19-2318; Rev 0; 1/02 Precision Resistor Network for Programmable Instrumentation Amplifiers Features ♦ Differential Gains: AV = 1, 2, 4, 8 ♦ Gain Accurate to 0.025%, 0.09%, or 0.5% ♦ Dual Supply ±5V to ±15V Operation ♦ Low 36µA Supply Current ♦ Simple CMOS/TTL Logic Compatible 2-Wire Parallel Interface ♦ Space-Saving 14-Pin TSSOP Package (6.4mm ✕ 5mm) ♦ OFFSET Pin Available to Offset the Output of the Differential Amplifier Applications Ordering Information General-Purpose Programmable Instrumentation Amplifiers TEMP RANGE PINPACKAGE GAIN MAX5426AEUD -40°C to +85°C 14 TSSOP 0.025% MAX5426BEUD -40°C to +85°C 14 TSSOP 0.09% MAX5426CEUD -40°C to +85°C 14 TSSOP 0.5% PART Gain Control in RF Power Amplifiers Precision Dual Attenuator Pin Configuration and Functional Diagram appear at end of data sheet. Typical Operating Circuit VIN- FB1 VDD OUT1 INDIF- D0 OUT D1 VOUT CM MAX5426 OFFSET VSS GND FB2 OUT2 INDIF+ VIN+ ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX5426 General Description The MAX5426 is a precision resistor network optimized for use with programmable instrumentation amplifiers. The MAX5426 operates from dual ±5V to ±15V supplies and consumes less than 40µA of supply current. Designed to be used in the traditional three op amp instrumentation amplifier topology, this device provides noninverting gains of 1, 2, 4, and 8 that are accurate to 0.025% (A-grade), 0.09% (B-grade), or 0.5% (C-grade) over the extended temperature range (-40°C to +85°C). The MAX5426 is available in the 6.4mm ✕ 5mm 14-pin TSSOP package. MAX5426 Precision Resistor Network for Programmable Instrumentation Amplifiers ABSOLUTE MAXIMUM RATINGS VDD to GND ............................................................-0.3V to +17V VSS to GND.............................................................-17V to +0.3V D0, D1 to GND ...........................................-0.3V to (VDD + 0.2V) D0, D1 to GND (VDD > +6V) .................................-0.3V to +6.0V All Other Pins to GND ......................(VSS - 0.3V) to (VDD + 0.2V) Maximum Current Into VDD, VSS, D1, D0 .........................±50mA Maximum Current from OUT1 to CM or OUT2 ..............±0.72mA Maximum Current from OUT1 to INDIF- or OUT............±0.72mA Maximum Current from OUT2 to INDIF+ or OFFSET.....±0.72mA Continuous Power Dissipation (TA = +70°C) 14-Pin TSSOP (derate 9.1mW/°C above +70°C) ..........727mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-60°C to +150°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VDD = +15V, VSS = -15V, GND = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL Gain Range Accuracy (Notes 1, 2) Capacitance at Analog Pins CONDITIONS MIN TYP MAX MAX5426A 0.004 0.025 MAX5426B 0.025 0.090 MAX5426C 0.080 0.500 CANALOG Differential CMRR (Notes 1, 2) 5 Gain = 1 79 Gain = 2 85 Gain = 4 91 Gain = 8 97 UNITS % pF dB DIGITAL INPUTS Input High Voltage VIH Input Low Voltage VIL Input Leakage Current ILKG 2.4 V D1 = D0 = 0 or logic high 0.8 V 10 µA EQUIVALENT RESISTANCES Resistance Between OUT1 and OUT2 ROUT1, ROUT2 56 kΩ Resistance Between OUT1 and INDIF- ROUT1, RINDIF- 26 kΩ Resistance Between INDIF- and OUT RINDIF-, ROUT 26 kΩ Resistance Between OUT2 and INDIF+ ROUT2, RINDIF+ 26 kΩ RINDIF+, ROFFSET 26 kΩ Resistance Between INDIF+ and OFFSET Resistance Between OUT1 and FB1 2 ROUT1, RFB1 Gain = 1 0 Gain = 2 15 Gain = 4 22 Gain = 8 26 _______________________________________________________________________________________ kΩ Precision Resistor Network for Programmable Instrumentation Amplifiers (VDD = +15V, VSS = -15V, GND = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Resistance Between FB1 and FB2 (Note 3) Resistance Between OUT2 and FB2 SYMBOL RFB1, RFB2 ROUT2, RFB2 Input Impedance at FB1 ZFB1 Input Impedance at FB2 ZFB2 Input Impedance at OUT1 (Note 4) Input Impedance at OUT2 (Note 4) ZOUT1 ZOUT2 CONDITIONS MIN TYP Gain = 2 29 Gain = 4 15 Gain = 8 7 Gain = 1 0 Gain = 2 15 Gain = 4 22 Gain = 8 26 MAX UNITS kΩ kΩ 0 kΩ 0 kΩ Gain = 1 0 Gain = 2 9.5 Gain = 4 12 Gain = 8 13 Gain = 1 0 Gain = 2 9.5 Gain = 4 12 Gain = 8 13 kΩ kΩ Input Impedance at INDIF+ (Note 4) ZINDIF+ 0 kΩ Input Impedance at INDIF(Note 4) ZINDIF- 0 kΩ ZOUT 26 kΩ ZOFFSET 26 kΩ Input Impedance at OUT (Note 4) Input Impedance at OFFSET (Note 4) POWER REQUIREMENTS Positive Power-Supply Voltage VDD 4.75 15.75 V Negative Power-Supply Voltage VSS -15.75 -4.75 V Positive Supply Current IDD Negative Supply Current ISS D1 = D0 = 0 10 D1 = D0 = 5V 36 80 0.01 10 µA µA TIMING REQUIREMENTS Switching Time (Note 5) tSWITCHING (Figure 3) 60 ns Note 1: Total error when configured as instrumentation amplifier. Assumes ideal op amps. Note 2: Each stage (input stage and output stage) is tested for accuracy separately and combined to give the total gain accuracy. The input stage is tested as follows: OUT1 = 10V, OUT2 = 0. Output stage is tested as follows OUT1 = 10V, OUT2 = 0 and OUT2 = 10V, OFFSET = 0. Note 3: Gain of 1 configuration is open circuit (infinite impedance). Note 4: Equivalent load at each pin is calculated according to instrumentation amplifier configuration and assumes ideal op amps. Note 5: See Timing Diagram. _______________________________________________________________________________________ 3 MAX5426 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VDD = +15V, VSS = -15V, TA = +25°C, unless otherwise noted.) MAX5426A GAIN ACCURACY vs. TEMPERATURE MAX5426A GAIN ACCURACY vs. POSITIVE SUPPLY VOLTAGE GAIN 4 GAIN 1 0 -0.005 -0.010 GAIN 2 GAIN 4 -0.004 -0.006 -0.008 35 50 65 80 TEMPERATURE (°C) 8.75 10.75 GAIN 4 -0.015 GAIN 8 MAX5426 toc03 -13 -0.010 -0.015 -0.030 -0.030 -9 -7 -5 POSITIVE SUPPLY CURRENT vs. TEMPERATURE GAIN 4 GAIN 8 -0.020 -11 NEGATIVE SUPPLY VOLTAGE (V) GAIN 2 GAIN 1 -0.025 GAIN 2 GAIN 8 -15 14.75 -0.005 -0.025 15 12 9 6 3 D1 = D0 = 0 20 40 60 4.75 80 6.75 8.75 10.75 12.75 POSITIVE SUPPLY VOLTAGE (V) NEGATIVE SUPPLY CURRENT vs. TEMPERATURE POSITIVE SUPPLY CURRENT vs. POSITIVE SUPPLY VOLTAGE -2 -4 -6 -8 30 20 15 10 5 20 35 50 65 20 40 80 60 80 0 -0.2 -0.4 -0.6 -0.8 -1.0 D1 = D0 = 0 5 TEMPERATURE (°C) 0 D1 = D0 = 5V -10 -40 -25 -10 -20 NEGATIVE SUPPLY CURRENT vs. NEGATIVE SUPPLY VOLTAGE 25 D1 = D0 = 0 -40 TEMPERATURE (°C) MAX5426 toc08 35 POSITIVE SUPPLY CURRENT (µA) 0 14.75 MAX5426 toc09 0 TEMPERATURE (°C) 0 NEGATIVE SUPPLY CURRENT (µA) -20 MAX5426 toc07 -40 4 12.75 0 GAIN ACCURACY (%) -0.005 -0.020 6.75 0.005 MAX5426 toc04 GAIN 2 GAIN 1 GAIN 1 -0.005 MAX5426B GAIN ACCURACY vs. POSITIVE SUPPLY VOLTAGE 0.005 -0.010 GAIN 4 POSITIVE SUPPLY VOLTAGE (V) MAX5426B GAIN ACCURACY vs. TEMPERATURE 0 0 -0.020 4.75 POSITIVE SUPPLY CURRENT (µA) 20 MAX5426 toc05 5 0.005 -0.015 -0.014 -40 -25 -10 0.010 -0.010 GAIN 8 -0.012 -0.020 GAIN ACCURACY (%) MAX5426 toc02 GAIN 2 -0.010 GAIN 8 -0.015 0 -0.002 0.015 MAX5426 toc06 0.005 GAIN 1 0.002 0.020 GAIN ACCURACY (%) 0.010 0.004 GAIN ACCURACY (%) GAIN ACCURACY (%) 0.015 MAX5426A GAIN ACCURACY vs. NEGATIVE SUPPLY VOLTAGE 0.006 MAX5426 toc01 0.020 NEGATIVE SUPPLY CURRENT (µA) MAX5426 Precision Resistor Network for Programmable Instrumentation Amplifiers -1.2 5 7 9 11 13 POSITIVE SUPPLY VOLTAGE (V) 15 -15 -13 -11 -9 -7 NEGATIVE SUPPLY VOLTAGE (V) _______________________________________________________________________________________ -5 Precision Resistor Network for Programmable Instrumentation Amplifiers PIN NAME 1 VDD Positive Power Supply. Bypass VDD to GND with a 0.1µF capacitor. 2 GND Ground 3 VSS Negative Power Supply. Bypass VSS to GND with a 0.1µF capacitor. FB2 First Stage Positive Input Terminal Resistor. Connect to the inverting terminal of the second input buffer (see Figure 1). 5 OUT2 First Stage Positive Output Terminal Resistor. Connect to the output terminal of the second input buffer. 6 OFFSET Second Stage Offset Terminal. Connect to a DC voltage to offset the output of the differential amplifier. 7 INDIF- Second Stage Negative Input Terminal Resistor. Connect to the inverting input terminal of the differential op amp. 8 INDIF+ Second Stage Positive Input Terminal Resistor. Connect to the noninverting input terminal of the differential op amp. 4 FUNCTION 9 OUT Second Stage Output Terminal, Final Output Terminal 10 OUT1 First Stage Negative Output Terminal of Resistor. Connect to the output terminal of the first input buffer. 11 FB1 First Stage Negative Input Terminal of Resistor. Connect to the inverting input terminal of the first input buffer. 12 CM Common-Mode Voltage. CM is the input common-mode voltage of the instrumentation amplifier. Typically varies ±1% of input common-mode voltage. 13, 14 D0, D1 Digital Inputs. See Table 1. Detailed Description Timing Diagram The MAX5426 is a precision resistor network with low temperature drift and high accuracy that performs the same function as a precision resistor array and CMOS switches. Operationally, this device consists of fixed resistors and digitally controlled variable resistors that provide differential gains of 1, 2, 4, and 8 (see Functional Diagram). The MAX5426 provides gains accurate to 0.025% (MAX5426A), 0.09% (MAX5426B) or 0.5% (MAX5426C). The MAX5426 is ideal for programmable instrumentation amplifiers. An offset pin is available to apply a DC offset voltage to the output of the differential amplifier. Pin CM is the common-mode input voltage and can be buffered and connected to the common-mode input of the instrumentation amplifier (usually the shield of the input cable to reduce the effects of cable capacitance and leakage). Figure 3 shows the timing diagram of MAX5426 for two cases. In case 1, the differential input changes are at OUT1 and OUT2, while the voltage settling is observed at FB1 and FB2. The settling time (tSETTLE) is defined as the time for the output voltage (from the change in the input) to reach (and stay) within 0.02% of its final value. In case 2, the differential inputs (OUT1 and OUT2) are at constant voltages, while D1 and D0 are varied (for example from 01 to 10) to make a change in the gain. No op amps are used in these cases. Table 1. Logic-Control Truth Table DIGITAL INPUTS D1 D0 GAIN 0 0 1 Digital Interface Operation 0 1 2 The MAX5426 features a simple two-bit parallel programming interface. D1 and D0 program the gain setting according to the Logic-Control Truth Table (see Table 1). The digital interface is CMOS/TTL logic compatible. 1 0 4 1 1 8 _______________________________________________________________________________________ 5 MAX5426 Pin Description MAX5426 Precision Resistor Network for Programmable Instrumentation Amplifiers MAX427 VIN- FB1 VDD OUT1 INDIF- D0 OUT D1 VOUT CM MAX5426 MAX427 OFFSET VSS GND FB2 OUT2 INDIF+ VIN+ MAX427 Figure 1. Programmable Instrumentation Amplifier Using MAX5426 Applications Information The MAX5426 is ideal for programmable instrumentation amplifier applications. The typical application circuit of Figure 1 uses the MAX5426 in classical instrumentation amplifier configurations. Two digital inputs set the gain to 1, 2, 4, or 8. Op Amp Selection Guidelines Selection of an op amp for instrumentation amplifier circuits depends on the accuracy requirements of the specific application. General guidelines are to choose an op amp with sufficient open-loop gain, low input-offset voltage, and a high common-mode rejection ratio. High open-loop gain is needed to increase the gain accuracy, while low input-offset voltage and low inputoffset current help meet gain and offset requirements. Other parameters such as low input capacitance, low input bias current, high input common-mode range, and low noise often need to be considered for a wide input voltage range stability and AC considerations. The MAX427 is an excellent choice to use with the MAX5426. 6 Stereo Audio-Taper Attenuator Figure 2 shows the application of the MAX5426 as a dual attenuator that can be used in stereo audio systems. Power Supplies and Bypassing The MAX5426 operates from dual ±5V to ±15V supplies. In many applications the MAX5426 does not require bypassing. If power-supply noise is excessive, bypass VDD and VSS with 0.1µF ceramic capacitors to GND. Layout Concerns For best performance, reduce parasitic board capacitance by minimizing the circuit board trace from amplifier outputs to inverting inputs. Also choose op amps with low input capacitance. _______________________________________________________________________________________ Precision Resistor Network for Programmable Instrumentation Amplifiers FB1 MAX5426 TO RIGHT CHANNEL AMPLIFIER RIGHT CHANNEL INDIF- OUT1 VDD OUT CM D1 D0 OFFSET VSS FB2 GND TO LEFT CHANNEL AMPLIFIER OUT2 INDIF+ LEFT CHANNEL Figure 2. Stereo Audio-Taper Attenuator OUT1 OUT1 tSETTLE tSWITCHING tSETTLE FB1 FB1 FB2 FB2 OUT2 OUT2 D1, D0 D1, D0 CASE 1: DIFFERENTIAL INPUT IS CHANGED, WHILE D1, D0 IS FIXED. NOTE: SEE TIMING DIAGRAM SECTION CASE 2: DIFFERENTIAL INPUT IS FIXED, WHILE D1, D0 IS CHANGED FROM 00 TO 01. Figure 3. Timing Diagram _______________________________________________________________________________________ 7 Precision Resistor Network for Programmable Instrumentation Amplifiers MAX5426 Functional Diagram VDD FB1 OUT1 INDIF- D1 D0 OUT CM MAX5426 OFFSET GND VSS FB2 Pin Configuration OUT2 INDIF+ Chip Information TRANSISTOR COUNT: 126 PROCESS TECHNOLOGY: BICMOS TOP VIEW VDD 1 14 D1 GND 2 13 D0 VSS 3 12 CM FB2 4 OUT2 5 8 MAX5426 11 FB1 10 OUT1 OFFSET 6 9 OUT INDIF- 7 8 INDIF+ _______________________________________________________________________________________ Precision Resistor Network for Programmable Instrumentation Amplifiers TSSOP,NO PADS.EPS Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX5426 Package Information