LMV2011

LMV2011 High Precision, Rail-to-Rail Output Operational Amplifier April 2004 LMV2011 High Precision, Rail-to-Rail Output Operational Amplifier General Description The LMV2011 is a new precision amplifier that offers unprecedented accuracy and stability at an affordable price and is offered in miniature (SOT23-5) package and in 8 lead SOIC package. This device utilizes patented techniques to measure and continually correct the input offset error voltage. The result is an amplifier which is ultra stable over time and temperature. It has excellent CMRR and PSRR ratings, and does not exhibit the familiar 1/f voltage and current noise increase that plagues traditional amplifiers. The combination of the LMV2011 characteristics makes it a good choice for transducer amplifiers, high gain configurations, ADC buffer amplifiers, DAC I-V conversion, and any other 2.7V-5V application requiring precision and long term stability. Other useful benefits of the LMV2011 are rail-to-rail output, a low supply current of 930µA, and wide gain-bandwidth product of 3MHz. These extremely versatile features found in the LMV2011 provide high performance and ease of use. Features (For Vs = 5V, Typical unless otherwise noted) n Low Guaranteed Vos over temperature n Low Noise with no 1/f n High CMRR n High PSRR n High AVOL n Wide gain-bandwidth product n High slew rate n Low supply current n Rail-to-rail output n No external capacitors required 35µV 35nV/ 130dB 120dB 130dB 3MHz 4V/µs 930µA 30mV Applications n Precision Instrumentation Amplifiers n Thermocouple Amplifiers n Strain Gauge Bridge Amplifier Connection Diagrams 5-Pin SOT23 8-Pin SOIC 20051502 20051538 Top View Top View Ordering Information Package 5-Pin SOT23 8-Pin SOIC Part Number LMV2011MF LMV2011MFX LMV2011MA LMV2011MAX Package Marking A84A LMV2011MA Transport Media 1k Units Tape and Reel 3k Units Tape and Reel 95 Units/Rail 2.5k Units Tape and Reel NSC Drawing MF05A M08A © 2004 National Semiconductor Corporation DS200515 www.national.com LMV2011 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance Human Body Model Machine Model Supply Voltage Common-Mode Input Voltage Differential Input Voltage Current At Input Pin 2000V 200V 5.5V −0.3≤ VCM ≤ VCC +0.3V Current At Output Pin Current At Power Supply Pin Junction Temperature (TJ) Lead Temperature (soldering 10 sec.) 30mA 50mA 150˚C +300˚C Operating Ratings (Note 1) Supply Voltage Storage Temperature Range Operating Temperature Range 2.7V to 5.25V −65˚C to 150˚C 0˚C to 70˚C = 25˚C, V+ ± Supply Voltage 30mA 2.7V DC Electrical Characteristics = 2.7V, V- = 0V, V Symbol VOS CM Unless otherwise specified, all limits guaranteed for T = 1.35V, VO = 1.35V and RL > 1MΩ. Boldface limits apply at the temperature extremes. Conditions Min Typ 0.8 0.5 0.015 0.006 2.5 -3 6 9 −0.3 ≤ VCM ≤ 0.9V 0 ≤ VCM ≤ 0.9V 2.7V ≤ V+ ≤ 5V RL = 10kΩ RL = 2kΩ 130 120 130 124 2.665 2.655 2.68 0.033 RL = 2kΩ to 1.35V VIN(diff) = ± 0.5V 2.630 2.615 2.65 0.061 0.085 0.105 5 3 5 3 1.20 1.50 0.060 0.075 95 90 95 90 95 90 90 85 5 Max 25 35 10 12 J Parameter Input Offset Voltage Offset Calibration Time Units µV ms µV/˚C µV/month µV pA pA MΩ dB dB TCVOS Input Offset Voltage Long-Term Offset Drift Lifetime VOS Drift IIN IOS RIND CMRR PSRR AVOL Input Current Input Offset Current Input Differential Resistance Common Mode Rejection Ratio Power Supply Rejection Ratio Open Loop Voltage Gain dB VO Output Swing RL = 10kΩ to 1.35V VIN(diff) = ± 0.5V V V IO Output Current Sourcing, VO = 0V VIN(diff) = ± 0.5V Sinking, VO = 5V V IN(diff) = ± 0.5V 12 18 0.05 0.919 mA ROUT IS Output Impedance Supply Current Ω mA www.national.com 2 LMV2011 2.7V AC Electrical Characteristics Symbol GBW SR θm Gm en in enp-p trec ts Parameter Gain-Bandwidth Product Slew Rate Phase Margin Gain Margin Input-Referred Voltage Noise Input-Referred Current Noise Input-Referred Voltage Noise Input Overload Recovery Time Output Settling Time TJ = 25˚C, V+ = 2.7V, V - = 0V, VCM = 1.35V, VO = 1.35V, and RL > 1MΩ. Boldface limits apply at the temperature extremes. Conditions Min Typ 3 4 60 −14 35 150 RS = 100Ω, DC to 10Hz 850 50 AV = −1, RL = 2kΩ 1V Step 1% 0.1% 0.01% 0.9 49 100 J Max Units MHz V/µs Deg dB nV/ fA/ nVpp ms µs 5V DC Electrical Characteristics 5V, V = 0V, V Symbol VOS CM Unless otherwise specified, all limits guaranteed for T = 2.5V, VO = 2.5V and RL > 1MΩ. Boldface limits apply at the temperature extremes. Parameter Conditions Min Typ 0.12 0.5 0.015 0.006 2.5 -3 6 9 −0.3 ≤ VCM ≤ 3.2 0 ≤ VCM ≤ 3.2 2.7V ≤ V+ ≤ 5V RL = 10kΩ RL = 2kΩ 130 120 130 132 4.96 4.95 4.978 0.040 RL = 2kΩ to 2.5V VIN(diff) = ± 0.5V 4.895 4.875 4.919 0.091 100 90 95 90 105 100 95 90 5 Max 25 35 10 12 = 25˚C, V+ = Units µV ms µV/˚C µV/month µV pA pA MΩ dB dB Input Offset Voltage Offset Calibration Time TCVOS Input Offset Voltage Long-Term Offset Drift Lifetime VOS Drift IIN IOS RIND CMRR PSRR AVOL Input Current Input Offset Current Input Differential Resistance Common Mode Rejection Ratio Power Supply Rejection Ratio Open Loop Voltage Gain dB VO Output Swing RL = 10kΩ to 2.5V VIN(diff) = ± 0.5V 0.070 0.085 V 0.115 0.140 8 6 8 6 V IO Output Current Sourcing, VO = 0V VIN(diff) = ± 0.5V Sinking, VO = 5V V IN(diff) = ± 0.5V 15 17 mA 3 www.national.com LMV2011 5V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for T J = 25˚C, V+ = 5V, V- = 0V, V Symbol ROUT IS CM = 2.5V, VO = 2.5V and RL > 1MΩ. Boldface limits apply at the temperature extremes. (Continued) Parameter Conditions Min Typ 0.05 0.930 1.20 1.50 Max Units Ω mA Output Impedance Supply Current per Channel 5V AC Electrical Characteristics Symbol GBW SR θm Gm en in enp-p trec ts Parameter Gain-Bandwidth Product Slew Rate Phase Margin Gain Margin Input-Referred Voltage Noise Input-Referred Current Noise Input-Referred Voltage Noise Input Overload Recovery Time Output Settling Time TJ = 25˚C, V+ = 5V, V - = 0V, VCM = 2.5V, VO = 2.5V, and RL > 1MΩ. Boldface limits apply at the temperature extremes. Conditions Min Typ 3 4 60 −15 35 150 RS = 100Ω, DC to 10Hz 850 50 AV = −1, RL = 2kΩ 1V Step 1% 0.1% 0.01% 0.8 36 100 Max Units MHz V/µs deg dB nV/ fA/ nVpp ms us Note 1: Absolute Maximum Ratings indicate limits beyond which damage 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 test conditions, see the Electrical Characteristics. www.national.com 4 LMV2011 Typical Performance Characteristics TA=25C, VS= 5V unless otherwise specified. Supply Current vs. Supply Voltage Offset Voltage vs. Supply Voltage 20051524 20051525 Offset Voltage vs. Common Mode Offset Voltage vs. Common Mode 20051535 20051534 Voltage Noise vs. Frequency Input Bias Current vs. Common Mode 20051504 20051503 5 www.national.com LMV2011 Typical Performance Characteristics PSRR vs. Frequency (Continued) PSRR vs. Frequency 20051507 20051506 Output Sourcing @ 2.7V Output Sourcing @ 5V 20051526 20051527 Output Sinking @ 2.7V Output Sinking @ 5V 20051528 20051529 www.national.com 6 LMV2011 Typical Performance Characteristics Max Output Swing vs. Supply Voltage (Continued) Max Output Swing vs. Supply Voltage 20051530 20051531 Min Output Swing vs. Supply Voltage Min Output Swing vs. Supply Voltage 20051532 20051533 CMRR vs. Frequency Open Loop Gain and Phase vs. Supply Voltage 20051505 20051508 7 www.national.com LMV2011 Typical Performance Characteristics Open Loop Gain and Phase vs. RL @ 2.7V (Continued) Open Loop Gain and Phase vs. RL @ 5V 20051509 20051510 Open Loop Gain and Phase vs. CL @ 2.7V Open Loop Gain and Phase vs. CL @ 5V 20051511 20051512 Open Loop Gain and Phase vs. Temperature @ 2.7V Open Loop Gain and Phase vs. Temperature @ 5V 20051536 20051537 www.national.com 8 LMV2011 Typical Performance Characteristics THD+N vs. AMPL (Continued) THD+N vs. Frequency 20051514 20051513 0.1Hz − 10Hz Noise vs. Time 20051515 9 www.national.com LMV2011 Application Information THE BENEFITS OF LMV2011 NO 1/f NOISE Using patented methods, the LMV2011 eliminates the 1/f noise present in other amplifiers. That noise, which increases as frequency decreases, is a major source of measurement error in all DC-coupled measurements. Lowfrequency noise appears as a constantly-changing signal in series with any measurement being made. As a result, even when the measurement is made rapidly, this constantlychanging noise signal will corrupt the result. The value of this noise signal can be surprisingly large. For example: If a conventional amplifier has a flat-band noise level of 10nV/ and a noise corner of 10Hz, the RMS noise at 0.001Hz . This is equivalent to a 0.50µV peak-to-peak is 1µV/ error, in the frequency range 0.001 Hz to 1.0 Hz. In a circuit with a gain of 1000, this produces a 0.50mV peak-to-peak output error. This number of 0.001 Hz might appear unreasonably low, but when a data acquisition system is operating for 17 minutes, it has been on long enough to include this error. In this same time, the LMV2011 will only have a 0.21mV output error. This is smaller by 2.4 x. Keep in mind that this 1/f error gets even larger at lower frequencies. At the extreme, many people try to reduce this error by integrating or taking several samples of the same signal. This is also doomed to failure because the 1/f nature of this noise means that taking longer samples just moves the measurement into lower frequencies where the noise level is even higher. The LMV2011 eliminates this source of error. The noise level is constant with frequency so that reducing the bandwidth reduces the errors caused by noise. Another source of error that is rarely mentioned is the error voltage caused by the inadvertent thermocouples created when the common "Kovar type" IC package lead materials are soldered to a copper printed circuit board. These steelbased leadframe materials can produce over 35µV/˚C when soldered onto a copper trace. This can result in thermocouple noise that is equal to the LMV2011 noise when there is a temperature difference of only 0.0014˚C between the lead and the board! For this reason, the lead-frame of the LMV2011 is made of copper. This results in equal and opposite junctions which cancel this effect. The extremely small size of the SOT-23 package results in the leads being very close together. This further reduces the probability of temperature differences and hence decreases thermal noise. OVERLOAD RECOVERY The LMV2011 recovers from input overload much faster than most chopper-stabilized opamps. Recovery from driving the amplifier to 2X the full scale output, only requires about 40ms. Many chopper-stabilized amplifiers will take from 250ms to several seconds to recover from this same overload. This is because large capacitors are used to store the unadjusted offset voltage. 20051516 FIGURE 1. The wide bandwidth of the LMV2011 enhances performance when it is used as an amplifier to drive loads that inject transients back into the output. ADCs (Analog-to-Digital Converters) and multiplexers are examples of this type of load. To simulate this type of load, a pulse generator producing a 1V peak square wave was connected to the output through a 10pF capacitor. (Figure 1) The typical time for the output to recover to 1% of the applied pulse is 80ns. To recover to 0.1% requires 860ns. This rapid recovery is due to the wide bandwidth of the output stage and large total GBW. NO EXTERNAL CAPACITORS REQUIRED The LMV2011 does not need external capacitors. This eliminates the problems caused by capacitor leakage and dielectric absorption, which can cause delays of several seconds from turn-on until the amplifier’s error has settled. MORE BENEFITS The LMV2011 offers the benefits mentioned above and more. It has a rail-to-rail output and consumes only 950µA of supply current while providing excellent DC and AC electrical performance. In DC performance, the LMC2001 achieves 130dB of CMRR, 120dB of PSRR and 130dB of open loop gain. In AC performance, the LMV2011 provides 3MHz of gain-bandwidth product and 4V/µs of slew rate. HOW THE LMV2011 WORKS The LMV2011 uses new, patented techniques to achieve the high DC accuracy traditionally associated with chopperstabilized amplifiers without the major drawbacks produced by chopping. The LMV2011 continuously monitors the input offset and corrects this error. The conventional chopping process produces many mixing products, both sums and differences, between the chopping frequency and the incoming signal frequency. This mixing causes large amounts of distortion, particularly when the signal frequency approaches the chopping frequency. Even without an incoming signal, the chopper harmonics mix with each other to produce even more trash. If this sounds unlikely or difficult to understand, look at the plot (Figure 2), of the output of a typical (MAX432) chopper-stabilized opamp. This is the output when there is no incoming signal, just the amplifier in a gain of -10 with the input grounded. The chopper is operating at about 150Hz; the rest is mixing products. Add an input signal and the noise gets much worse. Compare this plot with Figure 3 of the LMV2011. This data was taken under the exact same conditions. The auto-zero action is visible at about 30kHz but note the absence of mixing products at other frequencies. As a result, the LMV2011 has very low distortion of 0.02% and very low mixing products. www.national.com 10 LMV2011 Application Information (Continued) PRECISION STRAIN-GAUGE AMPLIFIER This Strain-Gauge amplifier (Figure 4) provides high gain (1006 or ~60 dB) with very low offset and drift. Using the resistors’ tolerances as shown, the worst case CMRR will be greater than 108 dB. The CMRR is directly related to the resistor mismatch. The rejection of common-mode error, at the output, is independent of the differential gain, which is set by R3. The CMRR is further improved, if the resistor ratio matching is improved, by specifying tighter-tolerance resistors, or by trimming. 20051517 FIGURE 2. 20051518 FIGURE 4. Extending Supply Voltages and Output Swing by Using a Composite Amplifier Configuration: In cases where substantially higher output swing is required with higher supply voltages, arrangements like the ones shown in Figure 5 and Figure 6 could be used. These configurations utilize the excellent DC performance of the LMV2011 while at the same time allow the superior voltage and frequency capabilities of the LM6171 to set the dynamic performance of the overall amplifier. For example, it is possible to achieve ± 12V output swing with 300MHz of overall GBW (AV = 100) while keeping the worst case output shift due to VOS less than 4mV. The LMV2011 output voltage is kept at about mid-point of its overall supply voltage, and its input common mode voltage range allows the V- terminal to be grounded in one case (Figure 5, inverting operation) and tied to a small non-critical negative bias in another (Figure 6, non-inverting operation). Higher closed-loop gains are also possible with a corresponding reduction in realizable bandwidth. Table 1 shows some other closed loop gain possibilities along with the measured performance in each case. 20051504 FIGURE 3. INPUT CURRENTS The LMV2011’s input currents are different than standard bipolar or CMOS input currents in that it appears as a current flowing in one input and out the other. Under most operating conditions, these currents are in the picoamp level and will have little or no effect in most circuits. These currents tend to increase slightly when the common-mode voltage is near the minus supply. (See the typical curves.) At high temperatures such as 85˚C, the input currents become larger, 0.5nA typical, and are both positive except when the VCM is near V−. If operation is expected at low common-mode voltages and high temperature, do not add resistance in series with the inputs to balance the impedances. Doing this can cause an increase in offset voltage. A small resistance such as 1kΩ can provide some protection against very large transients or overloads, and will not increase the offset significantly. 11 www.national.com LMV2011 Application Information (Continued) 20051520 20051519 FIGURE 6. It should be kept in mind that in order to minimize the output noise voltage for a given closed-loop gain setting, one could minimize the overall bandwidth. As can be seen from Equation 1 above, the output noise has a square-root relationship to the Bandwidth. In the case of the inverting configuration, it is also possible to increase the input impedance of the overall amplifier, by raising the value of R1, without having to increase the feedback resistor, R2, to impractical values, by utilizing a "Tee" network as feedback. See the LMC6442 data sheet (Application Notes section) for more details on this. FIGURE 5. TABLE 1. Composite Amplifier Measured Performance AV 50 100 100 500 1000 R1 Ω 200 100 1k 200 100 R2 Ω 10k 10k 100k 100k 100k C2 pF 8 10 0.67 1.75 2.2 BW MHz 3.3 2.5 3.1 1.4 0.98 SR en p-p (V/µs) (mVPP) 178 174 170 96 64 37 70 70 250 400 In terms of the measured output peak-to-peak noise, the following relationship holds between output noise voltage, en p-p, for different closed-loop gain, AV, settings, where −3dB Bandwidth is BW: 20051521 FIGURE 7. www.national.com 12 LMV2011 Application Information LMV2011 AS ADC INPUT AMPLIFIER (Continued) 1/f corner frequency = 100Hz AV = 2000 Measurement time = 100 sec Bandwidth = 2Hz This example will result in about 2.2 mVPP (1.9 LSB) of output noise contribution due to the opamp alone, compared to about 594µVPP (less than 0.5 LSB) when that opamp is replaced with the LMV2011 which has no 1/f contribution. If the measurement time is increased from 100 seconds to 1 hour, the improvement realized by using the LMV2011 would be a factor of about 4.8 times (2.86mVPP compared to 596µV when LMV2011 is used) mainly because the LMV2011 accuracy is not compromised by increasing the observation time. D) Copper leadframe construction minimizes any thermocouple effects which would degrade low level/high gain data conversion application accuracy (see discussion under "The Benefits of the LMV2011" section above). E) Rail-to-Rail output swing maximizes the ADC dynamic range in 5-Volt single-supply converter applications. Below are some typical block diagrams showing the LMV2011 used as an ADC amplifier (Figure 7 and Figure 8). The LMV2011 is a great choice for an amplifier stage immediately before the input of an ADC (Analog-to-Digital Converter), whether AC or DC coupled. See Figure 7 and Figure 8. This is because of the following important characteristics: A) Very low offset voltage and offset voltage drift over time and temperature allow a high closed-loop gain setting without introducing any short-term or long-term errors. For example, when set to a closed-loop gain of 100 as the analog input amplifier for a 12-bit A/D converter, the overall conversion error over full operation temperature and 30 years life of the part (operating at 50˚C) would be less than 5 LSBs. B) Fast large-signal settling time to 0.01% of final value (1.4µs) allows 12 bit accuracy at 100KHZ or more sampling rate. C) No flicker (1/f) noise means unsurpassed data accuracy over any measurement period of time, no matter how long. Consider the following opamp performance, based on a typical low-noise, high-performance commerciallyavailable device, for comparison: Opamp flatband noise = 8nV/ 20051522 FIGURE 8. 13 www.national.com LMV2011 Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SOT23 NS Package Number MF0A5 8-Pin SOIC NS Package Number M08A www.national.com 14 LMV2011 High Precision, Rail-to-Rail Output Operational Amplifier Notes 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. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. BANNED SUBSTANCE COMPLIANCE National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. 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