Not Recommended for New Designs The MAX495 was manufactured for Maxim by an outside wafer foundry using a process that is no longer available. It is not recommended for new designs. A Maxim replacement or an industry second-source may be available. The data sheet remains available for existing users. The other parts on the following data sheet are not affected. For further information, please see the QuickView data sheet for this part or contact technical support for assistance. 19-0265; Rev 2; 9/96 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps The dual MAX492, quad MAX494, and single MAX495 operational amplifiers combine excellent DC accuracy with rail-to-rail operation at the input and output. Since the common-mode voltage extends from VCC to VEE, the devices can operate from either a single supply (+2.7V to +6V) or split supplies (1.35V to 3V). Each op amp requires less than 150A supply current. Even with this low current, the op amps are capable of driving a 1k load, and the input referred voltage noise is only 25nV/Hz. In addition, these op amps can drive loads in excess of 1nF. The precision performance of the MAX492/MAX494/ MAX495, combined with their wide input and output dynamic range, low-voltage single-supply operation, and very low supply current, makes them an ideal choice for battery-operated equipment and other low-voltage applications. The MAX492/MAX494/MAX495 are available in DIP and SO packages in the industry-standard op-amp pin configurations. The MAX495 is also available in the smallest 8-pin SO: the MAX package. ________________________Applications Portable Equipment Battery-Powered Instruments Data Acquisition Signal Conditioning Low-Voltage Applications ____________________________Features Low-Voltage Single-Supply Operation (+2.7V to +6V) Rail-to-Rail Input Common-Mode Voltage Range Rail-to-Rail Output Swing 500kHz Gain-Bandwidth Product Unity-Gain Stable 150A Max Quiescent Current per Op Amp No Phase Reversal for Overdriven Inputs 200V Offset Voltage High Voltage Gain (108dB) High CMRR (90dB) and PSRR (110dB) Drives 1k Load Drives Large Capacitive Loads MAX495 Available in MAX Package--8-Pin SO ______________Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX492CPA 0C to +70C 8 Plastic DIP MAX492CSA MAX492C/D MAX492EPA MAX492ESA MAX492MJA 0C to +70C 0C to +70C -40C to +85C -40C to +85C -55C to +125C 8 SO Dice* 8 Plastic DIP 8 SO 8 CERDIP Ordering Information continued at end of data sheet. *Dice are specified at TA = +25C, DC parameters only. __________Typical Operating Circuit _________________Pin Configurations TOP VIEW +5V 1 VDD 10k 2 MAX187 (ADC) 7 6 3 ANALOG INPUT MAX495 2 DOUT 6 8 SCLK 7 CS AIN 4 3 SHDN 4 REF 10k OUT1 1 8 VCC IN1- 2 7 OUT2 IN1+ 3 6 IN2- 5 IN2+ 8 N.C. 7 VCC IN1+ 3 6 OUT VEE 4 5 NULL VEE 4 MAX492 DIP/SO SERIAL INTERFACE NULL 1 4.096V GND 5 IN1- 2 MAX495 DIP/SO/MAX INPUT SIGNAL CONDITIONING FOR LOW-VOLTAGE ADC Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MAX492/MAX494/MAX495 _______________General Description MAX492/MAX494/MAX495 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC to VEE) ....................................................7V Common-Mode Input Voltage..........(VCC + 0.3V) to (VEE - 0.3V) Differential Input Voltage .........................................(VCC - VEE) Input Current (IN+, IN-, NULL1, NULL2) ..........................10mA Output Short-Circuit Duration ....................Indefinite short circuit to either supply Voltage Applied to NULL Pins ....................................VCC to VEE Continuous Power Dissipation (TA = +70C) 8-Pin Plastic DIP (derate 9.09mW/C above +70C) ....727mW 8-Pin SO (derate 5.88mW/C above +70C).................471mW 8-Pin CERDIP (derate 8.00mW/C above +70C).........640mW 8-Pin MAX (derate 4.1mW/C above +70C) ..............330mW 14-Pin Plastic DIP (derate 10.00mW/C above +70C)...800mW 14-Pin SO (derate 8.33mW/C above +70C)...............667mW 14-Pin CERDIP (derate 9.09mW/C above +70C).......727mW Operating Temperature Ranges MAX49_C_ _ ........................................................0C to +70C MAX49_E_ _......................................................-40C to +85C MAX49_M_ _ ...................................................-55C to +125C Junction Temperatures MAX49_C_ _/E_ _..........................................................+150C MAX49_M_ _ .................................................................+175C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+300C 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. DC ELECTRICAL CHARACTERISTICS (VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA = +25C, unless otherwise noted.) PARAMETER CONDITIONS TYP MAX UNITS 200 500 V VCM = VEE to VCC 25 60 nA VCM = VEE to VCC 0.5 6 Input Offset Voltage VCM = VEE to VCC Input Bias Current Input Offset Current Differential Input Resistance Common-Mode Input Voltage Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio Large-Signal Voltage Gain (Note 1) Output Voltage Swing (Note 1) MIN 2 VEE - 0.25 V 74 90 dB VCC = 2.7V to 6V VCC = 2.7V, RL = 100k, VOUT = 0.25V to 2.45V dB 88 110 Sourcing 90 104 Sinking 90 102 VCC = 2.7V, RL = 1k, VOUT = 0.5V to 2.2V Sourcing 94 105 Sinking 78 90 VCC = 5.0V, RL = 100k, VOUT = 0.25V to 4.75V Sourcing 98 108 Sinking 92 100 VCC = 5.0V, RL = 1k, VOUT = 0.5V to 4.5V Sourcing 98 110 86 98 RL = 100k Sinking VOH VOL VOH dB VCC - 0.075 VCC - 0.04 VEE + 0.04 VEE + 0.075 VCC - 0.20 VOL VCC - 0.15 30 Operating Supply Voltage Range 2.7 VCM = VOUT = VCC / 2 V VEE + 0.15 VEE + 0.20 Output Short-Circuit Current 2 VCC + 0.25 (VEE - 0.25V) VCM (VCC + 0.25V) RL = 1k Supply Current (per amplifier) nA M mA 6.0 VCC = 2.7V 135 150 VCC = 5V 150 170 _______________________________________________________________________________________ V A Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps (VCC = 2.7V to 6V, VEE = GND, TA = +25C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS Gain-Bandwidth Product RL = 100k, CL = 100pF 500 kHz Phase Margin RL = 100k, CL = 100pF 60 degrees Gain Margin RL = 100k, CL = 100pF 10 dB Total Harmonic Distortion RL = 10k, CL = 15pF, VOUT = 2Vp-p, AV = +1, f = 1kHz 0.003 % Slew Rate RL = 100k, CL = 15pF 0.20 V/s Time To 0.1%, 2V step 12 s Turn-On Time VCC = 0V to 3V step, VIN = VCC / 2, AV = +1 5 s Input Noise-Voltage Density f = 1kHz 25 nV/Hz Input Noise-Current Density f = 1kHz 0.1 pA/Hz Amp-Amp Isolation f = 1kHz 125 dB DC ELECTRICAL CHARACTERISTICS (VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA = 0C to +70C, unless otherwise noted.) PARAMETER Input Offset Voltage CONDITIONS MIN TYP VCM = VEE to VCC MAX 650 Input Offset Voltage Tempco 2 UNITS V V/C Input Bias Current VCM = VEE to VCC 75 nA Input Offset Current Common-Mode Input Voltage Range Common-Mode Rejection Ratio VCM = VEE to VCC 6 nA (VEE - 0.20) VCM (VCC + 0.20) 72 dB Power-Supply Rejection Ratio VCC = 2.7V to 6V 86 dB Large-Signal Voltage Gain (Note 1) Output Voltage Swing (Note 1) VEE - 0.20 VCC = 2.7V, RL = 100k, VOUT = 0.25V to 2.45V Sourcing 88 Sinking 84 VCC = 2.7V, RL = 1k, VOUT = 0.5V to 2.2V Sourcing 92 Sinking 76 VCC = 5.0V, RL = 100k, VOUT = 0.25V to 4.75V Sourcing 92 Sinking 88 VCC = 5.0V, RL = 1k, VOUT = 0.5V to 4.5V Sourcing 96 RL = 100k RL = 1k Sinking VOH Supply Current (per amplifier) VEE + 0.075 VCC - 0.20 V VEE + 0.20 2.7 VCM = VOUT = VCC / 2 dB 82 VOL Operating Supply Voltage Range V VCC - 0.075 VOL VOH VCC + 0.20 6.0 VCC = 2.7V 175 VCC = 5V 190 V A _______________________________________________________________________________________ 3 MAX492/MAX494/MAX495 AC ELECTRICAL CHARACTERISTICS MAX492/MAX494/MAX495 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps DC ELECTRICAL CHARACTERISTICS (VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA = -40C to +85C, unless otherwise noted.) PARAMETER Input Offset Voltage CONDITIONS MIN MAX VCM = VEE to VCC 950 Input Offset Voltage Tempco 2 UNITS V V/C Input Bias Current VCM = VEE to VCC 100 nA Input Offset Current Common-Mode Input Voltage Range Common-Mode Rejection Ratio VCM = VEE to VCC 8 nA (VEE - 0.15) VCM (VCC + 0.15) 68 dB Power-Supply Rejection Ratio VCC = 2.7V to 6V, VCM = 0V 84 dB Large-Signal Voltage Gain (Note 1) Output Voltage Swing (Note 1) VEE - 0.15 VCC = 2.7V, RL = 100k, VOUT = 0.25V to 2.45V Sourcing 86 Sinking 84 VCC = 2.7V, RL = 1k, VOUT = 0.5V to 2.2V Sourcing 92 Sinking 76 VCC = 5.0V, RL = 100k, VOUT = 0.25V to 4.75V Sourcing 92 Sinking 86 VCC = 5.0V, RL = 1k, VOUT = 0.5V to 4.5V Sourcing 96 Sinking 80 RL = 100k RL = 1k VOH VOH Supply Current (per amplifier) VCC + 0.15 dB VEE + 0.075 VCC - 0.20 VOL V VEE + 0.20 2.7 VCM = VOUT = VCC / 2 V VCC - 0.075 VOL Operating Supply-Voltage Range 4 TYP 6.0 VCC = 2.7V 185 VCC = 5V 200 _______________________________________________________________________________________ V A Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps MAX492/MAX494/MAX495 DC ELECTRICAL CHARACTERISTICS (VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA = -55C to +125C, unless otherwise noted.) PARAMETER Input Offset Voltage CONDITIONS MIN TYP VCM = VEE to VCC Input Offset Voltage Tempco MAX UNITS 1.2 mV 2 V/C Input Bias Current VCM = VEE to VCC 200 nA Input Offset Current VCM = VEE to VCC 10 nA Common-Mode Input Voltage Range VEE - 0.05 VCC + 0.05 V Common-Mode Rejection Ratio (VEE - 0.05V) VCM (VCC + 0.05V) 66 dB Power-Supply Rejection Ratio VCC = 2.7V to 6V 80 dB Large-Signal Voltage Gain (Note 1) Output Voltage Swing (Note 1) VCC = 2.7V, RL = 100k, VOUT = 0.25V to 2.45V Sourcing 82 Sinking 80 VCC = 2.7V, RL = 1k, VOUT = 0.5V to 2.2V Sourcing 90 Sinking 72 VCC = 5.0V, RL = 100k, VOUT = 0.25V to 4.75V Sourcing 86 Sinking 82 VCC = 5.0V, RL = 1k, VOUT = 0.5V to 4.5V Sourcing 94 RL = 100k RL = 1k Sinking VOH VEE + 0.075 VCC - 0.250 VOL Operating Supply-Voltage Range Supply Current (per amplifier) 76 VCC - 0.075 VOL VOH V VEE + 0.250 2.7 VCM = VOUT = VCC / 2 dB 6.0 VCC = 2.7V 200 VCC = 5V 225 V A Note 1: RL to VEE for sourcing and VOH tests; RL to VCC for sinking and VOL tests. _______________________________________________________________________________________ 5 __________________________________________Typical Operating Characteristics (TA = +25C, VCC = 5V, VEE = 0V, unless otherwise noted.) GAIN AND PHASE vs. FREQUENCY MAX492-01 80 180 60 80 120 140 60 120 GAIN -60 0 PHASE PSRR (dB) 0 20 PHASE (DEG) GAIN (dB) 0 PHASE 100 60 40 PHASE (DEG) 60 40 GAIN (dB) 180 120 GAIN 20 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY MAX492-02 MAX492-03 GAIN AND PHASE vs. FREQUENCY -60 0 VCC 80 60 40 VEE 20 FREQUENCY (kHz) 10 1 100 MAX492-04 160 OFFSET VOLTAGE (V) 120 100 80 60 40 VCM = 0V 140 20 120 110 80 60 100 1000 10,000 80 70 INPUT BIAS CURRENT (nA) 100 VCC = 6V 5 0 -5 -10 -15 -20 25 -50 4 VCM (V) 5 6 7 VCM = 0 -75 -125 3 VCC = 2.7V -25 -30 2 VCM = VCC 0 -100 1 SUPPLY CURRENT PER AMPLIFIER vs. TEMPERATURE 50 -25 0 VCC = 6V 75 VCC = 6V -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) 125 MAX492-07 VCC = 2.7V VCM = -0.4V TO +5.4V -60 -40 -20 0 INPUT BIAS CURRENT vs. TEMPERATURE 20 10 20 40 60 80 100 120 140 TEMPERATURE (C) INPUT BIAS CURRENT vs. COMMON-MODE VOLTAGE VCM = -0.2V TO +5.2V VCM = -0.3V TO +5.3V 60 -60 -40 -20 0 FREQUENCY (kHz) 15 90 40 0 10 1 VCM = 0V TO +5V VCM = -01V TO +5.1V 100 100 20 40 60 80 100 120 140 TEMPERATURE (C) 220 SUPPLY CURRENT PER OP AMP (A) 0.1 1000 120 MAX492-08 0 0.01 100 10 COMMON-MODE REJECTION RATIO vs. TEMPERATURE 20 VIN = 2.5V 1 FREQUENCY (kHz) OFFSET VOLTAGE vs. TEMPERATURE 140 CHANNEL SEPARATION (dB) 0.1 VIN = 2.5V -20 0.1 0.01 FREQUENCY (kHz) CHANNEL SEPARATION vs. FREQUENCY 6 0 -180 1000 10,000 MAX492-06 100 -40 0.01 -120 CMRR (dB) 10 -180 1000 10,000 CL = 470pF AV = +1000 RL = MAX492-05 AV = +1000 NO LOAD -40 0.01 0.1 1 -20 200 MAX492-09 -120 -20 INPUT BIAS CURRENT (nA) MAX492/MAX494/MAX495 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps VOUT = VCM = VCC/2 180 160 VCC = 5V 140 VCC = 2.7V 120 100 80 60 40 20 0 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) _______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE 110 100 RL = 100k RL = 1k 80 70 90 RL = 100k RL = 10k RL = 1k 80 70 VCC = +6V RL TO VEE 60 VCC = +2.7V RL TO VEE 60 50 500 600 100 LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE GAIN (dB) 80 VCC = +6V RL TO VCC 500 600 140 VCC = 2.7V, RL = 1k 100 80 VCC = 6V, RL = 100k 40 20 VCC = 2.7V, RL = 100k 0 0 20 40 60 80 100 120 140 TEMPERATURE (C) 95 RL TO VEE 90 80 100 200 300 400 VOUT (mV) 500 -60 -40 -20 0 600 180 RL TO VEE 160 VCC = 6V, RL = 1k 140 OUTPUT IMPEDANCE vs. FREQUENCY VCC = 2.7V, RL = 1k 120 100 80 60 40 20 40 60 80 100 120 140 TEMPERATURE (C) VCC = 6V, RL = 100k VCC = 2.7V, RL = 100k 1000 VCM = VOUT = 2.5V 100 10 1 20 0 -60 -40 -20 105 85 200 (VCC - VOUT) (mV) VOUT MIN (mV) 160 VCC = +6V 100 MAXIMUM OUTPUT VOLTAGE vs. TEMPERATURE VCC = 6V, RL = 1k 120 RL TO VCC 110 VCC = +2.7V VCC = +2.7V RL TO VCC 0 MAX492-16 RL TO VCC RL = 100k, 0.3V < VOUT < (VCC - 0.3V) 115 OUTPUT IMPEDANCE () 300 400 VOUT (mV) 220 60 RL = 1k RL = 10k 60 MINIMUM OUTPUT VOLTAGE vs. TEMPERATURE 180 120 50 200 20 40 60 80 100 120 140 LARGE-SIGNAL GAIN vs. TEMPERATURE 90 70 50 200 -60 -40 -20 0 MAX492-17 GAIN (dB) 70 100 RL TO VEE TEMPERATURE (C) RL = 100k RL = 1k RL = 10k 0 VCC = +6V 90 600 100 90 60 500 RL = 1M 110 RL = 100k 80 400 200 300 VCC - VOUT (mV) 120 MAX492-13 RL = 1M 100 VCC = +2.7V 95 LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE 120 110 100 80 0 LARGE-SIGNAL GAIN (dB) 400 200 300 VCC - VOUT (mV) MAX492-14 100 105 85 50 0 RL TO VCC 110 MAX492-15 90 GAIN (dB) RL = 1M RL = 1k, 0.5V < VOUT < (VCC - 0.5V) 115 MAX492-18 100 RL = 1M LARGE-SIGNAL GAIN (dB) 110 120 MAX492-11 RL = 10k GAIN (dB) 120 MAX492-10 120 LARGE-SIGNAL GAIN vs. TEMPERATURE MAX492-12 LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE 0.1 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz) _______________________________________________________________________________________ 7 MAX492/MAX494/MAX495 ____________________________Typical Operating Characteristics (continued) (TA = +25C, VCC = 5V, VEE = 0V, unless otherwise noted.) ____________________________Typical Operating Characteristics (continued) (TA = +25C, VCC = 5V, VEE = 0V, unless otherwise noted.) CURRENT-NOISE DENSITY vs. FREQUENCY VOLTAGE-NOISE DENSITY vs. FREQUENCY CURRENT-NOISE DENSITY (pA/Hz) 10 INPUT REFERRED MAX492-20 5.0 MAX492-19 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 INPUT REFERRED 0 1 0.01 1 0.1 0.01 10 10 TOTAL HARMONIC DISTORTION + NOISE vs. PEAK-TO-PEAK SIGNAL AMPLITUDE TOTAL HARMONIC DISTORTION + NOISE vs. FREQUENCY 0.1 MAX492-21 0.1 THD + NOISE (%) AV = +1 2VP-P SIGNAL 80kHz LOWPASS FILTER 0.01 1 0.1 FREQUENCY (kHz) FREQUENCY (kHz) RL = 10k TO GND AV = +1 1kHz SINE 22kHz FILTER RL TO GND MAX492-22 VOLTAGE-NOISE DENSITY (nV/Hz) 100 THD + NOISE (%) MAX492/MAX494/MAX495 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps RL = 1k RL = 2k 0.01 RL = 100k RL = 10k NO LOAD 0.001 0.001 10 1000 100 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 10,000 PEAK-TO-PEAK SIGNAL AMPLITUDE (V) FREQUENCY (Hz) SMALL-SIGNAL TRANSIENT RESPONSE SMALL-SIGNAL TRANSIENT RESPONSE 2s/div VCC = +5V, AV = +1, RL = 10k 8 VIN 50mV/div VIN 50mV/div VOUT 50mV/div VOUT 50mV/div 2s/div VCC = +5V, AV = -1, RL = 10k _______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps LARGE-SIGNAL TRANSIENT RESPONSE LARGE-SIGNAL TRANSIENT RESPONSE VIN 2V/div VIN 2V/div VOUT 2V/div VOUT 2V/div 50s/div 50s/div VCC = +5V, AV = +1, RL = 10k VCC = +5V, AV = -1, RL = 10k ______________________________________________________________Pin Description PIN MAX492 MAX494 MAX495 NAME FUNCTION 1 1 -- OUT1 Amplifier 1 Output -- -- 1, 5 NULL Offset Null Input. Connect to a 10k potentiometer for offset-voltage trimming. Connect wiper to VEE (Figure 3). -- -- 2 IN- Inverting Input 2 2 -- IN1- Amplifier 1 Inverting Input -- -- 3 IN+ Noninverting Input 3 3 -- IN1+ Amplifier 1 Noninverting Input 4 11 4 VEE Negative Power-Supply Pin. Connect to ground or a negative voltage. 5 5 -- IN2+ Amplifier 2 Noninverting Input -- -- 6 OUT Amplifier Output 6 6 -- IN2- Amplifier 2 Inverting Input 7 7 -- OUT2 8 4 7 VCC -- 8 -- OUT3 -- 9 -- IN3- Amplifier 3 Inverting Input -- 10 -- IN3+ Amplifier 3 Noninverting Input -- 12 -- IN4+ Amplifier 4 Noninverting Input -- 13 -- IN4- Amplifier 4 Inverting Input -- 14 -- OUT4 -- -- 8 N.C. Amplifier 2 Output Positive Power-Supply Pin. Connect to (+) terminal of power supply. Amplifier 3 Output Amplifier 4 Output No Connect. Not internally connected. _______________________________________________________________________________________ 9 MAX492/MAX494/MAX495 ____________________________Typical Operating Characteristics (continued) (TA = +25C, VCC = 5V, VEE = 0V, unless otherwise noted.) MAX492/MAX494/MAX495 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps __________Applications Information The dual MAX492, quad MAX494, and single MAX495 op amps combine excellent DC accuracy with rail-torail operation at both input and output. With their precision performance, wide dynamic range at low supply voltages, and very low supply current, these op amps are ideal for battery-operated equipment and other lowvoltage applications. Rail-to-Rail Inputs and Outputs The MAX492/MAX494/MAX495's input common-mode range extends 0.25V beyond the positive and negative supply rails, with excellent common-mode rejection. Beyond the specified common-mode range, the outputs are guaranteed not to undergo phase reversal or latchup. Therefore, the MAX492/MAX494/MAX495 can be used in applications with common-mode signals at or even beyond the supplies, without the problems associated with typical op amps. The MAX492/MAX494/MAX495's output voltage swings to within 50mV of the supplies with a 100k load. This rail-to-rail swing at the input and output substantially increases the dynamic range, especially in low supplyvoltage applications. Figure 1 shows the input and output waveforms for the MAX492, configured as a unity-gain noninverting buffer operating from a single +3V supply. The input signal is 3.0Vp-p, 1kHz sinusoid centered at +1.5V. The output amplitude is approximately 2.95Vp-p. Input Offset Voltage Rail-to-rail common-mode swing at the input is obtained by two complementary input stages in parallel, which feed a folded cascaded stage. The PNP stage is active for input voltages close to the negative rail, and the NPN stage is active for input voltages close to the positive rail. The offsets of the two pairs are trimmed; however, there is some small residual mismatch between them. This mismatch results in a two-level input offset characteristic, with a transition region between the levels occurring at a common-mode voltage of approximately 1.3V. Unlike other rail-to-rail op amps, the transition region has been widened to approximately 600mV in order to minimize the slight degradation in CMRR caused by this mismatch. To adjust the MAX495's input offset voltage (500V max at +25C), connect a 10k trim potentiometer between the two NULL pins (pins 1 and 5), with the wiper connected to VEE (pin 4) (Figure 2). The trim range of this circuit is 6mV. External offset adjustment is not available for the dual MAX492 or quad MAX494. The input bias currents of the MAX492/MAX494/MAX495 are typically less than 50nA. The bias current flows into the device when the NPN input stage is active, and it flows out when the PNP input stage is active. To reduce the offset error caused by input bias current flowing through external source resistances, match the effective resistance seen at each input. Connect resistor R3 between the noninverting input and ground when using 10k VIN 1 NULL MAX495 VOUT 4 Figure 1. Rail-to-Rail Input and Output (Voltage Follower Circuit, VCC = +3V, VEE = 0V) 10 VEE NULL 5 Figure 2. Offset Null Circuit ______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps (Figure 4). The diodes limit the differential voltage applied to the amplifiers' internal circuitry to no more than VF, where VF is the diodes' forward-voltage drop (about 0.7V at +25C). Input bias current for the ICs (25nA typical) is specified for the small differential input voltages. For large differential input voltages (exceeding VF), this protection circuitry increases the input current at IN+ and IN-: Input Stage Protection Circuitry The MAX492/MAX494/MAX495 include internal protection circuitry that prevents damage to the precision input stage from large differential input voltages. This protection circuitry consists of back-to-back diodes between IN+ and IN- with two 1.7k resistors in series (VIN+ - VIN- ) - VF Input Current = ---------------------- 2 x 1.7k For comparator applications requiring large differential voltages (greater than VF), you can limit the input current that flows through the diodes with external resistors R2 MAX492 MAX494 MAX495 TO INTERNAL CIRCUITRY 1.7k IN+ R1 VIN VOUT MAX49_ R3 R3 = R2 II R1 IN- TO INTERNAL CIRCUITRY 1.7k Figure 3a. Reducing Offset Error Due to Bias Current: Inverting Configuration Figure 4. Input Stage Protection Circuitry MAX492-FG 04 10,000 R3 VIN VOUT MAX49_ R2 R3 = R2 II R1 R1 CAPACITIVE LOAD (pF) UNSTABLE REGION 1000 VCC = +5V VOUT = VCC/2 RL TO VEE AV = +1 100 1 10 100 RESISTIVE LOAD (k) Figure 3b. Reducing Offset Error Due to Bias Current: Figure 5. Capacitive-Load Stable Region Sourcing Current Noninverting Configuration ______________________________________________________________________________________ 11 MAX492/MAX494/MAX495 the op amp in an inverting configuration (Figure 3a); connect resistor R3 between the noninverting input and the input signal when using the op amp in a noninverting configuration (Figure 3b). Select R3 to equal the parallel combination of R1 and R2. High source resistances will degrade noise performance, due to the thermal noise of the resistor and the input current noise (which is multiplied by the source resistance). MAX492/MAX494/MAX495 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps in series with IN-, IN+, or both. Series resistors are not recommended for amplifier applications, as they may increase input offsets and decrease amplifier bandwidth. Output Loading and Stability Even with their low quiescent current of less than 150A per op amp, the MAX492/MAX494/MAX495 are well suited for driving loads up to 1k while maintaining DC accuracy. Stability while driving heavy capacitive loads is another key advantage over comparable CMOS railto-rail op amps. VIN 50mV/div VIN 50mV/div VOUT 50mV/div VOUT 50mV/div 10s/div 10s/div Figure 6. MAX492 Voltage Follower with 1000pF Load (RL = ) Figure 7b. MAX492 Voltage Follower with 500pF Load-- RL = 20k VIN 50mV/div VIN 50mV/div VOUT 50mV/div VOUT 50mV/div 10s/div Figure 7a. MAX492 Voltage Follower with 500pF Load-- RL = 5k 12 In op amp circuits, driving large capacitive loads increases the likelihood of oscillation. This is especially true for circuits with high loop gains, such as a unitygain voltage follower. The output impedance and a capacitive load form an RC network that adds a pole to the loop response and induces phase lag. If the pole frequency is low enough--as when driving a large capacitive load--the circuit phase margin is degraded, leading to either an under-damped pulse response or oscillation. 10s/div Figure 7c. MAX492 Voltage Follower with 500pF Load-- RL = ______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps To increase stability while driving large capacitive loads, connect a pull-up resistor at the output to decrease the current that the amplifier must source. If the amplifier is made to sink current rather than source, stability is further increased. Frequency stability can be improved by adding an output isolation resistor (RS) to the voltage-follower circuit (Figure 8). This resistor improves the phase margin of the circuit by isolating the load capacitor from the op amp's output. Figure 9a shows the MAX492 driving 10,000pF (RL 100k), while Figure 9b adds a 47 isolation resistor. VIN 50mV/div RS VOUT MAX49_ CL VIN VOUT 50mV/div 10s/div Figure 9b. Driving a 10,000pF Capacitive Load with a 47 Isolation Resistor Figure 8. Capacitive-Load Driving Circuit +5V VCC VIN 50mV/div 2 7 1k 6 MAX495 3 VOUT 50mV/div VOUT 4 1k 10s/div Figure 9a. Driving a 10,000pF Capacitive Load Figure 10. Power-Up Test Configuration ______________________________________________________________________________________ 13 MAX492/MAX494/MAX495 The MAX492/MAX494/MAX495 can drive capacitive loads in excess of 1000pF under certain conditions (Figure 5). When driving capacitive loads, the greatest potential for instability occurs when the op amp is sourcing approximately 100A. Even in this case, stability is maintained with up to 400pF of output capacitance. If the output sources either more or less current, stability is increased. These devices perform well with a 1000pF pure capacitive load (Figure 6). Figure 7 shows the performance with a 500pF load in parallel with various load resistors. MAX492/MAX494/MAX495 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps VCC 2V/div VCC 1V/div VOUT 500mV/div 5s/div Figure 11a. Power-Up Settling Time (VCC = +3V) Because the MAX492/MAX494/MAX495 have excellent stability, no isolation resistor is required, except in the most demanding applications. This is beneficial because an isolation resistor would degrade the lowfrequency performance of the circuit. Power-Up Settling Time The MAX492/MAX494/MAX495 have a typical supply current of 150A per op amp. Although supply current is already low, it is sometimes desirable to reduce it further by powering down the op amp and associated ICs for periods of time. For example, when using a MAX494 to buffer the inputs to a multi-channel analog-to-digital converter (ADC), much of the circuitry could be powered down between data samples to increase battery life. If samples are taken infrequently, the op amps, along with the ADC, may be powered down most of the time. When power is reapplied to the MAX492/MAX494/ MAX495, it takes some time for the voltages on the supply pin and the output pin of the op amp to settle. Supply settling time depends on the supply voltage, the value of the bypass capacitor, the output impedance of the incoming supply, and any lead resistance or inductance between components. Op amp settling time depends primarily on the output voltage and is slew-rate limited. With the noninverting input to a voltage follower held at mid-supply (Figure 10), when the supply steps from 0V to VCC, the output settles in approximately 4s for V CC = +3V (Figure 11a) or 10s for V CC = +5V (Figure 11b). 14 VOUT 1V/div 5s/div Figure 11b. Power-Up Settling Time (VCC = +5V) Power Supplies and Layout The MAX492/MAX494/MAX495 operate from a single 2.7V to 6V power supply, or from dual supplies of 1.35V to 3V. For single-supply operation, bypass the power supply with a 1F capacitor in parallel with a 0.1F ceramic capacitor. If operating from dual supplies, bypass each supply to ground. Good layout improves performance by decreasing the amount of stray capacitance at the op amp's inputs and output. To decrease stray capacitance, minimize both trace lengths and resistor leads and place external components close to the op amp's pins. Rail-to-Rail Buffers The Typical Operating Circuit shows a MAX495 gain-oftwo buffer driving the analog input to a MAX187 12-bit ADC. Both devices run from a single 5V supply, and the converter's internal reference is 4.096V. The MAX495's typical input offset voltage is 200V. This results in an error at the ADC input of 400V, or less than half of one least significant bit (LSB). Without offset trimming, the op amp contributes negligible error to the conversion result. ______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps PART TEMP. RANGE _________________Chip Topographies MAX492 PIN-PACKAGE MAX494CPD 0C to +70C 14 Plastic DIP MAX494CSD MAX494EPD MAX494ESD MAX494MJD MAX495CPA 0C to +70C -40C to +85C -40C to +85C -55C to +125C 0C to +70C 14 SO 14 Plastic DIP 14 SO 14 CERDIP 8 Plastic DIP MAX495CSA MAX495CUA MAX495C/D MAX495EPA MAX495ESA MAX495MJA 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -55C to +125C 8 SO 8 MAX Dice* 8 Plastic DIP 8 SO 8 CERDIP IN1+ IN1- V CC OUT1 0.068" (1.728mm) V EE V CC V CC OUT2 * Dice are specified at TA = +25C, DC parameters only. IN2+ IN2- 0.069" (1.752mm) ____Pin Configurations (continued) MAX495 NULL1 TOP VIEW INOUT1 1 14 OUT4 IN1- 2 13 IN4- IN1+ 3 12 IN4+ VCC 4 MAX494 11 VEE IN2+ 5 10 IN3+ IN2- 6 9 IN3- OUT2 7 8 OUT3 V CC 0.056" (1.422mm) OUT IN+ V EE DIP/SO NULL2 0.055" (1.397mm) TRANSISTOR COUNT: 134 (single MAX495) 268 (dual MAX492) 536 (quad MAX494) SUBSTRATE CONNECTED TO VEE ______________________________________________________________________________________ 15 MAX492/MAX494/MAX495 _Ordering Information (continued) MAX492/MAX494/MAX495 Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps ________________________________________________________Package Information DIM C A 0.101mm 0.004 in e B A1 L A A1 B C D E e H L INCHES MAX MIN 0.044 0.036 0.008 0.004 0.014 0.010 0.007 0.005 0.120 0.116 0.120 0.116 0.0256 0.198 0.188 0.026 0.016 6 0 MILLIMETERS MIN MAX 0.91 1.11 0.10 0.20 0.25 0.36 0.13 0.18 2.95 3.05 2.95 3.05 0.65 4.78 5.03 0.41 0.66 0 6 21-0036D E H 8-PIN MAX MICROMAX SMALL-OUTLINE PACKAGE D DIM D 0-8 A 0.101mm 0.004in. e B A1 E C L Narrow SO SMALL-OUTLINE PACKAGE (0.150 in.) H A A1 B C E e H L INCHES MAX MIN 0.069 0.053 0.010 0.004 0.019 0.014 0.010 0.007 0.157 0.150 0.050 0.244 0.228 0.050 0.016 DIM PINS D D D 8 14 16 MILLIMETERS MIN MAX 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 3.80 4.00 1.27 5.80 6.20 0.40 1.27 INCHES MILLIMETERS MIN MAX MIN MAX 0.189 0.197 4.80 5.00 0.337 0.344 8.55 8.75 0.386 0.394 9.80 10.00 21-0041A 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. 16 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.