LinearTechnologyChronicle A Showcase of Linear Technology's Focus Products October 1996 Products of the Month High Speed Parallel 12-Bit ADCs Deliver on Performance While Consuming Only Milliwatts The 1.25Msps LTC(R)1415 and 800ksps LTC1409 are 12-bit ADCs with wideband sample-and-holds and precision references that consume minimal amounts of power. The LTC1415 has 72dB signal-to-(noise + distortion) ratio (SINAD) and 80dB THD at an input frequency of 100kHz. It operates off a single 5V supply and dissipates only 55mW (typ) while converting at 1.25Msps. The LTC1409 has a guaranteed AC performance of 71dB SINAD and 82dB THD at the Nyquist input frequency of 400kHz over temperature. It accepts 2.5V inputs and dissipates only 80mW (typ) while converting at 800ksps. In sleep mode, these ADCs consume just 10W and in nap mode only 7.5mW and 4mW, respectively. They recover from nap mode in 200ns allowing reduced power consumption during brief 12 inactive periods. DC specifications include a maximum INL and DNL of 1LSB over temperature. Figure 2 shows the excellent typical DNL performance for the LTC1415. The LTC1409 and LTC1415 excel in applications that must digitize fast moving signals with outstanding spectral purity. The sample-and-hold has a high impedance differential input that rejects wideband common mode noise by 60dB, simplifying front-end signal conditioning design. The internal precision references can be used for external circuitry or overridden by an external source to improve temperature or time stability. The three-state parallel interface easily connects to popular DSP and microprocessor parallel ports. The LTC1409 and LTC1415 do not have a pipeline delay such as found with 74 1.0 Vol. 5 No. 10 multistep architectures. Each conversion cycle yields results that correlate to the analog input at the time the sample command was issued. This is a big advantage for multiplexed process control and robotics applications or for event capture systems. They are also ideally suited for demanding telecom, IF down conversion, undersampling and high speed data acquisition applications. Low power dissipation permits use in battery-powered and portable applications. The LTC1415 joins the 1.25Msps LTC1410, introduced last year as LTC's fastest 12-bit high speed parallel A/D converter. This growing family of ADCs is offered in 28-lead SW packages and has similar pinouts, allowing a single layout to accommodate any of the three devices. For a data sheet and evaluation samples of each of these high performance ADCs, contact your local Linear Technology sales office. Low Power 8th Order Elliptic Lowpass Filter in SO-8 Needs Only 3V Supply 68 56 8 50 6 4 DNL EOC ERROR (LSB) 62 NYQUIST FREQUENCY S/(N + D) (dB) EFFECTIVE BITS 10 0.5 0 -0.5 2 fSAMPLE = 800ksps 0 1k 10k 100k 1M INPUT FREQUENCY (Hz) 10M -1.0 LTC1409 * TA02 Figure 1. LTC1409 Has 71dB SINAD at the Nyquist Input Frequency of 400kHz 0 512 1024 1536 2048 2560 3072 3584 4095 CODE 1415 TA02 Figure 2. LTC1415 Has a Typical Differential Nonlinearity (DNL) of Only 0.25LSB Inside This Issue: Low Power Quad 12-Bit Rail-to-Rail DACs Have DNL of Only 0.5LSB ................................ 2 An Open-Architecture Ring-Tone Generator .......................................................................... 3 Inductorless Switched Capacitor Converter Delivers 60mA at 12V from 5V Source .............. 4 Quad C-LoadTM JFET Op Amps Offer Power Savings and Picoampere Inputs ...................... 4 , LTC and LT are registered trademarks of Linear Technology Corporation. C-Load is a trademark of Linear Technology Corporation. Linear Technology Chronicle * October 1996 The LTC1069-6 is a low power 8th order, elliptic lowpass filter optimized for single 3V or 5V supply operation. The low supply voltage operation of the LTC1069-6 does not penalize dynamic range. It achieves a 79dB signal-to-noise ratio (S/N) and a cutoff frequency of 20kHz under 5V operation, while drawing just 1.2mA (typ) of supply current. With a single 3V supply, it has a 14kHz cutoff frequency, a 72dB S/N and typically draws just 1mA of supply current. No external components are required except for power supply bypass capacitors. Cutoff frequency is clock tunable and equals the clock frequency divided by 50. The input signal is sampled twice per clock cycle to lower the risk of aliasing. The stopband attenuation has a progressive elliptic response reaching 42dB attenuation at 1.3 x fCUTTOFF, 66dB at 2.0 x fCUTTOFF, and over 70dB at 2.1 x fCUTTOFF. The gain at fCUTOFF is - 0.07dB and typical passband Continued on page 2 1 -45 10 LTC1069-6 from page 1 ripple is only 0.1dB. Figure 1 shows the 3V frequency response of the LT1069-6 for a 500mVRMS input. Figure 2 shows the dynamic range under 5V operation. These features make it a good choice for precision telecommunications and antialiasing applications, or other filter applications where a compact solution is required. The LTC1069-6 is immediately available in volume from stock in an SO-8 surface mount package over the commercial and industrial temperature ranges. Contact your local Linear Technology sales office for a data sheet and evaluation samples. REFOUT CS/LD CLK THD + NOISE (dB) -55 GAIN (dB) -20 -30 -40 -50 -60 -65 -70 -75 -60 -80 -70 -85 0.1 -80 10 5 20 15 FREQUENCY (kHz) 25 1 INPUT VOLTAGE (VRMS) 2 LTC1069-6 * TA03 LTC1069-6 * TA02 The LTC1458/LTC1458L are quad 12-bit DACs, complete with rail-to-rail amplifiers and references for single 5V and 3V supply applications. They have a maximum differential nonlinearity (DNL) of only 0.5LSB for guaranteed 12-bit monotonic performance. The 5V LTC1458, shown in Figure 1, typically draws just 1100A while the 3V LTC1458L draws only 800A. They are ideal in feedback loops of digital control systems, such as calibration DACs in industrial control systems and for large distributed power supplies, where multiple inexpensive D/A devices are required. Their low power consumption also make them suitable in por- FROM P fIN = 1kHz fC = 5kHz -50 -10 Low Power Quad 12-Bit Rail-to-Rail DACs Have DNL of Only 0.5LSB 2.048V (LTC1458) 1.22V (LTC1458L) VIN = 500mVRMS 0 Figure 1. Frequency Response of LTC1069-6 10kHz Elliptic Lowpass Filter with Single 3V Supply Figure 2. THD + Noise Characteristics of LTC1069-6 with 5V Supply table battery-powered digitally controlled instruments where minimal power dissipation is key. The LTC1458/58L include an output buffer amplifier with variable gain (x1 or x 2) and 3-wire serial interface, which is SPI, QSPI and MICROWIRETM compatible. The serial interface eases the connection to microcontrollers and microprocessors with built-in SPI ports and reduces I/O lines in remote or isolated applications. The rail-torail amplifiers ensure an accurate full-scale output even when driving heavy loads on reduced supply voltages and have improved capacitive load handling when compared to competing devices. Power-on reset ensures that the outputs are at zero scale when powered up. The on-chip reference (2.048V for the LTC1458; 1.220V for LTC1458L) is brought out, allowing it to be used for exter- nal circuitry and is not internally connected. This allows a user specified external reference to be used for all DACs. The asynchronous Clear pin resets all DACs to zero scale on command. This can be useful in system initialization and interrupt processing schemes. The ability to select the output amplifiers gain and output ground reference allows virtually any output range within the constraints of the power supply. Figure 2 shows the DNL characteristics of the LTC1458. The LTC1458/58L are offered in 28-pin SO and SSOP packages. Both devices are available from stock screened to the commercial and industrial temperature. Call your local Linear Technology sales office for a data sheet and evaluation samples. MICROWIRE is a trademark of National Semiconductor Corp. 5V (LTC1458) 3V TO 5V (LTC1458L) DIN VCC 0.5 REFHI C REFHI B 0.4 0.3 DAC C X1/X2 C DAC B 48-BIT REFLO C 0.2 X1/X2 B 0.1 REFLO B SHIFT REGISTER AND REFHI D VOUT B REFHI A DAC REGISTER VOUT D DAC D DAC A VOUT A X1/X2 D X1/X2 A REFLO D REFLO A CLR 1458 BD01 2 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 DOUT Figure 1. Functional Block Diagram: Quad 12-Bit Rail-to-Rail DAC DNL (LSB) VOUT C 512 1024 1536 2048 2560 3072 3584 4095 CODE 1458 G09 Figure 2. Differential Nonlinearity vs Input Code for LTC1458--Max DNL is Less Than 0.5LSB Linear Technology Chronicle * October 1996 Application of the Month An Open-Architecture Ring-Tone Generator When a phone rings, it rings with a cadence, a sequence of rings and pauses. The standard cadence is one second ringing followed by two seconds of silence. We use the first 1/4 of an LT(R)1491 as a cadence oscillator, whose output is at VCC for one second and then at VEE for two seconds. This sequence repeats every three seconds, producing the all-toofamiliar pattern. The actual ringing of the bell is done by a 20Hz AC sine wave signal at a signal level of 87VRMS superimposed on - 48VDC. The 20Hz signal is implemented with the second amplifier in the LT1491 which acts as a gated 20Hz oscillator (see Figure 1). The third amplifier in the LT1491, which is configured as a lowpass filter, converts the square wave output of the oscillator to a sine wave by filtering out unwanted harmonics. Finally, the 87VRMS and the - 48VDC parts are handled by the fourth amplifier in the LT1491 and its steering of two external 15V regulators. The rest of what we do, the part that is most difficult to follow, involves the output amplifier. In the output amplifier, the 6VP-P signal from the waveform synthesizer is imposed across R12 (see Figure 2) into a virtual ground, creating a sine wave signal current. This current is added to the DC current flowing through R15 and the resulting 10k 33k 10k - F + 47k 0.068 620k 100K + 300k - 1N4148 1.6M + 620k 16k 0.47 F 1F GATED SINE WAVE OUTPUT LT1491 150k LT1491 LT1491 - current is imposed across R13. This stage amplifies the sine wave and offsets it to become an 87VRMS sine wave imposed on a - 48VDC bias. The trick here is that the voltage gain is in the 15V regulators, not the LT1491 which is merely steering currents. This complete circuit (Figure 2) includes the ring-trip sense circuit to detect when the phone receiver is picked up. This circuit is fully protected for output shorts to any voltage within the power supply window of -180V to 60V. 0.47 F REPRESENTS FLOATING GROUND NOT EQUAL TO OR F F V- DN134 F03 Figure 1. Waveform Synthesizer 60V R16 100k R2 47k R3 10k C2 0.47F 3 R1 33k 2 + U1A LT1491 1 D1 1N4148 R5 100k 5 Q1 IRF628 R6 10k + U1B LT1491 6 - 7 R9 300k R7 16k - R11 10k C4 0.068F 10 9 Z1 15V 100k + U1C LT1491 8 13 - 12 C1 1F R4 1.6M R8 620k CADENCE OSCILLATOR Q3 2N3904 C3 0.047F 20Hz OSCILLATOR R12 R10 SMOOTHING FILTER 10k 620k R14 10k R13 130k R15 47k C5 0.01F 4 - U1D LT1491 + R24 420 11 14 C7 47F R18 100 R23 4.7k R26 2k OPTO1 * R25 4.7k Q5 2N3904 Z2 15V *LED OF OPTO1 ILLUMINATES WHEN THE PHONE IS OFF THE HOOK R17 620 Q2 IRF9620 POWER AMPLIFIER -180 R20 100K UP TO LOAD TEN PHONES R19 620 Q4 2N3906 R21 150 C6 0.033F DN134 F04 Figure 2. Complete Ring-Tone Generator Circuit Linear Technology Chronicle * October 1996 3 Inductorless Switched Capacitor Converter Delivers 60mA at 12V from 5V Source VCC 4.75V TO 5.5V 13.0 12.8 OUTPUT VOLTAGE (V) 12.6 10F 12.4 SHDN C1- 12.2 C2 0.47F 0 C2 100nF 40 60 80 LOAD CURRENT (mA) 3 10F 100 LTC1263 * TA01 50mV/DIV The LTC1263's low shutdown current and lack of a DC current path from input to output are additional battery-saving advantages over inductor-based micropower boost switchers. The LTC1263 is available in an SO-8 package. For a data sheet and evaluation samples, contact your local Linear Technology sales office. 0V 1464 G18 5s/DIV AV = 1 CL = 100pF Figure 1. Small-Signal Response, VS = 5V, 15V, CLOAD = 1000pF amplifiers offer tremendous power savings--extending battery life and allowing more compact designs by running cooler than other JFETs. They are ideally suited for battery-powered systems, photo current amplifiers and as low frequency, micropower active filters. Figure 2 shows the LT1465 configured as a Chebyshev lowpass filter. The LT1463 and the LT1465 are offered in standard 14-pin PDIP and SO packages. For a data sheet and evaluation samples, get in touch with your local Linear Technology sales office. These amplifiers are stable while driving capacitive loads up to 10nF (10,000pF). In addition, the input common mode range includes the positive rail. These quad JFET Linear Technology Products Are Distributed By: C3 10nF 4 1 R4 154k R6 249k 13 - 12 + + 11 GND VPP generate the 12V output. Figure 1 shows the output voltage vs load current for a 5V input. It packs this conversion power into an SO-8 package and requires only four external components (see Figure 2), all of which are small ceramic capacitors (two 0.47F and two 10F). Usually an inductor is required to boost a 5V source to a 12V output with a current of over 30mA--greatly increasing the physical size of the DC/DC converter. R5 154k 1/4 LT1465 VOUT FLASH MEMORY Figure 2. Flash Memory Programming Supply Using the LTC1263 15V - C2+ 5V Figure 1. Output Voltage vs Load Characteristics for LTC1263 C1 33nF VIN 20 - LTC1263 * TA02 R2 237k 2 12V LTC1263 11.6 11.0 The LT1463 and the LT1465 are quad JFET input amplifiers that represent an important addition to LTC's family of low power JFETs. These new JFET op amps are quad versions of the LT1462 and LT1464 duals introduced last month in Linear Technology Chronicle. The LT1463 has a slew rate of 0.13V/s and 175kHz bandwidth. The LT1465 has a slew rate of 0.9V/s and a bandwidth of 1MHz. Figure 1 shows the small-signal response of the LT1465. R3 249k P ON C1+ 11.8 11.2 Quad C-Load JFET Op Amps Offer Power Savings and Picoampere Inputs R1 237k SHDN 0.47F 12.0 11.4 The LTC1263 is a switched capacitor charge pump converter which converts a 4.75V to 5.5V input to a regulated 12V output voltage without using inductors. It delivers up to 60mA of output current at 5V with 76% efficiency. The LTC1263 typically draws only 300A of supply current while converting, and just 1mA max under quiescent conditions. A shutdown pin further reduces the supply current to less than 1A, making it suitable for portable and battery-operated applications. It is ideal for 12V flash memory supplies in PCMCIA cards, as well as for amplifier or data conversion supplies in portable, handheld devices and instruments. The LTC1263 uses a charge pump tripler, clocked by an internal oscillator, to VCC C4 330nF 1/4 LT1465 14 VOUT LT1464 * TA05 -15V TYPICAL OFFSET 0.6mV 1% TOLERANCES FOR VIN = 10VP-P,V OUT = -110dB AT f > 300Hz V OUT = -6dB AT f = 16Hz THE LOW INPUT BIAS CURRENTS ALLOW THE USE OF HIGH RESISTOR VALUES Figure 2. LT1465 JFET Input Op Amp as a 10MHz 4th Order Chebyshev Lowpass Filter (0.01dB Ripple) Almac/Arrow Arrow/Schweber Arrow/Zeus Digi-Key Electrosonic Gerber Electronics Farnell Electronics Marshall Industries Phase 1 (c) 1996 Linear Technology Corporation/Printed in USA 4 Technology Corporation * 1630 McCarthy Blvd. * Milpitas, California 95035-7417 * (408) 432-1900 * FAX: Linear (408) 434-0507 * ForChronicle Literature Only: 1-800-4-LINEAR Linear Technology * October 1996