Applications Information
Capacitor Selection
The type of capacitor used is not critical for proper
operation. Ceramic capacitors are suggested. To ensure
proper RS-232 signal levels over temperature when
using 0.1µF capacitors, make sure the capacitance value
does not degrade excessively as the temperature varies.
If in doubt, use capacitors with a larger nominal value.
Also observe the capacitors’ ESR value over tempera-
ture, since it influences the amount of ripple on V+ and
V-. To reduce the output impedance at V+ and V-, use
larger capacitors (up to 10µF). If polarized capacitors are
used, obey the polarities shown in Figure 1 and the pin
configurations.
Driving Multiple Receivers
Each transmitter is designed to drive a single receiver.
Transmitters can be paralleled to drive multiple receivers.
Driver Outputs When Exiting Shutdown
Figure 5 shows two driver outputs exiting shutdown. As
they become active, the two driver outputs go to opposite
RS-232 levels (one driver input is high, the other is low).
Each driver is loaded with 3kΩ in parallel with 2500pF.
The driver outputs display no ringing or undesirable tran-
sients as they come out of shutdown.
Power-Supply Decoupling
In applications that are sensitive to power-supply noise,
decouple VCC to ground with a capacitor of the same
value as the charge-pump capacitors.
V+ and V- as Power Supplies
A small amount of power can be drawn from V+ and V-,
although this reduces noise margins.
Power Supplies for MAX201/MAX209
If at power-up the V+ supply rises after the VCC supply,
place a diode (e.g., 1N914) in series with the V+ supply.
Table 2. Summary of EIA/TIA-232E, V.28 Specifications
Table 3. DB9 Cable Connections Commonly Used for EIA/TIA-232E and V.24
Asynchronous Interfaces
PARAMETER CONDITION EIA/TIA-232E, V.28 SPECIFICATION
Driver Output Voltage: 0 Level 3kΩ to 7kΩ load +5.0V to +15V
Driver Output Voltage: 1 Level 3kΩ to 7kΩ load -5.0V to -15V
Output Level, Maximum No load ±25V
Data Rate 3kΩ ≤ RL ≤ 7kΩ, CL ≤ 2500pF Up to 20kbps
Receiver Input Voltage: 0 Level — +3.0V to +15V
Receiver Input Voltage: 1 Level — -3.0V to -15V
Input Level, Maximum — ±25V
Instantaneous Slew Rate, Maximum 3kΩ ≤ RL ≤ 7kΩ, CL ≤ 2500pF 30V/µs
Driver Output Short-Circuit Current, Maximum — 100mA
Transition Rate on Driver Output V.28 1ms or 3% of the period
EIA/TIA-232E 4% of the period
Driver Output Resistance -2V < VOUT < +2V 300Ω
PIN NAME CONNECTION
1 Received Line Signal Detector, sometimes called Carrier Detect (DCD) Handshake from DCE
2 Receive Data (RD) Data from DCE
3 Transmit Data (TD) Data from DTE
4Data Terminal Ready Handshake from DTE
5 Signal Ground Reference point for signals
6 Data Set Ready (DSR) Handshake from DCE
7 Request to Send (RTS) Handshake from DTE
8 Clear to Send (CTS) Handshake from DCE
9 Ring Indicator Handshake from DCE
MAX200–MAX209/
MAX211/MAX213
+5V, RS-232 Transceivers
with 0.1μF External Capacitors
www.maximintegrated.com Maxim Integrated
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