19-2272; Rev 0; 1/02 Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps Features ♦ Low-Voltage, Single-Supply Operation (2.7V to 6V) ________________________Applications ♦ Beyond-the-Rails™ Inputs ♦ No Phase Reversal for Overdriven Inputs ♦ 30µV Offset Voltage ♦ Rail-to-Rail Output Swing with 1kΩ Load ♦ Unity-Gain Stable with 2000pF Load ♦ 165µA (max) Quiescent Current Per Op Amp ♦ 500kHz Gain-Bandwidth Product ♦ High Voltage Gain (115dB) ♦ High Common-Mode Rejection Ratio (90dB) and Power-Supply Rejection Ratio (100dB) ♦ Temperature Range (-40°C to +125°C) Ordering Information PART TEMP RANGE PIN-PACKAGE MAX4091AUK-T -40°C to +125°C 5 SOT23-5 Portable Equipment MAX4091ASA -40°C to +125°C 8 SO Battery-Powered Instruments MAX4091AUA -40°C to +125°C 8 µMAX Data Acquisition and Control MAX4092ASA -40°C to +125°C 8 SO MAX4092AUA -40°C to +125°C 8 µMAX MAX4094AUD -40°C to +125°C 14 TSSOP MAX4094ASD -40°C to +125°C 14 SO Low-Voltage Signal Conditioning Pin Configurations/Functional Diagrams TOP VIEW N.C. 1 8 N.C. IN- 2 7 VCC IN+ 3 6 OUT VEE 4 5 N.C. MAX4091 µMAX/SO OUT 1 MAX4091 5 VCC VEE 2 4 IN+ 3 IN- SOT23 OUT1 1 8 VCC IN1- 2 7 OUT2 IN1+ 3 6 IN2- VEE 4 5 IN2+ MAX4092 µMAX/SO OUT1 1 14 OUT4 IN1- 2 13 IN4- IN1+ 3 12 IN4+ VCC 4 MAX4094 11 VEE IN2+ 5 10 IN3+ IN2- 6 9 IN3- OUT2 7 8 OUT3 TSSOP/SO Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd. Beyond-the-Rails is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ 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 MAX4091/MAX4092/MAX4094 General Description The single MAX4091, dual MAX4092, and quad MAX4094 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 130µA of supply current. Even with this low current, the op amps are capable of driving a 1kΩ load, and the input-referred voltage noise is only 12nV/√Hz. In addition, these op amps can drive loads in excess of 2000pF. The precision performance of the MAX4091/MAX4092/ MAX4094 combined with their wide input and output dynamic range, low-voltage, single-supply operation, and very low supply current, make them an ideal choice for battery-operated equipment, industrial, and data acquisition and control applications. In addition, the MAX4091 is available in space-saving 5-pin SOT23, 8-pin µMAX, and 8-pin SO packages. The MAX4092 is available in 8-pin µMAX and SO packages, and the MAX4094 is available in 14-pin TSSOP and 14-pin SO packages. MAX4091/MAX4092/MAX4094 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-) ....................................................±10mA Output Short-Circuit Duration OUT shorted to GND or VCC .................................Continuous Continuous Power Dissipation (TA = +70°C) 5-Pin SOT23 (derate 7.1mW/°C above +70°C)...........571mW 8-Pin SO (derate 5.88mW/°C above +70°C)...............471mW 8-Pin µMAX (derate 4.1mW/°C above +70°C) ............330mW 14-Pin SO (derate 8.33mW/°C above +70°C).............667mW 14-Pin TSSOP (derate 9.1mW/°C above +70°C) ........727mW Operating Temperature Range .........................-40°C to +125°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°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 (VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 6.0 V VCC = 2.7V 115 165 VCC = 5V 130 185 DC CHARACTERISTICS Supply Voltage Range VCC Inferred from PSRR test 2.7 Supply Current ICC VCM = VCC/2 Input Offset Voltage VOS VCM = VEE to VCC 0.03 1.4 mV IB VCM = VEE to VCC 20 180 nA Input Offset Current IOS VCM = VEE to VCC 7 nA Input Common-Mode Range VCM Inferred from CMRR test VCC + 0.05 V Common-Mode Rejection Ratio CMRR (VEE - 0.05V) ≤ VCM ≤ (VCC + 0.05V) 71 90 dB Power-Supply Rejection Ratio PSRR 2.7V ≤ VCC ≤ 6V 86 100 dB VCC = 2.7V, RL = 100kΩ Sourcing 0.25V ≤ VOUT ≤ 2.45V Sinking 83 105 81 105 Sourcing 91 105 Input Bias Current Large-Signal Voltage Gain (Note 1) AVOL VCC = 2.7V, RL = 1kΩ 0.5V ≤ VOUT ≤ 2.2V 0.2 VEE - 0.05 Sinking VCC = 5.0V, RL = 100kΩ Sourcing 0.25V ≤ VOUT ≤ 4.75V Sinking VCC = 5.0V, RL = 1kΩ 0.5V ≤ VOUT ≤ 4.5V Output Voltage Swing High (Note 1) VOH |VCC - VOUT| Output Voltage Swing Low (Note 1) VOL |VOUT - VEE| 78 90 87 115 83 115 Sourcing 97 110 Sinking 84 100 µA dB RL = 100kΩ 15 69 RL = 1kΩ 130 210 RL = 100kΩ 15 70 RL = 1kΩ 80 220 mV mV AC CHARACTERISTICS Gain-Bandwidth Product Phase Margin GBWP RL = 100kΩ, CL = 100pF 500 kHz φM RL = 100kΩ, CL = 100pF 60 degrees Gain Margin Slew Rate 2 SR RL = 100kΩ, CL = 100pF 10 dB RL = 100kΩ, CL = 15pF 0.20 V/µs _______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps (VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA = +25°C.) PARAMETER SYMBOL Input-Noise Voltage Density eN Input-Noise Current Density CONDITIONS MIN TYP THD + N Capacitive-Load Stability CLOAD Settling Time tS Power-On Time tON Op-Amp Isolation UNITS f = 10kHz 12 nV/√Hz f = 10kHz 1.5 pA/√Hz 16 µVRMS f = 1kHz, RL = 10kΩ, CL = 15pF, AV = 1, VOUT = 2VP-P 0.003 % AV = 1 2000 pF To 0.1%, 2V step 12 µs VCC = 0 to 3V step, VIN = VCC/2, AV = 1 2 µs 125 dB Noise Voltage (0.1Hz to 10Hz) Total Harmonic Distortion Plus Noise MAX f = 1kHz (MAX4092/MAX4094) ELECTRICAL CHARACTERISTICS (VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA = TMIN to TMAX, unless otherwise noted. Typical values specified at TA = +25°C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 6.0 V DC CHARACTERISTICS Supply Voltage Range Supply Current Input Offset Voltage Input Offset Voltage Tempco Input Bias Current VCC Inferred from PSRR test ICC VCM = VCC/2 VOS VCM = VEE to VCC 2.7 VCC = 2.7V 200 VCC = 5V 225 ±3.5 ∆VOS/∆T ±2 IB VCM = VEE to VCC Input Offset Current IOS VCM = VEE to VCC Input Common-Mode Range VCM Inferred from CMRR test VEE - 0.05 µA mV µV/°C ±200 nA ±20 nA VCC + 0.05 V Common-Mode Rejection Ratio CMRR (VEE - 0.05V) ≤ VCM ≤ (VCC + 0.05V) 62 dB Power-Supply Rejection Ratio PSRR 2.7V ≤ VCC ≤ 6V 80 dB VCC = 2.7V, RL = 100kΩ 0.25V ≤ VOUT ≤ 2.45V Large-Signal Voltage Gain (Note 1) AVOL VCC = 2.7V, RL = 1kΩ 0.5V ≤ VOUT ≤ 2.2V Sourcing 82 Sinking 80 Sourcing 90 Sinking 76 VCC = 5V, RL = 100kΩ 0.25V ≤ VOUT ≤ 4.75V Sourcing 86 Sinking 82 VCC = 5V, RL = 1kΩ 0.5V ≤ VOUT ≤ 4.5V Sourcing 94 Sinking 80 dB Output Voltage Swing High (Note 1) VOH VCC - VOUT RL = 100kΩ 75 RL = 1kΩ 250 Output Voltage Swing Low (Note 1) VOL VOUT - VEE RL = 100kΩ 75 RL = 1kΩ 250 mV mV Note 1: RL is connected to VEE for AVOL sourcing and VOH tests. RL is connected to VCC for AVOL sinking and VOL tests. Note 2: All specifications are 100% tested at TA = +25°C. Specification limits over temperature (TA = TMIN to TMAX) are guaranteed by design, not production tested. _______________________________________________________________________________________ 3 MAX4091/MAX4092/MAX4094 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VCC = 5V, VEE = 0, TA = +25°C, unless otherwise noted.) GAIN AND PHASE vs. FREQUENCY 60 GAIN (dB) 40 20 0 PHASE -60 0 GAIN 60 0 20 PHASE 140 VCC 100 -60 0 VIN = 2.5V 120 MAX4091 toc03 120 40 GAIN (dB) GAIN 180 CL = 470pF AV = 1000 RL = ∞ 60 120 PHASE (DEGREES) 60 MAX4091 toc02 80 180 AV = 1000 NO LOAD PSRR (dB) MAX4091 toc01 80 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY PHASE (DEGREES) GAIN AND PHASE vs. FREQUENCY 80 60 VEE 40 20 0 1 10 100 -180 1000 10,000 -20 0.01 0.1 1 100 10 CHANNEL ISOLATION vs. FREQUENCY OFFSET VOLTAGE vs. TEMPERATURE OFFSET VOLTAGE vs. COMMON-MODE VOLTAGE VCM = 0 140 60 40 100 80 60 OFFSET VOLTAGE (µV) 80 120 100 80 60 1000 MAX4091 toc06 160 OFFSET VOLTAGE (mV) 100 40 40 VCC = 2.7V 20 0 -20 VCC = 6V -40 -60 20 20 0 0.01 -80 0 0.1 1 10 100 1000 10,000 -100 -60 -40 -20 0 20 40 60 80 100 120 140 -1 0 1 2 3 4 TEMPERATURE (°C) COMMON-MODE VOLTAGE (V) COMMON-MODE REJECTION RATIO vs. TEMPERATURE INPUT BIAS CURRENT vs. COMMON-MODE VOLTAGE INPUT BIAS CURRENT vs. TEMPERATURE VCM = -0.2V TO +5.2V VCM = -0.3V TO +5.3V VCM = -0.4V TO +5.4V 50 20 40 60 80 100 120 140 TEMPERATURE (°C) VCC = 2.7V 10 30 5 0 -5 -10 -15 3 4 5 6 125 -10 -20 -40 2 VCC = 2.7V 0 -25 COMMON-MODE VOLTAGE (V) 100 10 -30 1 VCC = 6V VCM = VCC 20 -20 0 MAX4091 toc09 MAX4091 toc08 15 7 40 INPUT BIAS CURRENT (nA) 80 VCC = 6V 20 INPUT BIAS CURRENT (nA) 90 -60 -40 -20 0 25 MAX4091 toc07 VCM = 0 TO 5V VCM = -0.1V TO +5.1V 6 5 FREQUENCY (kHz) 110 4 10 FREQUENCY (kHz) 120 60 1 FREQUENCY (kHz) VIN = 2.5V 70 0.1 FREQUENCY (kHz) 140 CHANNEL SEPARATION (dB) -40 0.01 -180 1000 10,000 100 MAX4091 toc05 0.1 MAX4901 toc04 -40 0.01 100 -120 -20 -120 -20 CMRR (dB) MAX4091/MAX4092/MAX4094 Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps VCM = 0 VCC = 6V -50 -25 0 25 50 75 TEMPERATURE (°C) _______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps 100 80 60 40 0 120 0 25 50 75 100 2 3 4 5 6 LARGE-SIGNAL GAIN vs. TEMPERATURE LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE 80 70 115 VCC = 2.7V RL TO VEE 60 110 RL = 1kW, 0.5V < VOUT < (VCC - 0.5V) RL TO VCC 100 VCC = 2.7V 95 VCC = 6V 500 RL = 1kW RL = 10kW 60 RL TO VCC 110 VCC = 6V 105 100 95 RL TO VEE 200 300 400 VOUT (mV) 500 600 400 500 600 180 RL TO VCC VCC = 6V, RL = 1kW 160 140 VCC = 2.7V, RL = 1kW 120 100 80 40 VCC = 6V, RL = 100kW VCC = 2.7V, RL = 100kW 20 0 80 100 200 60 90 85 50 300 220 MAX4091 toc17 115 RL = 100kW, 0.3V < VOUT < (VCC - 0.3V) 200 MINIMUM OUTPUT VOLTAGE vs. TEMPERATURE VCC = 2.7V VCC = 2.7V RL TO VCC 0 100 VOUT (mV) MINIMUM VOUT (nV) 90 120 LARGE-SIGNAL GAIN (dB) MAX4091 toc16 RL = 1MW 100 70 VCC = 6V RL TO VCC 0 20 40 60 80 100 120 140 LARGE-SIGNAL GAIN vs. TEMPERATURE 120 80 RL = 1kW RL = 10kW 80 TEMPERATURE (°C) LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE RL = 100kW 90 50 -60 -40 -20 0 600 RL = 100kW 60 80 400 200 300 VCC - VOUT (mV) 600 70 RL TO VEE 85 50 500 RL = 1MW 110 100 105 90 100 120 GAIN (dB) RL = 100kW RL = 10kW RL = 1kW 90 120 0 MAX4091 toc14 MAX4091 toc13 LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE 100 GAIN (dB) 50 1 400 200 300 VCC - VOUT (mV) 110 110 VCC = 6V RL TO VEE 60 SUPPLY VOLTAGE (V) RL = 1MW 100 80 TEMPERATURE (°C) 120 0 RL = 1kW 70 80 125 LARGE-SIGNAL GAIN (dB) -25 RL = 100kW 90 100 40 -50 RL = 1MW 100 140 60 20 GAIN (dB) 160 MAX4091 toc15 VCC = 2.7V 120 RL = 10kW 110 MAX4091 toc18 140 180 GAIN (dB) VCC = 5V 160 120 MAX4091 toc11 180 200 SUPPLY CURRENT PER AMP (µA) VOUT = VCM = VCC/2 200 SUPPLY CURRENT PER AMP (µA) MAX4091 toc10 220 LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE SUPPLY CURRENT PER AMPLIFIER vs. SUPPLY VOLTAGE MAX4091 toc12 SUPPLY CURRENT PER AMPLIFIER vs. TEMPERATURE -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX4091/MAX4092/MAX4094 Typical Operating Characteristics (continued) (VCC = 5V, VEE = 0, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = 5V, VEE = 0, TA = +25°C, unless otherwise noted.) MAXIMUM OUTPUT VOLTAGE vs. TEMPERATURE OUTPUT IMPEDANCE vs. FREQUENCY VCC = 2.7V, RL = 1kW 120 100 80 VCC = 6V, RL = 100kW VCC = 2.7V, RL = 100kW 40 100 10 1 20 0 100 INPUT REFERRED 1 0.1 0.01 -60 -40 -20 0 20 40 60 80 100 120 140 10 0.1 1 10 100 1,000 10,000 0.01 10 FREQUENCY (kHz) FREQUENCY (kHz) CURRENT-NOISE DENSITY vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY TOTAL HARMONIC DISTORTION PLUS NOISE vs. PEAK-TO-PEAK SIGNAL AMPLITUDE 4.5 4.0 0.1 MAX4091 toc23 0.1 MAX4091 toc22 5.0 AV = 1 2VP-P SIGNAL 80kHz LOWPASS FILTER AV = 1 1kHz SINE 22kHz FILTER RL TO GND THD + N (%) 3.0 2.5 2.0 0.01 THD + N (%) 3.5 RL = 10kW TO GND RL = 1kW RL = 2kW 0.01 1.5 RL = 100kW RL = 10kW 1.0 INPUT REFERRED 0.5 NO LOAD 0 0.001 0.001 0.01 1 0.1 10 10 FREQUENCY (kHz) 1000 100 10,000 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 PEAK-TO-PEAK SIGNAL AMPLITUDE (V) FREQUENCY (Hz) SMALL-SIGNAL TRANSIENT RESPONSE LARGE-SIGNAL TRANSIENT RESPONSE SMALL-SIGNAL TRANSIENT RESPONSE MAX4091 toc25 MAX4091 toc27 MAX4091 toc26 VCC = 5V, AV = 1, RL = 10kΩ VCC = 5V, AV = -1, RL = 10kΩ VCC = 5V, AV = 1, RL = 10kΩ VIN 50mV/div VIN 50mV/div VIN 2V/div VOUT 50mV/div VOUT 50mV/div VOUT 2V/div 2µs/div 6 1 0.1 TEMPERATURE (°C) MAX4091 toc24 60 VCM = VOUT = 2.5V MAX4091 toc21 VCC = 6V, RL = 1kW 140 1000 VOLTAGE-NOISE DENSITY (nV/ÖHz) 160 VOLTAGE-NOISE DENSITY vs. FREQUENCY MAX40912 toc20 RL TO VEE MAX4091 toc19 180 OUTPUT IMPEDANCE (W) (VCC - VOUT) (mV) 200 CURRENT-NOISE DENSITY (pA/√Hz) MAX4091/MAX4092/MAX4094 Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps 2µs/div 20µs/div _______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps SINK CURRENT vs. OUTPUT VOLTAGE SOURCE CURRENT vs. SUPPLY VOLTAGE VDIFF = 100mV -2 OUTPUT CURRENT (mA) VIN 2V/div VOUT 2V/div -6 -8 -10 -12 -14 VCC = 2.7V -16 VCC = 6V VDIFF = 100mV 25 OUTPUT CURRENT (mA) -4 30 MAX4091 toc30 0 MAX4091 toc28 VCC = 5V, AV = -1, RL = 10kΩ MAX4091 toc29 LARGE-SIGNAL TRANSIENT RESPONSE VCC = 6V 20 15 10 VCC = 2.7V 5 -18 -20 0 0 20µs/div 0.5 1.0 1.5 2.0 2.5 3.0 1.0 2.0 OUTPUT VOLTAGE (V) 3.0 4.0 5.0 6.0 SUPPLY VOLTAGE (V) Pin Description PIN NAME FUNCTION MAX4091 SOT23 1 MAX4091 SO/µMAX 6 — — OUT Amplifier Output 2 4 4 11 VEE Negative Supply 3 3 — — IN+ Noninverting Input 4 2 — — IN- Inverting Input 5 7 8 4 VCC Positive Supply — 1, 5, 8 — — N.C. No Connection. Not internally connected. — — 1 1 OUT1 — — 2 2 IN1- Amplifier 1 Inverting Input — — 3 3 IN1+ Amplifier 1 Noninverting Input — — 5 5 IN2+ Amplifier 2 Noninverting Input — — 6 6 IN2- Amplifier 2 Inverting Input — — 7 7 OUT2 — — — 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 MAX4092 MAX4094 Amplifier 1 Output Amplifier 2 Output Amplifier 3 Output Amplifier 4 Output _______________________________________________________________________________________ 7 MAX4091/MAX4092/MAX4094 Typical Operating Characteristics (continued) (VCC = 5V, VEE = 0, TA = +25°C, unless otherwise noted.) MAX4091/MAX4092/MAX4094 Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps Detailed Description The single MAX4091, dual MAX4092 and quad MAX4094 op amps combine excellent DC accuracy with rail-to-rail 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, industrial, and data acquisition and control applications. Applications Information Rail-to-Rail Inputs and Outputs The MAX4091/MAX4092/MAX4094’s input commonmode range extends 50mV 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 MAX4091/MAX4092/ MAX4094 can be used in applications with commonmode signals, at or even beyond the supplies, without the problems associated with typical op amps. The MAX4091/MAX4092/MAX4094’s output voltage swings to within 15mV of the supplies with a 100kΩ load. This rail-to-rail swing at the input and the output substantially increases the dynamic range, especially in low-supply-voltage applications. Figure 1 shows the input and output waveforms for the MAX4092, configured as a unity-gain noninverting buffer operating from a single 3V supply. The input signal is 3.0VP-P, a 1kHz sinusoid centered at 1.5V. The output amplitude is approximately 2.98VP-P. match the effective resistance seen at each input. Connect resistor R3 between the noninverting input and ground when using the op amp in an inverting configuration (Figure 2a); connect resistor R3 between the noninverting input and the input signal when using the op amp in a noninverting configuration (Figure 2b). Select R3 to equal the parallel combination of R1 and R2. High source resistances will degrade noise performance, due to the the input current noise (which is multiplied by the source resistance). Input Stage Protection Circuitry The MAX4091/MAX4092/MAX4094 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 1.7kΩ resistors in series (Figure 3). 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 +25°C). Input bias current for the ICs (±20nA) is specified for small differential input voltages. For large differential input voltages (exceeding VF), this protection circuitry increases the input current at IN+ and IN-: INPUT CURRENT = [(VIN + ) − (VIN − )] − VF 2 ✕ 1.7kΩ Output Loading and Stability 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 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 above VEE. 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. Even with their low quiescent current of less than 130µA per op amp, the MAX4091/MAX4092/MAX4094 are well suited for driving loads up to 1kΩ while maintaining DC accuracy. Stability while driving heavy capacitive loads is another key advantage over comparable CMOS rail-to-rail op amps. 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. The input bias currents of the MAX4091/MAX4092/ MAX4094 are typically less than 20nA. 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, The MAX4091/MAX4092/MAX4094 can drive capacitive loads in excess of 2000pF under certain conditions (Figure 4). When driving capacitive loads, the greatest potential for instability occurs when the op amp is sourcing approximately 200µA. Even in this case, stability is maintained with up to 400pF of output capaci- Input Offset Voltage 8 _______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps Because the MAX4091/MAX4092/MAX4094 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 MAX4091/MAX4092/MAX4094 have a typical supply current of 130µA 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 MAX4092 to buffer the inputs of a multi-channel analogto-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 MAX4091/MAX4092/ MAX4094, 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 slewrate limited. With the noninverting input to a voltage follower held at midsupply (Figure 9), when the supply steps from 0 to VCC, the output settles in approximately 2µs for VCC = 3V (Figure 10a) and 8µs for VCC = 5V (Figure 10b). Power Supplies and Layout The MAX4091/MAX4092/MAX4094 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 0.1µF 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. Chip Information MAX4091 TRANSISTOR COUNT: 168 MAX4092 TRANSISTOR COUNT: 336 MAX4094 TRANSISTOR COUNT: 670 PROCESS: Bipolar _______________________________________________________________________________________ 9 MAX4091/MAX4092/MAX4094 tance. If the output sources either more or less current, stability is increased. These devices perform well with a 1000pF pure capacitive load (Figure 5). Figures 6a, 6b, and 6c show the performance with a 500pF load in parallel with various load resistors. To increase stability while driving large-capacitive loads, connect a pullup resistor to VCC at the output to decrease the current 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 7). This resistor improves the phase margin of the circuit by isolating the load capacitor from the op amp’s output. Figure 8a shows the MAX4092 driving 5000pF (RL ≥ 100kΩ), while Figure 8b adds a 47Ω isolation resistor. MAX4091/MAX4092/MAX4094 Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps Test Circuits/Timing Diagrams VCC = 3V VEE = 0 R2 VIN 1V/div R1 VIN VOUT MAX409_ VOUT 1V/div R3 R3 = R2 II R1 200µs/div Figure 1. Rail-to-Rail Input and Output Operation Figure 2a. Reducing Offset Error Due to Bias Current: Inverting Configuration R3 1.7kΩ VIN IN+ TO INTERNAL CIRCUITRY VOUT MAX409_ R2 R3 = R2 II R1 R1 IN– 1.7kΩ Figure 2b. Reducing Offset Error Due to Bias Current: Noninverting Configuration 10 TO INTERNAL CIRCUITRY Figure 3. Input Stage Protection Circuitry ______________________________________________________________________________________ MAX4091 MAX4092 MAX4094 Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps 10,000 CAPACITIVE LOAD (pF) RL = ∞ UNSTABLE REGION VIN 50mV/div 1000 VOUT 50mV/div VCC = 5V VOUT = VCC/2 RL TO VEE AV = 1 100 1 10 100 10µs/div RESISTIVE LOAD (kΩ) Figure 4. Capacitive-Load Stable Region Sourcing Current Figure 5. MAX4092 Voltage Follower with 1000pF Load RL = 5kΩ RL = 20kΩ VIN 50mV/div VIN 50mV/div VOUT 50mV/div VOUT 50mV/div 10µs/div Figure 6a. MAX4092 Voltage Follower with 500pF Load (RL = 5kΩ) 10µs/div Figure 6b. MAX4092 Voltage Follower with 500pF Load (RL = 20kΩ) ______________________________________________________________________________________ 11 MAX4091/MAX4092/MAX4094 Test Circuits/Timing Diagrams (continued) MAX4091/MAX4092/MAX4094 Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps Test Circuits/Timing Diagrams (continued) RL = ∞ VIN 50mV/div RS VOUT MAX409_ CL VIN VOUT 50mV/div 10µs/div Figure 6c. MAX4092 Voltage Follower with 500pF Load (RL = ∞) VIN 50mV/div VIN 50mV/div VOUT 50mV/div VOUT 50mV/div 10µs/div Figure 8a. Driving a 5000pF Capacitive Load 12 Figure 7. Capacitive-Load Driving Circuit 10µs/div Figure 8b. Driving a 5000pF Capacitive Load with a 47Ω Isolation Resistor ______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps 5V VCC VIN 1V/div 2 7 1kΩ 6 MAX409_ 3 VOUT 4 VOUT 500mV/div 1kΩ 5µs/div Figure 10a. Power-Up Settling Time (VCC = +3V) Figure 9. Power-Up Test Configuration VIN 2V/div VOUT 1V/div 5µs/div Figure 10b. Power-Up Settling Time (VCC = +5V) ______________________________________________________________________________________ 13 MAX4091/MAX4092/MAX4094 Test Circuits/Timing Diagrams (continued) Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps 8LUMAXD.EPS SOT5L.EPS MAX4091/MAX4092/MAX4094 Package Information 14 ______________________________________________________________________________________ Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps SOICN.EPS ______________________________________________________________________________________ 15 MAX4091/MAX4092/MAX4094 Package Information (continued) Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps TSSOP,NO PADS.EPS MAX4091/MAX4092/MAX4094 Package Information (continued) 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 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.