voltage, typically 1%
to 2% of the output voltage. But if the selected capacitor's ESR is extremely low, there is a possibility of an
unstable feedback loop, resulting in an oscillation at the output. Using the capacitors listed in the tables, or
similar types, will provide design solutions under all conditions.
If very low output ripple voltage (less than 15 mV) is required, refer to the OUTPUT VOLTAGE RIPPLE AND
TRANSIENTS section for a post ripple filter.
An aluminum electrolytic capacitor's ESR value is related to the capacitance value and its voltage rating. In most
cases, Higher voltage electrolytic capacitors have lower ESR values (see Figure 26 ). Often, capacitors with
much higher voltage ratings may be needed to provide the low ESR values required for low output ripple voltage.
The output capacitor for many different switcher designs often can be satisfied with only three or four different
capacitor values and several different voltage ratings. See the quick design component selection tables in
Figure 24 and Table 4 for typical capacitor values, voltage ratings, and manufacturers capacitor types.
Electrolytic capacitors are not recommended for temperatures below −25°C. The ESR rises dramatically at cold
temperatures and typically rises 3X @ −25°C and as much as 10X at −40°C. See curve shown in Figure 27 .
Solid tantalum capacitors have a much better ESR spec for cold temperatures and are recommended for
temperatures below −25°C.
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Figure 26. Capacitor ESR vs Capacitor Voltage Rating (Typical Low ESR Electrolytic Capacitor)
CATCH DIODE
Buck regulators require a diode to provide a return path for the inductor current when the switch turns off. This
must be a fast diode and must be located close to the LM2594 using short leads and short printed circuit traces.
Because of their very fast switching speed and low forward voltage drop, Schottky diodes provide the best
performance, especially in low output voltage applications (5V and lower). Ultra-fast recovery, or High-Efficiency
rectifiers are also a good choice, but some types with an abrupt turnoff characteristic may cause instability or
EMI problems. Ultra-fast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such
as the 1N4001 series are much too slow and should not be used.
Figure 27. Capacitor ESR Change vs Temperature
INDUCTOR SELECTION
All switching regulators have two basic modes of operation; continuous and discontinuous. The difference
between the two types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for a
period of time in the normal switching cycle. Each mode has distinctively different operating characteristics,
which can affect the regulators performance and requirements. Most switcher designs will operate in the
discontinuous mode when the load current is low.
The LM2594 (or any of the Simple Switcher family) can be used for both continuous or discontinuous modes of
operation.
In many cases the preferred mode of operation is the continuous mode. It offers greater output power, lower
peak switch, inductor and diode currents, and can have lower output ripple voltage. But it does require larger
inductor values to keep the inductor current flowing continuously, especially at low output load currents and/or
high input voltages.
To simplify the inductor selection process, an inductor selection guide (nomograph) was designed (see Figure 21
through Figure 24 ). This guide assumes that the regulator is operating in the continuous mode, and selects an
inductor that will allow a peak-to-peak inductor ripple current to be a certain percentage of the maximum design
load current. This peak-to-peak inductor ripple current percentage is not fixed, but is allowed to change as
different design load currents are selected. (See Figure 28.)
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Figure 28. (ΔIIND) Peak-to-Peak
Inductor Ripple Current
(as a Percentage of the Load Current) vs Load Current
By allowing the percentage of inductor ripple current to increase for low load currents, the inductor value and size
can be kept relatively low.
When operating in the continuous mode, the inductor current waveform ranges from a triangular to a sawtooth
type of waveform (depending on the input voltage), with the average value of this current waveform equal to the
DC output load current.
Inductors are available in different styles such as pot core, toroid, E-core, bobbin core, etc., as well as different
core materials, such as ferrites and powdered iron. The least expensive, the bobbin, rod or stick core, consists of
wire wrapped on a ferrite bobbin. This type of construction makes for a inexpensive inductor, but since the
magnetic flux is not completely contained within the core, it generates more Electro-Magnetic Interference (EMl).
This magnetic flux can induce voltages into nearby printed circuit traces, thus causing problems with both the
switching regulator operation and nearby sensitive circuitry, and can give incorrect scope readings because of
induced voltages in the scope probe. Also see OPEN CORE INDUCTORS section.
The inductors listed in the selection chart include ferrite E-core construction for Schott, ferrite bobbin core for
Renco and Coilcraft, and powdered iron toroid for Pulse Engineering.
Exceeding an inductor's maximum current rating may cause the inductor to overheat because of the copper wire
losses, or the core may saturate. If the inductor begins to saturate, the inductance decreases rapidly and the
inductor begins to look mainly resistive (the DC resistance of the winding). This can cause the switch current to
rise very rapidly and force the switch into a cycle-by-cycle current limit, thus reducing the DC output load current.
This can also result in overheating of the inductor and/or the LM2594. Different inductor types have different
saturation characteristics, and this should be kept in mind when selecting an inductor.
The inductor manufacturers data sheets include current and energy limits to avoid inductor saturation.
DISCONTINUOUS MODE OPERATION
The selection guide chooses inductor values suitable for continuous mode operation, but for low current
applications and/or high input voltages, a discontinuous mode design may be a better choice. It would use an
inductor that would be physically smaller, and would need only one half to one third the inductance value needed
for a continuous mode design. The peak switch and inductor currents will be higher in a discontinuous design,
but at these low load currents (200 mA and below), the maximum switch current will still be less than the switch
current limit.
Discontinuous operation can have voltage waveforms that are considerable different than a continuous design.
The output pin (switch) waveform can have some damped sinusoidal ringing present. (See Figure 17 titled;
Discontinuous Mode Switching Waveforms) This ringing is normal for discontinuous operation, and is not caused
by feedback loop instabilities. In discontinuous operation, there is a period of time where neither the switch or the
diode are conducting, and the inductor current has dropped to zero. During this time, a small amount of energy
can circulate between the inductor and the switch/diode parasitic capacitance causing this characteristic ringing.
Normally this ringing is not a problem, unless the amplitude becomes great enough to exceed the input voltage,
and even then, there is very little energy present to cause damage.
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Different inductor types and/or core materials produce different amounts of this characteristic ringing. Ferrite core
inductors have very little core loss and therefore produce the most ringing. The higher core loss of powdered iron
inductors produce less ringing. If desired, a series RC could be placed in parallel with the inductor to dampen the
ringing. The computer aided design software Switchers Made Simple (version 4.1) will provide all component
values for continuous and discontinuous modes of operation.
Figure 29. Post Ripple Filter Waveform
OUTPUT VOLTAGE RIPPLE AND TRANSIENTS
The output voltage of a switching power supply operating in the continuous mode will contain a sawtooth ripple
voltage at the switcher frequency, and may also contain short voltage spikes at the peaks of the sawtooth
waveform.
The output ripple voltage is a function of the inductor sawtooth ripple current and the ESR of the output
capacitor. A typical output ripple voltage can range from approximately 0.5% to 3% of the output voltage. To
obtain low ripple voltage, the ESR of the output capacitor must be low, however, caution must be exercised when
using extremely low ESR capacitors because they can affect the loop stability, resulting in oscillation problems. If
very low output ripple voltage is needed (less than 15 mV), a post ripple filter is recommended. (See Figure 20.)
The inductance required is typically between 1 μH and 5 μH, with low DC resistance, to maintain good load
regulation. A low ESR output filter capacitor is also required to assure good dynamic load response and ripple
reduction. The ESR of this capacitor may be as low as desired, because it is out of the regulator feedback loop.
The photo shown in Figure 29 shows a typical output ripple voltage, with and without a post ripple filter.
When observing output ripple with a scope, it is essential that a short, low inductance scope probe ground
connection be used. Most scope probe manufacturers provide a special probe terminator which is soldered onto
the regulator board, preferable at the output capacitor. This provides a very short scope ground thus eliminating
the problems associated with the 3 inch ground lead normally provided with the probe, and provides a much
cleaner and more accurate picture of the ripple voltage waveform.
The voltage spikes are caused by the fast switching action of the output switch and the diode, and the parasitic
inductance of the output filter capacitor, and its associated wiring. To minimize these voltage spikes, the output
capacitor should be designed for switching regulator applications, and the lead lengths must be kept very short.
Wiring inductance, stray capacitance, as well as the scope probe used to evaluate these transients, all contribute
to the amplitude of these spikes.
When a switching regulator is operating in the continuous mode, the inductor current waveform ranges from a
triangular to a sawtooth type of waveform (depending on the input voltage). For a given input and output voltage,
the peak-to-peak amplitude of this inductor current waveform remains constant. As the load current increases or
decreases, the entire sawtooth current waveform also rises and falls. The average value (or the center) of this
current waveform is equal to the DC load current.
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If the load current drops to a low enough level, the bottom of the sawtooth current waveform will reach zero, and
the switcher will smoothly change from a continuous to a discontinuous mode of operation. Most switcher
designs (irregardless how large the inductor value is) will be forced to run discontinuous if the output is lightly
loaded. This is a perfectly acceptable mode of operation.
Figure 30. Peak-to-Peak Inductor
Ripple Current vs Load Current
In a switching regulator design, knowing the value of the peak-to-peak inductor ripple current (ΔIIND) can be
useful for determining a number of other circuit parameters. Parameters such as, peak inductor or peak switch
current, minimum load current before the circuit becomes discontinuous, output ripple voltage and output
capacitor ESR can all be calculated from the peak-to-peak ΔIIND. When the inductor nomographs shown in
Figure 21 through Figure 24 are used to select an inductor value, the peak-to-peak inductor ripple current can
immediately be determined. The curve shown in Figure 30 shows the range of (ΔIIND) that can be expected for
different load currents. The curve also shows how the peak-to-peak inductor ripple current (ΔIIND) changes as
you go from the lower border to the upper border (for a given load current) within an inductance region. The
upper border represents a higher input voltage, while the lower border represents a lower input voltage (see
Inductor Selection Guides).
These curves are only correct for continuous mode operation, and only if the inductor selection guides are used
to select the inductor value
Consider the following example:
VOUT = 5V, maximum load current of 300 mA
VIN = 15V, nominal, varying between 11V and 20V.
The selection guide in Figure 22 shows that the vertical line for a 0.3A load current, and the horizontal line for the
15V input voltage intersect approximately midway between the upper and lower borders of the 150 μH
inductance region. A 150 μH inductor will allow a peak-to-peak inductor current (ΔIIND) to flow that will be a
percentage of the maximum load current. Referring to Figure 30, follow the 0.3A line approximately midway into
the inductance region, and read the peak-to-peak inductor ripple current (ΔIIND) on the left hand axis
(approximately 150 mA p-p).
As the input voltage increases to 20V, it approaches the upper border of the inductance region, and the inductor
ripple current increases. Referring to the curve in Figure 30, it can be seen that for a load current of 0.3A, the
peak-to-peak inductor ripple current (ΔIIND) is 150 mA with 15V in, and can range from 175 mA at the upper
border (20V in) to 120 mA at the lower border (11V in).
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SNVS118C –DECEMBER 1999–REVISED APRIL 2013
Once the ΔIIND value is known, the following formulas can be used to calculate additional information about the
switching regulator circuit.
1. Peak Inductor or peak switch current
2. Minimum load current before the circuit becomes discontinuous
3. Output Ripple Voltage
– = (ΔIIND)×(ESR of COUT)
– = 0.150A×0.240Ω=36 mV p-p
– or
4. ESR of COUT
OPEN CORE INDUCTORS
Another possible source of increased output ripple voltage or unstable operation is from an open core inductor.
Ferrite bobbin or stick inductors have magnetic lines of flux flowing through the air from one end of the bobbin to
the other end. These magnetic lines of flux will induce a voltage into any wire or PC board copper trace that
comes within the inductor's magnetic field. The strength of the magnetic field, the orientation and location of the
PC copper trace to the magnetic field, and the distance between the copper trace and the inductor, determine
the amount of voltage generated in the copper trace. Another way of looking at this inductive coupling is to
consider the PC board copper trace as one turn of a transformer (secondary) with the inductor winding as the
primary. Many millivolts can be generated in a copper trace located near an open core inductor which can cause
stability problems or high output ripple voltage problems.
If unstable operation is seen, and an open core inductor is used, it's possible that the location of the inductor with
respect to other PC traces may be the problem. To determine if this is the problem, temporarily raise the inductor
away from the board by several inches and then check circuit operation. If the circuit now operates correctly,
then the magnetic flux from the open core inductor is causing the problem. Substituting a closed core inductor
such as a torroid or E-core will correct the problem, or re-arranging the PC layout may be necessary. Magnetic
flux cutting the IC device ground trace, feedback trace, or the positive or negative traces of the output capacitor
should be minimized.
Sometimes, locating a trace directly beneath a bobbin in- ductor will provide good results, provided it is exactly in
the center of the inductor (because the induced voltages cancel themselves out), but if it is off center one
direction or the other, then problems could arise. If flux problems are present, even the direction of the inductor
winding can make a difference in some circuits.
This discussion on open core inductors is not to frighten the user, but to alert the user on what kind of problems
to watch out for when using them. Open core bobbin or “stick” inductors are an inexpensive, simple way of
making a compact efficient inductor, and they are used by the millions in many different applications.
THERMAL CONSIDERATIONS
The LM2594/LM2594HV is available in two packages, an 8-pin through hole PDIP (P) and an 8-pin surface
mount SOIC-8 (D). Both packages are molded plastic with a copper lead frame. When the package is soldered to
the PC board, the copper and the board are the heat sink for the LM2594 and the other heat producing
components.
For best thermal performance, wide copper traces should be used and all ground and unused pins should be
soldered to generous amounts of printed circuit board copper, such as a ground plane (one exception to this is
the output (switch) pin, which should not have large areas of copper). Large areas of copper provide the best
transfer of heat (lower thermal resistance) to the surrounding air, and even double-sided or multilayer boards
provide a better heat path to the surrounding air. Unless power levels are small, sockets are not recommended
because of the added thermal resistance it adds and the resultant higher junction temperatures.
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Package thermal resistance and junction temperature rise numbers are all approximate, and there are many
factors that will affect the junction temperature. Some of these factors include board size, shape, thickness,
position, location, and even board temperature. Other factors are, trace width, printed circuit copper area, copper
thickness, single- or double-sided, multilayer board, and the amount of solder on the board. The effectiveness of
the PC board to dissipate heat also depends on the size, quantity and spacing of other components on the
board. Furthermore, some of these components such as the catch diode will add heat to the PC board and the
heat can vary as the input voltage changes. For the inductor, depending on the physical size, type of core
material and the DC resistance, it could either act as a heat sink taking heat away from the board, or it could add
heat to the board.
Circuit Data for Temperature Rise Curve (PDIP-8)
Capacitors Through hole electrolytic
Inductor Through hole, Schott, 100 μH
Diode Through hole, 1A 40V, Schottky
PC board 4 square inches single sided 2 oz. copper (0.0028″)
Figure 31. Junction Temperature Rise, PDIP-8
Circuit Data for Temperature Rise Curve
(Surface Mount)
Capacitors Surface mount tantalum, molded “D” size
Inductor Surface mount, Coilcraft DO33, 100 μH
Diode Surface mount, 1A 40V, Schottky
PC board 4 square inches single sided 2 oz. copper (0.0028″)
Figure 32. Junction Temperature Rise, SOIC-8
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SNVS118C –DECEMBER 1999–REVISED APRIL 2013
The curves shown in Figure 31 and Figure 32 show the LM2594 junction temperature rise above ambient
temperature with a 500 mA load for various input and output voltages. This data was taken with the circuit
operating as a buck switcher with all components mounted on a PC board to simulate the junction temperature
under actual operating conditions. This curve is typical, and can be used for a quick check on the maximum
junction temperature for various conditions, but keep in mind that there are many factors that can affect the
junction temperature.
Figure 33. Delayed Startup
Figure 34. Undervoltage Lockout
for Buck Regulator
DELAYED STARTUP
The circuit in Figure 33 uses the the ON /OFF pin to provide a time delay between the time the input voltage is
applied and the time the output voltage comes up (only the circuitry pertaining to the delayed start up is shown).
As the input voltage rises, the charging of capacitor C1 pulls the ON /OFF pin high, keeping the regulator off.
Once the input voltage reaches its final value and the capacitor stops charging, and resistor R2pulls the ON
/OFF pin low, thus allowing the circuit to start switching. Resistor R1is included to limit the maximum voltage
applied to the ON /OFF pin (maximum of 25V), reduces power supply noise sensitivity, and also limits the
capacitor, C1, discharge current. When high input ripple voltage exists, avoid long delay time, because this ripple
can be coupled into the ON /OFF pin and cause problems.
This delayed startup feature is useful in situations where the input power source is limited in the amount of
current it can deliver. It allows the input voltage to rise to a higher voltage before the regulator starts operating.
Buck regulators require less input current at higher input voltages.
UNDERVOLTAGE LOCKOUT
Some applications require the regulator to remain off until the input voltage reaches a predetermined voltage. An
undervoltage lockout feature applied to a buck regulator is shown in Figure 34, while Figure 35 and Figure 36
applies the same feature to an inverting circuit. The circuit in Figure 35 features a constant threshold voltage for
turn on and turn off (zener voltage plus approximately one volt). If hysteresis is needed, the circuit in Figure 36
has a turn ON voltage which is different than the turn OFF voltage. The amount of hysteresis is approximately
equal to the value of the output voltage. If zener voltages greater than 25V are used, an additional 47 kΩresistor
is needed from the ON /OFF pin to the ground pin to stay within the 25V maximum limit of the ON /OFF pin.
INVERTING REGULATOR
The circuit in Figure 37 converts a positive input voltage to a negative output voltage with a common ground. The
circuit operates by bootstrapping the regulators ground pin to the negative output voltage, then grounding the
feedback pin, the regulator senses the inverted output voltage and regulates it.
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SNVS118C –DECEMBER 1999–REVISED APRIL 2013
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This circuit has an ON/OFF threshold of approximately 13V.
Figure 35. Undervoltage Lockout for Inverting Regulator
This circuit has hysteresis
Regulator starts switching at VIN = 13V
Regulator stops switching at VIN = 8V
Figure 36. Undervoltage Lockout with Hysteresis for Inverting Regulator
CIN — 68 μF/25V Tant. Sprague 595D
120 μF/35V Elec. Panasonic HFQ
COUT — 22 μF/20V Tant. Sprague 595D
39 μF/16V Elec. Panasonic HFQ
Figure 37. Inverting −5V Regulator with Delayed Startup
This example uses the LM2594-5 to generate a −5V output, but other output voltages are possible by selecting
other output voltage versions, including the adjustable version. Since this regulator topology can produce an
output voltage that is either greater than or less than the input voltage, the maximum output current greatly
depends on both the input and output voltage. The curve shown in Figure 38 provides a guide as to the amount
of output load current possible for the different input and output voltage conditions.
The maximum voltage appearing across the regulator is the absolute sum of the input and output voltage, and
this must be limited to a maximum of 40V. For example, when converting +20V to −12V, the regulator would see
32V between the input pin and ground pin. The LM2594 has a maximum input voltage spec of 40V (60V for the
LM2594HV).
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SNVS118C –DECEMBER 1999–REVISED APRIL 2013
Additional diodes are required in this regulator configuration. Diode D1 is used to isolate input voltage ripple or
noise from coupling through the CIN capacitor to the output, under light or no load conditions. Also, this diode
isolation changes the topology to closley resemble a buck configuration thus providing good closed loop stability.
A Schottky diode is recommended for low input voltages, (because of its lower voltage drop) but for higher input
voltages, a fast recovery diode could be used.
Without diode D3, when the input voltage is first applied, the charging current of CIN can pull the output positive
by several volts for a short period of time. Adding D3 prevents the output from going positive by more than a
diode voltage.
Figure 38. Inverting Regulator Typical Load Current
Because of differences in the operation of the inverting regulator, the standard design procedure is not used to
select the inductor value. In the majority of designs, a 100 μH, 1A inductor is the best choice. Capacitor selection
can also be narrowed down to just a few values. Using the values shown in Figure 37 will provide good results in
the majority of inverting designs.
This type of inverting regulator can require relatively large amounts of input current when starting up, even with
light loads. Input currents as high as the LM2594 current limit (approx 0.8A) are needed for at least 2 ms or
more, until the output reaches its nominal output voltage. The actual time depends on the output voltage and the
size of the output capacitor. Input power sources that are current limited or sources that can not deliver these
currents without getting loaded down, may not work correctly. Because of the relatively high startup currents
required by the inverting topology, the delayed startup feature (C1, R1and R2) shown in Figure 37 is
recommended. By delaying the regulator startup, the input capacitor is allowed to charge up to a higher voltage
before the switcher begins operating. A portion of the high input current needed for startup is now supplied by the
input capacitor (CIN). For severe start up conditions, the input capacitor can be made much larger than normal.
INVERTING REGULATOR SHUTDOWN METHODS
To use the ON /OFF pin in a standard buck configuration is simple, pull it below 1.3V (@25°C, referenced to
ground) to turn regulator ON, pull it above 1.3V to shut the regulator OFF. With the inverting configuration, some
level shifting is required, because the ground pin of the regulator is no longer at ground, but is now setting at the
negative output voltage level. Two different shutdown methods for inverting regulators are shown in Figure 39
and Figure 40.
Figure 39. Inverting Regulator Ground Referenced Shutdown
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Figure 40. Inverting Regulator Ground Referenced Shutdown using Opto Device
Figure 41. TYPICAL SURFACE MOUNT PC BOARD LAYOUT, FIXED OUTPUT (2X SIZE)
CIN —10 μF, 35V, Solid Tantalum AVX, “TPS series”
COUT —100 μF, 10V Solid Tantalum AVX, “TPS series”
D1 — 1A, 40V Schottky Rectifier, surface mount
L1 — 100 μH, L20, Coilcraft DO33
Figure 42. TYPICAL SURFACE MOUNT PC BOARD LAYOUT, ADJUSTABLE OUTPUT (2X SIZE)
CIN —10 μF, 35V, Solid Tantalum AVX, “TPS series”
COUT —100 μF, 10V Solid Tantalum AVX, “TPS series”
D1 — 1A, 40V Schottky Rectifier, surface mount
L1 — 100 μH, L20, Coilcraft DO33
R1 — 1 kΩ, 1%
R2—Use formula in Design Procedure
CFF —See Table 4.
30 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated
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SNVS118C –DECEMBER 1999–REVISED APRIL 2013
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REVISION HISTORY
Changes from Revision B (April 2013) to Revision C Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 31
32 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated
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PACKAGE OPTION ADDENDUM
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Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM2594HVM-12 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594H
M-12
LM2594HVM-12/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594H
M-12
LM2594HVM-3.3 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594H
M-3.3
LM2594HVM-3.3/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594H
M-3.3
LM2594HVM-5.0 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594H
M-5.0
LM2594HVM-5.0/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594H
M-5.0
LM2594HVM-ADJ NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594H
M-ADJ
LM2594HVM-ADJ/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594H
M-ADJ
LM2594HVMX-12/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594H
M-12
LM2594HVMX-3.3 NRND SOIC D 8 2500 TBD Call TI Call TI -40 to 125 2594H
M-3.3
LM2594HVMX-3.3/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594H
M-3.3
LM2594HVMX-5.0 NRND SOIC D 8 2500 TBD Call TI Call TI -40 to 125 2594H
M-5.0
LM2594HVMX-5.0/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594H
M-5.0
LM2594HVMX-ADJ/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594H
M-ADJ
LM2594HVN-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2594HV
N-12 P+
LM2594HVN-3.3/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2594HV
N-3.3 P+
LM2594HVN-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2594HV
N-5.0 P+
PACKAGE OPTION ADDENDUM
www.ti.com 1-Nov-2013
Addendum-Page 2
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM2594HVN-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2594HV
N-ADJ P+
LM2594M-12 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594
M-12
LM2594M-12/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594
M-12
LM2594M-3.3 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594
M-3.3
LM2594M-3.3/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594
M-3.3
LM2594M-5.0 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594
M-5.0
LM2594M-5.0/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594
M-5.0
LM2594M-ADJ/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594
M-ADJ
LM2594MX-12/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2594
M-12
LM2594MX-3.3/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594
M-3.3
LM2594MX-5.0/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594
M-5.0
LM2594MX-ADJ NRND SOIC D 8 2500 TBD Call TI Call TI -40 to 125 2594
M-ADJ
LM2594MX-ADJ/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br) SN | CU SN Level-1-260C-UNLIM -40 to 125 2594
M-ADJ
LM2594N-12 NRND PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2594N
-12 P+
LM2594N-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br) CU SN | Call TI Level-1-NA-UNLIM -40 to 125 LM2594N
-12 P+
LM2594N-3.3/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br) CU SN | Call TI Level-1-NA-UNLIM -40 to 125 LM2594N
-3.3 P+
LM2594N-5.0 NRND PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2594N
-5.0 P+
LM2594N-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2594N
-5.0 P+
PACKAGE OPTION ADDENDUM
www.ti.com 1-Nov-2013
Addendum-Page 3
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM2594N-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2594N
-ADJ P+
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LM2594HVMX-12/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594HVMX-3.3 SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594HVMX-3.3/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594HVMX-5.0 SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594HVMX-5.0/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594HVMX-ADJ/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594MX-12/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594MX-3.3/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594MX-5.0/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594MX-ADJ SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
LM2594MX-ADJ/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 11-Oct-2013
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM2594HVMX-12/NOPB SOIC D 8 2500 367.0 367.0 35.0
LM2594HVMX-3.3 SOIC D 8 2500 367.0 367.0 35.0
LM2594HVMX-3.3/NOPB SOIC D 8 2500 367.0 367.0 35.0
LM2594HVMX-5.0 SOIC D 8 2500 367.0 367.0 35.0
LM2594HVMX-5.0/NOPB SOIC D 8 2500 367.0 367.0 35.0
LM2594HVMX-ADJ/NOPB SOIC D 8 2500 367.0 367.0 35.0
LM2594MX-12/NOPB SOIC D 8 2500 367.0 367.0 35.0
LM2594MX-3.3/NOPB SOIC D 8 2500 367.0 367.0 35.0
LM2594MX-5.0/NOPB SOIC D 8 2500 367.0 367.0 35.0
LM2594MX-ADJ SOIC D 8 2500 367.0 367.0 35.0
LM2594MX-ADJ/NOPB SOIC D 8 2500 367.0 367.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 11-Oct-2013
Pack Materials-Page 2
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