January 2005 LMP8272, LMP8277 High Common Mode, Gain of 14, Precision Voltage Difference Amplifiers General Description Features The LMP™8272, LMP8277 are fixed gain differential ampli- n n n n n n n n n n n n fiers with a -2V to 27V input common mode voltage range and a supply voltage range of 4.5V to 5.5V. The LMP8272, LMP8277 are precision amplifiers which will detect, amplify and filter small differential signals in the presence of high common mode voltages. The gain is fixed at 14 and is adequate to drive an ADC to full scale in most cases. This fixed gain is achieved in two separate stages, a pre-amplifier with gain of +7 and a second stage amplifier with a gain of +2. The internal signal path between these two stages is brought out on two pins that provide a connection for a filter network. The LMP8272, LMP8277 will function with reduced specifications over the extended common mode input voltage range of -5 to 36 Volts. This feature makes the device suitable for applications with load dump in automotive systems. Typical Values, TA = 25˚C Input Offset Voltage 1mV max TCVos (LMP8272) 15µV/˚C max TCVos (LMP8277) 30µV/˚C max CMRR 80dB Min Extended CMVR -5V to 36V Output Voltage Swing Rail to Rail Bandwidth 80KHz Operating Temperature Range (Ambient) -40˚C to 125˚C Operating Temperature Range (bare die) -40˚C to 150˚C Supply Voltage 4.5V to 5.5V Supply Current 1mA Applications n Fuel Injection Control n Low Side Driver Configuration Current Sensing n Power Management Systems Typical Application Typical Application: Low side Current Sensing 20130901 LMP™ is a trademark of National Semiconductor Corporation. © 2005 National Semiconductor Corporation DS201309 www.national.com LMP8272,LMP8277 High Common Mode, Gain of 14, Precision Voltage Difference Amplifiers PRELIMINARY LMP8272, LMP8277 High Common Mode, Gain of 14, Precision Voltage Difference Amplifier Absolute Maximum Ratings (Note 1) Junction Temperature (Note 3) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Soldering Information ESD Tolerance (Note 2) +150˚C max Infrared or Convection (20 sec) 235˚C Wave Soldering Lead Temp. (10 sec) 260˚C Human Body Model ± 4000V ± 2000V For input pins only For All other pins Machine Model Operating Ratings (Note 1) Temperature Range (Note 3) 200V Supply Voltage (VS - GND) CMVR Continuous Transient (300 ms) Storage Temperature Range 5.75V -40˚C to +125˚C Bare Die Junction Temperature(Note 3) -40˚C to +150˚C Supply Voltage (VS – GND) -5 to 42 Volts 4.5V to 5.5V Package Thermal Resistance (θJA (Note 3)) -TBD to 45 Volts 8–Pin SOIC -65˚C to +150˚C 5V Electrical Characteristics Packaged devices(Note 3) 190˚C/W (Note 7) Unless otherwise specified, all limits guaranteed for TA = 25˚C, VS = 5V, GND= 0, -2V≤VCM ≤27V. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min Typ (Note 4) ± 0.25 ±6 ±6 VOS Input Offset Voltage VCM = Vs/2 TC VOS Input Offset Voltage Drift LMP8272 TC VOS Input Offset Voltage Drift LMP8277 A2 IB Input Bias Current of A2 (Note 5) IS Supply Current 0.6 TBD RCM Input impedance Common Mode RDM Input impedance Differential Mode CMVR Input Common-Mode Voltage Range ECMVR Extended Common-Mode Voltage Range DC CMRR DC Common Mode Rejection Ratio -2V≤VCM≤ 27V -5V≤VCM≤ 36V AC CMRR AC Common Mode Rejection Ratio -2V≤VCM≤ 27V -2V≤VCM≤ 27V PSRR Power Supply Rejection Ratio 4.5V≤VS≤ 5.5V RF-INT Filter Resistor TCRF-INT Filter Resistor Drift AV Total Gain Continuous 1.0 mV µV/˚C 1.0 1.2 TBD mA 160 200 240 KΩ 320 400 480 KΩ -2 +27 V -5 36 V f = 1KHz TBD dB f = 10KHz TBD 97 dB 100 A2 Output Voltage Swing 103 TBD VOL RL= 100KΩ on Output V/V ±1 ± 25 ppm/˚C 0.01 Volts 0.01 Volts % 4.80 VOL VOH KΩ ppm/˚C 14 VOH A2 VOUT µA dB TBD TBD RL= 100KΩ on Output µV/˚C 80 80 Gain Drift A1 Output Voltage Swing Units ± 15 ± 30 ± 20 Gain Error A1 VOUT Max 4.80 SR Slew Rate (Note 6) 0.7 V/µs BW Bandwidth 80 KHz www.national.com 2 (Note 7) (Continued) Unless otherwise specified, all limits guaranteed for TA = 25˚C, VS = 5V, GND= 0, -2V≤VCM ≤27V. Boldface limits apply at the temperature extremes. Symbol Noise Parameter Conditions Min Typ (Note 4) Max Units 0.1Hz ro 10Hz TBD µVpp Spectral Density TBD nV/√Hz 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 Tables. Note 2: Human body model, 1.5 kΩ in series with 100 pF. Machine model: 0Ω in series with 200 pF. Note 3: 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 4: Typical values represent the most likely parametric norm. Note 5: Positive current corresponds to current flowing into the device. Note 6: Slew rate is the average of the rising and falling slew rates. Note 7: Electrical table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device. Connection Diagram 8–Pin SOIC 20130902 Top View The overall offset of the LMP8272, LMP8277 is minimized by trimming amplifier A1. This is done so that the output referred offset of A1 cancels the input referred offset of A2 or 7VOS1 = -VOS2 Because of this offset voltage relationship, the offset of each individual amplifier stage maybe more than the limit specified for the overall system in the datasheet tables. Care must be given when pin 3 and 4, A1 and A2, are connected to each other. If the signal going from A1 to A2 is amplified or attenuated (by use of amplifiers and resistors), the overall LMP8272, LMP8277 offset will be affected as a result. Filtering the signal between A1 and A2 or simply connecting the two pins will not change the offset of the LMP8272, LMP8277. Referencing input referred offset voltages, the following relationship holds: Application Note The LMP8272, LMP8277 are single supply amplifier with a fixed gain of 14 and an extended common mode voltage range of -2V to 36V. The fixed gain is achieved in two separate stages, a pre-amplifier with gain of +7 and a second stage amplifier with gain of +2. A block diagram of the LMP8272, LMP8277 is shown in Figure 1. 20130903 If the signal on pin 3 is scaled, attenuated or amplified, by a factor X, then the offset of the overall system will become: FIGURE 1. 3 www.national.com LMP8272, LMP8277 High Common Mode, Gain of 14, Precision Voltage Difference Amplifier 5V Electrical Characteristics LMP8272, LMP8277 High Common Mode, Gain of 14, Precision Voltage Difference Amplifier Application Note be above the limits indicated in the electrical characteristics tables. (Continued) This represents a value that the LMP8272 and LMP8277 have not been optimized and trimmed for and may very well www.national.com 4 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. 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. 2. 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