LMV422 Dual Rail-to-Rail Output Operational Amplifier with Power Select General Description Features The LMV422 dual rail-to-rail output amplifier offers a power select pin (PS) that allows the user to select one of two power modes depending on the level of performance desired. This is ideal for AC coupled circuits where the circuit needs to be kept active to maintain a quiescent charge on the coupling capacitors with minimum power consumption. n Supply voltage n Supply current per channel — Low power mode — Full power mode n Input common mode voltage range n CMRR n Output voltage swing n Input offset voltage n Bandwidth — Low power mode — Full power mode n Stable for AV ≥ +2 or AV ≤ −1 For portable applications, the LMV422 operates in low power mode consuming only 2 µA of supply current per channel at a bandwidth of 27 kHz. This allows the user to reduce the power consumption of an amplifier while maintaining an active circuit. For additional bandwidth and output current drive the amplifier can be switched to full power mode with 8 MHz bandwidth while consuming only 400 µA per channel. The LMV422 features a rail-to-rail output voltage swing in addition to an input common mode range that includes ground. The LMV422 is designed for closed loop gains of plus two (or minus one) or greater. The LMV422 is offered in 10-Pin MSOP miniature package to ease the adoption in applications where board area is at a premium. 2.7V to 5.5V 2 µA 400 µA −0.3V to 3.8V 85 dB Rail-to-Rail 1 mV 27 kHz 8 MHz Applications n AC coupled circuits n Portable instrumentation n Smoke detectors Typical Application 20109835 AC Coupled Application © 2005 National Semiconductor Corporation DS201098 www.national.com Dual Rail-to-Rail Output Operational Amplifier with Power Select February 2005 LMV422 Absolute Maximum Ratings Soldering Information (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance(Note 2) Human Body − Supply Voltage (V - V ) Storage Temperature Range Junction Temperature (Note 4) 2.7V to 5.5V Temperature Range ± 2V + 260˚C Supply Voltage (V+ – V−) 200V VIN Differential 235˚C Wave Soldering Lead Temp. (10 sec) Operating Ratings (Note 1) 2000V Machine Model Infrared or Convection (20 sec) −40˚C to +85˚C Package Thermal Resistance (θJA) 2.5V to 5.5V 10-Pin MSOP −65˚C to +150˚C 210˚C/W +150˚C 5V Full Power Mode Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = 0V, VCM = VO = V+/2, PS = V−. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 6) Typ (Note 5) Max (Note 6) 1 4 5.5 0.1 1 VOS Input Offset Voltage ∆VOS Input Offset Voltage Difference VOS in Full Power Mode − VOS in Low Power Mode TC VOS Input Offset Average Drift IB Input Bias Current CMRR Common Mode Rejection Ratio VCM Stepped from 0V to 3.5V 68 60 85 PSRR Power Supply Rejection Ratio V+ = 2.7V to 5V 66 60 90 CMVR Input Common Mode Voltage Range CMRR ≥ 50 dB −0.3 AVOL Large Signal Voltage Gain VO = 0.75V to 4.25V RL = 1 MΩ 72 70 100 VO = 0.75V to 4.25V RL = 10 kΩ 75 70 102 RL = 10 kΩ to V+/2 4.93 4.88 4.97 RL = 1 MΩ to V+/2 4.94 4.89 4.98 VO Output Swing High Output Swing Low ISC IS Output Short Circuit Current (Note 9) Slew Rate Gain Bandwidth Product en Input-Referred Voltage Noise www.national.com µV/C pA dB dB 3.8 V RL = 1 MΩ to V+/2 25 120 170 Sourcing, VO = 0V VID = 100 mV 3 5 Sinking, VO = 5V VID = −100 mV 9 16 400 1.8 mV mA 650 900 µA 3.8 V/µs 8 MHz f = 100 kHz 20 f = 1 kHz 25 2 V dB 180 230 VO = 3V, AV = +2 SR GBW mV 5 33 PS ≤ 0.5V mV 2 RL = 10 kΩ to V+/2 Supply Current Per Channel Units nV/ (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = 0V, VCM = VO = V+/2, PS = V−. Boldface limits apply at the temperature extremes. Symbol Parameter in Input-Referred Current Noise tLF Time from Low Power Mode to Full Power Mode THPS Full Power Mode Voltage Threshold IPS Input Current PS pin(Note 7) Conditions Min (Note 6) f = 1 kHz Typ (Note 5) Max (Note 6) 0.006 Units pA/ 210 ns 0.5 V −2 µA 5V Low Power Mode Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = 0V, VCM = VO = V+/2, PS = V+ or Open. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 6) Typ (Note 5) Max (Note 6) 1 4 5.5 0.1 1 VOS Input Offset Voltage ∆VOS Input Offset Voltage Difference VOS in Full Power Mode − VOS in Low Power Mode TC VOS Input Offset Average Drift IB Input Bias Current CMRR Common Mode Rejection Ratio VCM Stepped from 0V to 3.5V 60 55 82 PSRR Power Supply Rejection Ratio V+ = 2.7V to 5V 62 60 90 CMVR Input Common-Mode Voltage Range CMRR ≥ 50 dB 0 AVOL Large Signal Voltage Gain RL = 1 MΩ VO = 0.75 to 4V 62 54 72 VO Output Swing High RL = 1 MΩ 4.94 4.89 4.98 Output Swing Low RL = 1 MΩ Output Short Circuit Current Sourcing, VO = 0V VID = 200 mV 40 140 Sinking, VO = 5V VID = −200 mV 25 130 ISC (Note 9) IS Supply Current per channel PS ≥ 4. 5V SR Slew Rate VO = 3V, AV = +2 GBW Gain Bandwidth Product en Input-Referred Voltage Noise in Input-Referred Current Noise tFL Time from Full Power Mode to Low Power Mode THPS Low Power Mode Voltage Threshold IPS Input Current PS pin (Note 7) mV µV/C 5 pA dB dB 3.5 2 V dB V 200 250 mV µA 3.5 4.5 µA 14 V/ms 27 kHz f = 100 kHz 40 f = 1 kHz 60 f = 1 kHz 0.06 500 4.5 nV/ pA/ ns V 8 3 mV 2 150 8 Units nA www.national.com LMV422 5V Full Power Mode Electrical Characteristics LMV422 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics. Note 2: Human body model, 1.5 kΩ in series with 100 pF, Machine Model, 0Ω in series with 200 pF. Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150˚C. Note 4: The maximum power dissipation is a function of TJ(MAX), θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) - TA)/ θJA . All numbers apply for packages soldered directly onto a PC board. Note 5: Typical values represent the most likely parametric norm. Note 6: All limits are guaranteed by testing or statistical analysis. Note 7: Positive current corresponds to current flowing into the device. Note 8: Slew rate is the average of the rising and falling slew rates. Note 9: Offset voltage average drift determined by dividing the change in VOS at temperature extremes into the total temperature change. Connection Diagram 10-Pin MSOP 20109806 Top View Ordering Information Package 10-Pin MSOP 3 x 5 mm Part Number LMV422MM LMV422MMX Package Marking AJ1A Transport Media 1k Units Tape and Reel 3.5k Units Tape and Reel Simplified Schematic 20109818 www.national.com 4 NSC Drawing MUB10A Unless otherwise specified, V+ = 5V, TA = 25˚C, PS = V+ for − Full Power Mode, PS = V for Low Power Mode. Supply Current vs. Supply Voltage per Channel (Full Power Mode) Supply Current vs. Supply Voltage per Channel (Low Power Mode) 20109801 20109802 Gain and Phase vs. Frequency Gain and Phase vs. Frequency 20109812 20109813 Gain and Phase vs. Frequency Gain and Phase vs. Frequency 20109814 20109815 5 www.national.com LMV422 Typical Performance Characteristics LMV422 Typical Performance Characteristics Unless otherwise specified, V+ = 5V, TA = 25˚C, PS = V+ for Full Power Mode, PS = V− for Low Power Mode. (Continued) Phase Margin vs. Gain for Various Capacitive Load Phase Margin vs. Gain for Various Capacitive Load 20109823 20109824 Input Offset Voltage vs. Output Voltage Input Offset Voltage vs. Output Voltage 20109817 20109816 Noise vs. Frequency PSRR vs. Frequency 20109832 www.national.com 20109833 6 Full Power Mode, PS = V− for Low Power Mode. (Continued) Small Signal Non-Inverting Response Small Signal Non-Inverting Response 20109820 20109821 Small Signal Non-Inverting Response Small Signal Non-Inverting Response 20109822 20109836 Large Signal Non-Inverting Response Large Signal Non-Inverting Response 20109837 20109838 7 www.national.com LMV422 Typical Performance Characteristics Unless otherwise specified, V+ = 5V, TA = 25˚C, PS = V+ for LMV422 Application Information The LMV422 is a dual rail-to-rail output amplifier that can be switched between two active power modes. The power select pin (PS) provides a method to optimize the power consumption, bandwidth and short circuit current. When the PS pin is set to greater than 4.5V (Figure 1a) or left open, the LMV422 is in Low Power Mode operating at a bandwidth of 27 kHz and consuming only 2 µA of supply current per channel. Setting the PS pin to less than 0.5V, switches the LMV422 to Full Power Mode with a bandwidth of 8 MHz and supply current of 400 uA per channel (Figure 2b).. The PS pin should not exceed the supply voltage. The active power modes of the two amplifiers can be set independently. 20109808 Figure 1b Full Power Mode 20109807 Figure 1a Low Power Mode FIGURE 1. The LMV422 PS pin has an internal pull up and a logic level control gate that makes it easy for the PS pin to be controlled by the output of a logic gate or the output pin of a microcon- troller. The following figures show the three typical output configurations for logic gates and microcontrollers. 20109811 Figure 2c 20109809 Figure 2a 20109810 Figure 2b FIGURE 2. CAPACITIVE LOAD TOLERANCE The LMV422 is optimized for maximum bandwidth when operating at a minimum closed loop gain of +2 or −1, therefore, it is not recommended to be configured as a buffer. Like many other op amps, the LMV422 may oscillate when the applied load appears capacitive. The threshold of the oscillation varies both with load and circuit gain (see Phase Margin vs. Gain for various capacitive loads curves). The load capacitance interacts with the amplifier’s output resistance to create an additional pole. If this pole frequency is www.national.com too low, it will degrade the amplifier’s phase margin so that the amplifier is no longer stable. Figure 3a and 3b show the addition of a small value resistor RISO or RX (50Ω to 100Ω) in series with the op amps output. Figure 3b shows the addition of a capacitor CF (5 pF to 10 pF) between the inverting input and the output pin. This addition capacitor returns the phase margin to a safe value without interfering with lower frequency circuit operation. Note that in all cases, the output will ring heavily when the load capacitance is near the threshold for oscillation. 8 LMV422 Application Information (Continued) 20109825 Figure 3a 20109826 Figure 3b FIGURE 3. AC COUPLED CIRCUITS The two power modes makes the LMV422 ideal for AC coupled circuit where the circuit needs to be kept active to maintain a quiescent charge on the coupling capacitors with minimum power consumption. them when placed in the shut down state. When the amplifiers are turned on again, the quiescent DC voltages must reestablish themselves. During this time, the amplifier’s output is not usable because the output signal is a mixture of the amplified input signal and the charging voltage on the coupling capacitors. The settling time can range from a several milliseconds to several seconds depending on the resistor and capacitor values. When the LMV422 is placed into the low power mode the power consumption is minimal but the amplifier is active to maintain the quiescent DC voltage on the coupling capacitors and the transition back to the operational high power mode is fast, within few hundred nanoseconds. The active low power mode of the LMV422 separates the two critical aspects of a low power AC amplifier design. The values of the gain resistors, bias resistors, and coupling capacitors can be chosen independently of the turn on and stabilization time. Figure 4 shows a schematic of an inverting and non-inverting AC coupled amplifiers using the LMV422 with the PS pins controlled by I/O ports of a microcontroller. The advantage of the low power active mode for AC coupled amplifiers is the elimination of the time needed to reestablish a quiescent operating point when the amplifier is switched to a full power mode. When amplifiers without a low power active mode are used in low power applications, there are two ways to minimize power consumption. The first is turning off the amplifiers by switching off power to the op amps using a transistor switch. The second is using an amplifier with a shut down pin. Both of these methods have the problem of allowing the coupling capacitors, C1, C2, C3, C4, and C5, to discharge the quiescent DC voltage stored on 20109834 FIGURE 4. RESISTIVE LOAD The LMV422 has a minimum current drive of 3 mA in full power mode. The minimum resistive load should be 10 kΩ The current drive in the low power mode is 140 uA, the minimum resistive load should be 100 kΩ. 9 www.national.com Dual Rail-to-Rail Output Operational Amplifier with Power Select Physical Dimensions inches (millimeters) unless otherwise noted 10-Pin MSOP NS Package Number MUB10A National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. 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