LT1997-3 Precision, Wide Voltage Range Gain Selectable Amplifier Description Features Pin Configurable as a Difference Amplifier, Inverting Amplifier or Noninverting Amplifier nn 91dB Minimum DC CMRR (Gain = 1) nn 65dB AC CMRR (at 100kHz, Gain = 1) nn 0.006% (60ppm) Maximum Gain Error (Gain = 1) nn 1ppm/C Maximum Gain Error Drift nn 2ppm Maximum Gain Nonlinearity nn 160V Common Mode Voltage Range nn Wide Supply Voltage Range: 3.3V to 50V nn Rail-to-Rail Output nn 350A Supply Current nn 60V Maximum Op Amp Offset Voltage nn 1.1MHz -3dB Bandwidth (Gain = 1) nn Low-Power Shutdown: 20A nn Space-Saving MSOP and DFN Packages The LT(R)1997-3 combines a precision operational amplifier with highly-matched resistors to form a one-chip solution for accurately amplifying voltages. Gains from -13 to +14 with accuracy of 0.006% (60ppm) can be achieved using no external components. The LT1997-3 is particularly well suited for use as a difference amplifier, where the excellent resistor matching results in a common mode rejection ratio of greater than 91dB. nn The amplifier features a 60V maximum input offset voltage and a -3dB bandwidth of 1.1MHz (Gain = 1). The LT1997-3 operates from any supply voltage from 3.3V to 50V and draws only 350A supply current. The output typically swings to within 100mV of either supply rail. The resistors maintain their excellent matching over temperature; the matching temperature coefficient is guaranteed less than 1ppm/C. The resistors are extremely linear with voltage, resulting in a gain nonlinearity of less than 2ppm. Applications High Side or Low Side Current Sensing Bidirectional Wide Common Mode Range Current Sensing nn High Voltage to Low Voltage Level Translation nn Industrial Data-Acquisition Front-Ends nn Replacement for Isolation Circuits nn Differential to Single-Ended Conversion nn nn The LT1997-3 is fully specified at 5V and 15V supplies and from -40C to 125C. The device is available in space saving 16-lead MSOP and 4mm x 4mm DFN14 packages. L, LT, LTC, LTM, Linear Technology, Over-The-Top and the Linear logo are registered trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners. Typical Application Typical Distribution of CMRR (G = 1) Gain = 1 Difference Amplifier VSOURCE = -28V TO 26.5V 1200 15V V+ LT1997-3 -INA -INB -INC VS = 15V VCM = -28V TO +26.5V 1000 4625 UNITS FROM 3 RUNS 7.5k 22.5k - 22.5k RSENSE 1 RC 1 OUT + 22.5k 7.5k 2.5k LOAD +INA +INB +INC 45k REF2 45k REF1 VOUT = 1mV/mA SHDN V- -15V NUMBER OF UNITS 2.5k 800 600 400 200 0 -30 -20 -10 0 10 CMRR (V/V = ppm) 20 30 19973 TA01b 19973 TA01a 19973f For more information www.linear.com/LT1997-3 1 LT1997-3 Absolute Maximum Ratings (Note 1) Supply Voltages (V+ to V-).........................................60V +INA, -INA (Note 2).......................................... V- 160V +INB, -INB, +INC, -INC (Note 2)............................... (V- + 80V) to (V- - 0.3V) REF, REF1, REF2..................... (V- + 60V) to (V- - 0.3V) SHDN...................................... (V+ + 0.3V) to (V- - 0.3V) Output Current (Continuous) (Note 6).....................50mA Output Short-Circuit Duration (Note 3)...........................................Thermally Limited Temperature Range (Notes 4, 5) LT1997I-3.................................................-40 to 85C LT1997H-3.............................................. -40 to 125C Maximum Junction Temperature........................... 150C Storage Temperature Range.......................-65 to 150C MSOP Lead Temperature (Soldering, 10 sec)......... 300C Pin Configuration TOP VIEW +INA 1 +INB 3 TOP VIEW 14 -INA 15 V- +INA 1 16 -INA 12 -INB +INB 3 14 -INB 11 NC +INC REF1 REF2 V- NC 4 +INC 5 SHDN 6 10 -INC 9 V+ REF 7 8 5 6 7 8 -INC V+ SHDN OUT 12 11 10 9 MS PACKAGE VARIATION: MS16 (12) 16-LEAD PLASTIC MSOP OUT TJMAX = 150C, JA = 130C/W DF PACKAGE 14(12)-LEAD (4mm x 4mm) PLASTIC DFN TJMAX = 150C, JA = 45C/W , JC = 3C/W EXPOSED PAD (PIN 15) IS V-, MUST BE SOLDERED TO PCB Order Information http://www.linear.com/product/LT1997-3#orderinfo LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE LT1997IDF-3#PBF LT1997IDF-3#TRPBF 19973 14-Lead (4mm x 4mm) Plastic DFN -40C to 85C LT1997HDF-3#PBF LT1997HDF-3#TRPBF 19973 14-Lead (4mm x 4mm) Plastic DFN -40C to 125C LT1997IMS-3#PBF LT1997IMS-3#TRPBF 19973 16-Lead Plastic MSOP -40C to 85C LT1997HMS-3#PBF LT1997HMS-3#TRPBF 19973 16-Lead Plastic MSOP -40C to 125C *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for parts specified with wider operating temperature ranges. Parts ending with PBF are RoHS and WEEE compliant. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. 2 19973f For more information www.linear.com/LT1997-3 LT1997-3 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, -40C < TA < 85C for I-grade parts, -40C < TA < 125C for H-grade parts, otherwise specifications are at TA = 25C. Difference Amplifier Configuration, V+ = 15V, V- = -15V, VCM = VOUT = VREF = VREF1 = VREF2 = 0V. VCMOP is the common mode voltage of the internal op amp. SYMBOL PARAMETER CONDITIONS G VOUT = 10V G=1 Gain Error MIN TYP 0.001 l 0.001 G=3 l 0.002 G=9 l G/T Gain Drift vs Temperature (Note 6) VOUT = 10V GNL Gain Nonlinearity VOUT = 10V 0.2 l 1 l VOS Op Amp Offset Voltage (Note 9) V- < VCMOP < V+ - 1.75V 20 l VOS/T IB Op Amp Offset Voltage Drift (Note 6) V- < VCMOP < V+ - 1.75V Op Amp Input Bias Current V- + 0.25V < V CMOP RIN CMRR Op Amp Input Offset Current Input Impedance (Note 8) Common Mode Rejection Ratio, MS16 Package Common Mode G=1 G=3 G=9 Differential G=1 G=3 G=9 G = 1, VCM = -28V to +26.5V 26 17.4 14.5 k k k l l l 38 12.6 4.2 91 87 90 86 96 94 91 87 83 80 81 77 81 78 90 86 96 94 -30 -160 -15 -15 45 15 5 106 52 17.4 5.8 k k k dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB V V V V G = 9, VCM = -15V to +14.7V l G = 1, VCM = -28V to +26.5V l l l l l G = 9, VCM = -15V to +14.7V l VCM Input Voltage Range (Note 7) +INA/-INA +INA/-INA, +INC/-INC Connected to Ground +INB/-INB +INC/-INC ppm ppm V V V/C 22.5 15 12.5 l G = 1, VCM = -90V to +90V, +INB = -INB = 0V, VS = 25V G = 1, VCM = -120V to +120V, +INC = -INC = 0V, VS = 25V, TA = -40C to 125C G = 1, VCM = -160V to +160V, +INC = -INC = 0V, VS = 25V, TA = -40C to 85C G = 3, VCM = -15V to +17.6V 2 3 60 200 1.5 19 12.6 10.5 l Common Mode Rejection Ratio, DF14 Package % % % % % % ppm/C l l l G = 3, VCM = -15V to +17.6V CMRR 0.006 0.012 0.015 0.02 0.03 0.04 1 l V- + 0.25V < VCMOP < V+ - 1.75V l l l l 2 UNITS -5 -15 -3 -10 l IOS 0.5 l < V+ - 1.75V MAX 0.5 5 15 3 10 nA nA nA nA 99 112 101 94 91 91 98 103 26.5 160 17.6 14.7 19973f For more information www.linear.com/LT1997-3 3 LT1997-3 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, -40C < TA < 85C for I-grade parts, -40C < TA < 125C for H-grade parts, otherwise specifications are at TA = 25C. Difference Amplifier Configuration, V+ = 15V, V- = -15V, VCM = VOUT = VREF = VREF1 = VREF2 = 0V. VCMOP is the common mode voltage of the internal op amp. SYMBOL PARAMETER CONDITIONS R/R Reference Divider Matching Error R RREF1 - RREF2 = R RREF1 +RREF2 2 Available in MS16 Package Only PSRR Power Supply Rejection Ratio eni Input Referred Noise Voltage Density VS = 1.65V to 25V, VCM = VOUT = Mid-Supply (Note 9) f = 1kHz G=1 G=3 G=9 f = 0.1Hz to 10Hz G=1 G=3 G=9 No Load ISINK = 5mA No Load ISOURCE = 5mA 50 to V+ 50 to V- VOUT = 5V Input Referred Noise Voltage VOL ISC Output Voltage Swing Low (Referred to V-) Output Voltage Swing High (Referred to V+) Short-Circuit Output Current SR Slew Rate BW Small Signal -3dB Bandwidth tS Settling Time VOH VS MIN l l l l l l 10 10 0.45 G=1 G=3 G=9 G=1 0.1%, VOUT = 10V 0.01%, VOUT = 10V G=3 0.1%, VOUT = 10V 0.01%, VOUT = 10V G=9 0.1%, VOUT = 10V 0.01%, VOUT = 10V tON Turn-On Time VIL SHDN Input Logic Low (Referred to V+) l VIH SHDN Input Logic High (Referred to V+) l ISHDN SHDN Pin Current 4 114 l l Supply Voltage Supply Current MAX 0.001 0.006 0.012 l l IS TYP l dB 50 30 22 nV/Hz nV/Hz nV/Hz 1.4 1 0.8 100 280 100 530 28 30 0.75 150 500 180 900 VP-P VP-P VP-P mV mV mV mV mA mA V/s 1100 700 300 kHz kHz kHz 14.6 95 s s 13.6 29 s s 13.8 29 s s V V s 3 3.3 50 50 -2.5 -1.2 V V -10 -15 A 350 400 600 25 70 A A A A l 20 l % % 124 16 Active, VSHDN V+ - 1.2V Active, VSHDN V+ - 1.2V Shutdown, VSHDN V+ - 2.5V Shutdown, VSHDN V+ - 2.5V UNITS 19973f For more information www.linear.com/LT1997-3 LT1997-3 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, -40C < TA < 85C for I-grade parts, -40C < TA < 125C for H-grade parts, otherwise specifications are at TA = 25C. Difference Amplifier Configuration, V+ = 5V, V- = 0V, VCM = VOUT = VREF = VREF1 = VREF2 = Mid-Supply. VCMOP is the common mode voltage of the internal op amp. SYMBOL PARAMETER CONDITIONS G VOUT = 1V to 4V G=1 Gain Error MIN TYP 0.001 l 0.001 G=3 l 0.002 G=9 l G/T Gain Drift vs Temperature (Note 6) VOUT = 1V to 4V GNL Gain Nonlinearity VOUT = 1V to 4V Op Amp Offset Voltage (Note 9) V- < V VOS CMOP 0.2 l 20 l Op Amp Offset Voltage Drift (Note 6) V- < VCMOP < V+ - 1.75V IB Op Amp Input Bias Current V- + 0.25V < VCMOP < V+ - 1.75V RIN CMRR Op Amp Input Offset Current Input Impedance (Note 8) Common Mode Rejection Ratio, MS16 Package 26 17.4 14.5 k k k 38 12.6 4.2 90 88 90 87 96 94 90 88 90 87 96 94 45 15 5 100 52 17.4 5.8 k k k dB dB dB dB dB dB dB dB dB dB dB dB % % l l G = 1, VCM = -2.5V to +4.0V l G = 3, VCM = 0V to +3.5V l G = 9, VCM = 0V to +3.3V l Reference Divider Matching Error R RREF1 - RREF2 = R RREF1 +RREF2 2 Available in MS16 Package Only PSRR Power Supply Rejection Ratio eni Input Referred Noise Voltage Density VS = 1.65V to 25V, VCM = VOUT = Mid-Supply (Note 9) f = 1kHz G=1 G=3 G=9 V V V/C 22.5 15 12.5 G = 9, VCM = 0V to +3.3V R/R 60 200 1.5 19 12.6 10.5 l l l l 2 ppm l l l l Common Mode Rejection Ratio, DF14 Package % % % % % % ppm/C l G = 3, VCM = 0V to +3.5V CMRR 0.006 0.012 0.015 0.02 0.03 0.04 1 -5 -15 -3 -10 V- + 0.25V < VCMOP < V+ - 1.75V Common Mode G=1 G=3 G=9 Differential G=1 G=3 G=9 G = 1, VCM = -2.5V to +4.0V 0.5 l l IOS UNITS 1 < V+ - 1.75V VOS/T MAX 0.5 108 96 101 107 0.001 114 nA nA nA nA 103 l l 5 15 3 10 0.006 0.012 124 dB 50 30 22 nV/Hz nV/Hz nV/Hz 19973f For more information www.linear.com/LT1997-3 5 LT1997-3 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, -40C < TA < 85C for I-grade parts, -40C < TA < 125C for H-grade parts, otherwise specifications are at TA = 25C. Difference Amplifier Configuration, V+ = 5V, V- = 0V, VCM = VOUT = VREF = VREF1 = VREF2 = Mid-Supply. VCMOP is the common mode voltage of the internal op amp. SYMBOL PARAMETER CONDITIONS SR f = 0.1Hz to 10Hz G=1 G=3 G=9 Output Voltage Swing Low (Referred to V-) No Load ISINK = 5mA Output Voltage Swing High (Referred to V+) No Load ISOURCE = 5mA Short-Circuit Output Current 50 to V+ 50 to V- Slew Rate VOUT = 3V BW Small signal -3dB Bandwidth tS Settling Time MIN TYP 10 10 0.45 1.4 1 0.8 15 280 15 450 27 25 0.75 Input Referred Noise Voltage VOL VOH ISC VS l l l l l l l G=1 G=3 G=9 G=1 0.1%, VOUT = 2V 0.01%, VOUT = 2V G=3 0.1%, VOUT = 2V 0.01%, VOUT = 2V G=9 0.1%, VOUT = 2V 0.01%, VOUT = 2V Supply Voltage l tON Turn-On Time VIL SHDN Input Logic Low (Referred to V+) l VIH SHDN Input Logic High (Referred to V+) l ISHDN SHDN Pin Current IS Supply Current UNITS 50 500 50 800 VP-P VP-P VP-P mV mV mV mV mA mA V/s 1100 700 300 kHz kHz kHz 5.4 91 s s 6 21 s s 7 36 s s V V s 3 3.3 50 50 22 l Active, VSHDN V+ - 1.2V Active, VSHDN V+ -1.2V Shutdown, VSHDN V+ - 2.5V Shutdown, VSHDN V+ - 2.5V Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: See "Common Mode Voltage Range" and "High Common Mode Voltage Difference Amplifiers" in the Applications Information section of this data sheet for other considerations when taking +INA/-INA pins to 160V and +INB/-INB/+INC/-INC pins to +80V. Note 3: A heat sink may be required to keep the junction temperature below absolute maximum. This depends on the power supply, input voltages and the output current. Note 4: The LT1997I-3 is guaranteed functional over the operating temperature range of -40C to 85C. The LT1997H-3 is guaranteed functional over the operating temperature range of -40C to 125C. 6 MAX -2.5 -1.2 -10 -15 A 330 370 525 20 40 A A A A l 15 l V V Note 5: The LT1997I-3 is guaranteed to meet specified performance from -40C to 85C. The LT1997H-3 is guaranteed to meet specified performance from -40C to 125C. Note 6: This parameter is not 100% tested. Note 7: The Input Voltage Range numbers specified in the table guarantee that the internal op amp operates in its normal operating region. The Input voltage range can be significantly higher if the internal op amp operates in its Over-The-Top(R) operating region. See "Common Mode Voltage Range" in the Applications Information section to determine the valid input voltage range under various operating conditions. Note 8: Input impedance is tested by a combination of direct measurements and correlation to the CMRR and gain error tests. Note 9: Offset voltage, offset voltage drift and PSRR are defined as referred to the internal op amp. You can calculate output offset as follows. In the case of balanced source resistance, VOS,OUT = (VOS * NOISEGAIN) + (IOS * 22.5k) + (IB * 22.5k * (1- RP/RN)) where RP and RN are the total resistance at the op amp positive and negative terminal, respectively. 19973f For more information www.linear.com/LT1997-3 LT1997-3 Typical Performance Characteristics configuration, unless otherwise noted. 22.5k - + 22.5k NUMBER OF UNITS 1000 22.5k 22.5k 800 500 VS = 15V VCM = -28V TO +26.5V 4625 UNITS FROM 3 RUNS 600 400 2.5k 22.5k 450 22.5k 400 NUMBER OF UNITS 1200 Typical Distribution of CMRR (G = 1) 22.5k 350 300 - + 22.5k Typical Distribution of CMRR (G = 3) 2709 UNITS FROM 2 RUNS 2.5k 250 1400 VS = 25V VCM = -160V TO +160V +INC = -INC = 0V 200 150 100 200 -20 -10 0 10 CMRR (V/V = ppm) 20 0 -100 -75 -50 -25 0 25 50 CMRR (V/V = ppm) 30 19973 G01 2.5k 22.5k 800 800 VS = 15V VCM = -15V TO +14.7V 400 22.5k 22.5k 700 4450 UNITS FROM 3 RUNS 600 22.5k 600 200 -10 -5 0 5 CMRR (V/V=ppm) 10 - + NUMBER OF UNITS 600 400 300 4864 UNITS 200 FROM 3 RUNS 22.5k 400 300 0 -300 -100 0 100 GAIN ERROR (ppm) 200 300 19973 G07 4864 UNITS FROM 3 RUNS 400 300 100 1200 22.5k 22.5k 1000 22.5k 0 -150 -100 -50 0 50 GAIN ERROR (ppm) 100 - + VS = 15V VOUT = 10V G=1 600 400 0 4864 UNITS FROM 3 RUNS 0 150 19973 G06 CMRR vs Frequency 22.5k 800 200 -200 22.5k 200 200 100 30 500 Typical Distribution of Gain Nonlinearity 4864 UNITS FROM 3 RUNS 500 7.5k - + 19973 G05 NUMBER OF UNITS 2.5k 20 VS = 15V VOUT = 10V 22.5k 7.5k 700 0 -50 -40 -30 -20 -10 0 10 20 30 40 50 GAIN ERROR (ppm) 15 VS = 15V VOUT = 10V 22.5k - + 2.5k -10 0 10 CMRR (V/V = ppm) 800 600 22.5k 500 Typical Distribution of Gain Error (G = 9) 700 -20 Typical Distribution of Gain Error (G = 3) VS = 15V VOUT = 10V 19973 G04 800 400 19973 G03 100 0 -15 600 0 -30 100 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2.0 GAIN NONLINEARITY (ppm) 19973 G08 140 COMMON-MODE REJECTION RATIO (dB) NUMBER OF UNITS 1000 75 NUMBER OF UNITS - + 2.5k 4450 UNITS FROM 3 RUNS 22.5k 800 Typical Distribution of Gain Error (G = 1) NUMBER OF UNITS 22.5k 1000 19973 G02 Typical Distribution of CMRR (G = 9) 1200 7.5k VS = 15V VCM = -15V TO +17.6V 200 50 0 -30 22.5k - + 7.5k 1200 NUMBER OF UNITS Typical Distribution of CMRR (G = 1) TA = 25C, VS = 15V, Difference Amplifier 120 100 80 60 40 G=1 G=3 G=9 20 0 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M 19973 G09 19973f For more information www.linear.com/LT1997-3 7 LT1997-3 Typical Performance Characteristics TA = 25C, VS = 15V, Difference Amplifier configuration, unless otherwise noted. Typical Distribution of Op Amp PSRR 800 700 1200 6360 UNITS FROM 3 RUNS 1000 4864 UNITS FROM 3 RUNS Typical Gain Error for RL = 10k G = 1 (Curves Offset for Clarity) VS = 1.65V to 25V VS = 18V OUTPUT ERROR (2mV/DIV) Typical Distribution of Op Amp Offset Voltage NUMBER OF UNITS NUMBER OF UNITS 600 500 400 300 800 600 400 200 -20 0 20 OFFSET VOLTAGE (V) 40 0 -1.5 60 -1 -0.5 0 0.5 PSRR (V/V) VS = 10V -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) 1.5 19973 G12 19973 G11 19973 G10 Typical Gain Error for RL = 5k G = 1 (Curves Offset for Clarity) Typical Gain Error for Low Supply Voltages, G = 1 (Curves Offset for Clarity) Typical Gain Error for RL = 2k G = 1 (Curves Offset for Clarity) VS = 18V OUTPUT ERROR (2mV/DIV) VS = 18V OUTPUT ERROR (2mV/DIV) 1 VS = 15V VS = 12V VS = 10V -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) VS = 5V, RL=10k OUTPUT ERROR (2mV/DIV) -40 VS = 15V VS = 12V VS = 10V 19973 G13 OUTPUT ERROR (2mV/DIV) -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) 19973 G16 4 5 6 Typical Gain Error for RL = 2k G = 3 (Curves Offset for Clarity) VS = 18V VS = 10V VS = 2.5V, RL=1k 19973 G15 Typical Gain Error for RL = 5k G = 3 (Curves Offset for Clarity) VS = 18V VS = 12V VS = 5V, RL=1k 19973 G14 Typical Gain Error for RL = 10k G = 3 (Curves Offset for Clarity) VS = 15V VS = 5V, RL=2k -6 -5 -4 -3 -2 -1 0 1 2 3 OUTPUT VOLTAGE (V) -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) VS = 18V OUTPUT ERROR (2mV/DIV) 0 -60 OUTPUT ERROR (2mV/DIV) VS = 12V 200 100 8 VS = 15V VS = 15V VS = 12V VS = 10V -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) 19973 G17 VS = 15V VS = 12V VS = 10V -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) 19973 G18 19973f For more information www.linear.com/LT1997-3 LT1997-3 Typical Performance Characteristics TA = 25C, VS = 15V, Difference Amplifier configuration, unless otherwise noted. Typical Gain Error for RL = 10k G = 9 (Curves Offset for Clarity) Typical Gain Error for RL = 5k G = 9 (Curves Offset for Clarity) VS = 18V VS = 15V VS = 12V VS = 10V OUTPUT ERROR (2mV/DIV) VS = 18V OUTPUT ERROR (2mV/DIV) OUTPUT ERROR (2mV/DIV) VS = 18V VS = 15V VS = 12V VS = 10V -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) 80 8 40 60 6 30 40 4 20 20 2 0 0 -2 -20 VS = 15V VOUT = 10V RL = 10k 10 UNITS G=1 -4 CMRR (V/V) 50 -80 VS = 12V VS = 10V -20 -16 -12 -8 -4 0 4 8 12 16 20 OUTPUT VOLTAGE (V) 19973 G21 CMRR vs Temperature 10 GAIN ERROR (m%) GAIN ERROR (ppm) Gain Error vs Temperature 100 -60 VS = 15V 19973 G20 19973 G19 -40 Typical Gain Error for RL = 2k G = 9 (Curves Offset for Clarity) 10 0 -10 -20 -6 -30 -8 -40 -10 -100 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C) VS = 15V 10 UNITS, G=1 -50 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C) 19973 G23 19973 G22 Maximum Power Dissipation vs Temperature Output Voltage vs Load Current 20 5 MAXIMUM POWER DISSIPATION (W) OUTPUT VOLTAGE (V) 15 10 5 130C 85C 25C -45C 0 -5 -10 -15 -20 0 5 10 15 20 25 OUTPUT CURRENT (mA) 30 4 DF14(12) JA = 45C/W 3 2 1 MS16(12) JA = 130C/W 0 -60 -40 -20 0 20 40 60 80 100 120 140 160 AMBIENT TEMPERATURE (C) 19973 G24 19973 G25 19973f For more information www.linear.com/LT1997-3 9 LT1997-3 Typical Performance Characteristics TA = 25C, VS = 15V, Difference Amplifier configuration, unless otherwise noted. Frequency Response vs Capacitive Load (G = 1) Gain vs Frequency 25 GAIN (dB) 15 G=3 10 5 20 20 10 10 0 -10 G=1 0 30 GAIN (dB) G=9 20 30 GAIN (dB) 30 -10 0.001 0.01 0.1 FREQUENCY (MHz) 1 -30 0.001 2 -20 0.01 0.1 1 FREQUENCY (MHz) 40 GAIN (dB) 0 -30 0.001 0pF 0pF 220pF 220pF 560pF 560pF 680pF 680pF 1000pF 1000pF 0.01 0.1 1 FREQUENCY (MHz) 0.1Hz to 10Hz Noise MEASURED IN G = 13 REFERRED TO OP AMP INPUTS 35 25 20 15 10 5 0 1 10 100 1k FREQUENCY (Hz) 10k 100 80 60 40 G=1 G=3 G=9 1k 10k FREQUENCY (Hz) 100k POWER SUPPLY REJECTION RATIO (dB) POWER SUPPLY REJECTION RATIO (dB) 120 20 120 100 80 60 40 G=1 G=3 G=9 20 0 10 19973 G32 10 19973 G31 140 140 100 TIME (10s/DIV) Negative PSRR vs Frequency Positive PSRR vs Frequency 160 10 100k 19973 G30 19973 G29 0 MEASURED IN G = 13 REFERRED TO OP AMP INPUTS 30 10 10 NOISE VOLTAGE (200nV/DIV) VOLTAGE NOISE DENSITY (nV/Hz) 30 10 0.01 0.1 1 FREQUENCY (MHz) 19973 G28 Op Amp Noise Density vs Frequency 20 0pF 0pF 220pF 220pF 560pF 560pF 680pF 680pF 1000pF 1000pF 19973 G27 Frequency Response vs Capacitive Load (G = 9) -20 -30 0.001 10 19973 G26 -10 0 -10 0pF 220pF 560pF 680pF -20 -5 Frequency Response vs Capacitive Load (G = 3) 100 1k 10k FREQUENCY (Hz) 100k 19973 G33 19973f For more information www.linear.com/LT1997-3 LT1997-3 Typical Performance Characteristics TA = 25C, VS = 15V, Difference Amplifier configuration, unless otherwise noted. Slew Rate vs Temperature 2.0 1.8 Large-Signal Step Response G=1 RL = 10k CL = 560pF RL = 10k 1.6 1.2 1.0 0.8 FALLING EDGE 0.6 CL = 680pF 60 VOLTAGE (mV) VOLTAGE (5V/DIV) 1.4 G=1 120 R =10k L 100 80 RISING EDGE 40 20 0 -20 -40 0.4 -60 0.2 -80 -100 0 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C) Small-Signal Step Response 5 10 CL = 1000pF CL = 1000pF 60 VOLTAGE (mV) 20 0 -20 40 20 0 -20 -40 -40 -60 -80 CL = 0pF 0 5 10 -60 CL = 560pF 15 20 25 TIME (s) -80 30 35 -100 40 CL = 0pF 0 5 10 CL = 560pF 15 20 25 TIME (s) 30 19973 G37 35 40 19973 G38 Settling Time Settling Time 5 4 4 4 3 3 3 G=1 2 ERROR VOLTAGE 1 ERROR VOLTAGE (mV) 5 OUTPUT VOLTAGE 2 G=1 6 5 4 3 ERROR VOLTAGE 2 1 1 0 0 -1 -1 -2 -2 -3 -3 0 0 -1 -1 -2 -2 -3 -3 -4 -4 -4 -5 -5 -5 -6 -6 -6 TIME (20s/DIV) OUTPUT VOLTAGE (V) 6 OUTPUT VOLTAGE (V) 6 1 40 CL = 680pF 80 40 2 35 19973 G36 G=9 120 R =10k L 100 60 5 30 Small-Signal Step Response CL = 680pF 80 6 15 20 25 TIME (s) 140 G=3 120 R =10k L 100 VOLTAGE (mV) 0 CL = 560pF 19973 G35 140 -100 CL = 0pF TIME (10s/DIV) 19973 G34 ERROR VOLTAGE (mV) SLEW RATE (V/s) Small-Signal Step Response 140 -4 OUTPUT VOLTAGE -5 -6 TIME (20s/DIV) 19973 G39 19973 G40 19973f For more information www.linear.com/LT1997-3 11 LT1997-3 Typical Performance Characteristics TA = 25C, VS = 15V, Difference Amplifier configuration, unless otherwise noted. Op Amp Offset Voltage vs Temperature Quiescent Current vs Temperature 550 20 UNITS 10 UNITS 500 QUIESCENT CURRENT (A) OP AMP OFFSET VOLTAGE (V) 150 Thermal Shutdown vs Hysteresis 600 100 50 0 -50 -100 500 SUPPLY CURRENT (A) 200 450 400 350 300 250 -200 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) 200 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C) Quiescent Current vs Supply Voltage QUIESCENT CURRENT (A) QUIESCENT CURRENT (A) 50 PARAMETRIC SWEEP IN ~25C TA = 150C INCREMENTS 400 300 TA = -55C 200 100 0 0 10 200 0 145 150 20 30 40 SUPPLY VOLTAGE (V) Shutdown Quiescent Current vs Supply Voltage 150C 125C 85C 40 25C -40C -55C VSHDN = 0V 30 20 10 0 50 0 10 20 30 40 SUPPLY VOLTAGE (V) CHANGE IN OP AMP OFFSET VOLTAGE (V) QUIESCENT CURRENT (A) Minimum Supply Voltage 20 VS = 15V 150C 125C 85C 25C -40C -55C 450 400 350 300 250 200 150 100 50 0 0 5 10 SHDN VOLTAGE (V) 15 15 10 5 TA = 125C 0 -5 TA = 25C -10 -15 -20 TA = -45C 0 19973 G46 12 50 19973 G45 Quiescent Current vs SHDN Voltage 500 170 19973 G43 19973 G44 550 155 160 165 TEMPERATURE (C) 19973 G42 19973 G41 500 300 100 -150 600 400 1 2 3 4 TOTAL SUPPLY VOLTAGE (V) 5 19973 G47 19973f For more information www.linear.com/LT1997-3 LT1997-3 Pin Functions (DFN/MSOP) V+ (Pin 9/Pin 11): Positive Supply Pin. V- (EXPOSED PAD Pin 15/Pin 8): Negative Supply Pin. OUT (Pin 8/Pin 9): Output Pin. +INA (Pin 1/Pin 1): Noninverting Gain-of-1 Input Pin. Connects a 22.5k internal resistor to the internal op amp's noninverting input. +INB (Pin 3/Pin 3): Noninverting Gain-of-3 Input Pin. Connects a 7.5k internal resistor to the internal op amp's noninverting input. +INC (Pin 5/Pin 5): Noninverting Gain-of-9 Input Pin. Connects a 2.5k internal resistor to the internal op amp's noninverting input. -INA (Pin 14/Pin 16): Inverting Gain-of-1 input Pin. Connects a 22.5k internal resistor to the internal op amp's inverting input. -INC (Pin 10/Pin 12): Inverting Gain-of-9 input Pin. Connects a 2.5k internal resistor to the internal op amp's inverting input. REF (Pin 7/NA): Reference Input Pin. Sets the output level when the difference between the inputs is zero. REF1 (NA/Pin 6): Reference 1 Input Pin. With REF2, sets the output level when the difference between the inputs is zero. REF2 (NA/Pin 7): Reference 2 Input. Pin. With REF1, sets the output level when the difference between the inputs is zero. SHDN (Pin 6/Pin 10): Shutdown Pin. Amplifier is active when this pin is tied to V+ or left floating. Pulling the pin >2.5V below V+ causes the amplifier to enter a low power state. -INB (Pin 12/Pin 14): Inverting Gain-of-3 input Pin. Connects a 7.5k internal resistor to the internal op amp's inverting input. Block Diagram MSOP -INA -INB DFN V+ -INC -INA -INB V+ -INC 2.5k 2.5k 22.5k 7.5k 22.5k 7.5k 22.5k 22.5k OUT OUT 22.5k 22.5k 7.5k 2.5k V+ 45k REF1 45k REF2 22.5k 7.5k 2.5k 10A +INA +INB +INC SHDN REF V+ 10A V- +INA +INB 19973 BD01 +INC SHDN V- 19973 BD02 19973f For more information www.linear.com/LT1997-3 13 LT1997-3 Applications Information V-IN op amp (VCMOP) is between V- and V+ - 1.75V, the op amp operates in its normal region; b) If VCMOP is between V+ - 1.75V and V- + 76V, the op amp continues to operate, but in its Over-The-Top (OTT) region with degraded performance (see Over-The-Top Operation section of this data sheet for more detail). VS+ V+ -INA -INB -INC LT1997-3 2.5k 7.5k 22.5k - 22.5k OUT + 22.5k 7.5k 22.5k REF 2.5k +INA +INB +INC SHDN VOUT VREF V- 19973 F01 V+IN VS- Figure 1. Difference Amplifier with Dual-Supply Operation (Gain = 1) Introduction The LT1997-3 is a precision, high voltage general purpose op amp combined with a highly-matched resistor network. It can easily be configured into many different classical gain circuits without adding external components. The several pages of simple circuits in this data sheet demonstrate how easy the LT1997-3 is to use. It can be configured into a difference amplifier (Figure 1), as well as into inverting (Figure 7) and noninverting (Figure 3) single ended amplifiers. The LT1997-3 provides the resistors and op amp together in a small package in order to save board space and reduce complexity. Highly accurate measurement circuits can be easily constructed with the LT1997-3. The circuits can be tailored to specific measurement applications. Common Mode Voltage Range The common mode voltage range of the LT1997-3 is set by the voltage range allowed on the LT1997-3's input pins and by the input voltage range of the internal op amp. The internal op amp of LT1997-3 has 2 operating regions: a) if the common-mode voltage at the inputs of the internal 14 The LT1997-3 will not operate correctly if the commonmode voltage at the inputs of the internal op amp (VCMOP) is below V-, but the part will not be damaged as long as VCMOP is greater than V- - 25V and the junction temperature of the LT1997-3 does not exceed 150C. The allowed voltage range on LT1997-3's input pins are as follows: The voltages at +INA and -INA input pins should never be higher than V- + 160V or lower than V- - 160V under any circumstances; The voltages at +INB, -INB, +INC and -INC input pins should not go below V- - 0.3V or above V- + 80V. The common-mode voltage at the inputs of the internal op amp (VCMOP) is determined by the voltages on pins +INA, +INB, +INC and REF (see the "Calculating Input Voltage Range" section). This condition is true provided that the internal op amp's output is not clipped and feedback maintains the internal op amp's inputs at the same voltage. In addition to the limits mentioned above, the common mode input voltage of the amplifier should be chosen so that the input resistors do not dissipate too much power. The power dissipated in a 22.5k resistor must be less than 1.5W. It must be less than 0.5W for the 7.5k resistor and less than 0.165W for the 2.5k resistor. For most applications, the pin voltage limitations will be reached before the resistor power limitation is reached. Calculating Input Voltage Range Figure 2 shows the LT1997-3 in the generalized case of a difference amplifier, with the inputs shorted for the common mode calculation. The values of RF and RG are dictated by how the positive inputs and REF pin are connected. 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information They are limited by the output swing of the amplifier (and obviously by the allowed voltage range for the input pins). By superposition we can write: VCMOP = VEXT * RG RF + VREF * RF +RG RF +RG Over-The-Top Operation Or, solving for VEXT: R R VEXT = VCMOP * 1+ G - VREF * G RF RF But valid VCMOP voltages are limited to VS+ - 1.75V (VS- + 76V OTT) on the high side and VS- on the low side, so: R R MAX VEXT = ( VS+ -1.75) * 1+ G - VREF * G RF RF and: R R MIN VEXT = ( VS - ) * 1+ G - VREF * G RF RF RF RG VEXT RG - VCMOP VS+ VOUT + VS- 19973 F02 RF VREF Figure 2. Calculating the Common Mode Input Voltage Range Exceeding the MAX VEXT limit will cause the amplifier to transition into the Over-The-Top region. The maximum input voltage for the Over-The-Top region is: R R MAX VEXTOTT = ( VS - +76) * 1+ G - VREF * G RF RF Keep in mind that the above MAX and MIN values for input voltage range should not exceed the allowed voltage range specified earlier for LT1997-3's input pins. The negative inputs are not limited by the internal op amp common mode range (VCMOP) because they do not affect it. When the input common mode voltage of the internal op amp (VCMOP) in the LT1997-3 is biased near or above the V+ supply, the op amp is operating in the Over-The-Top (OTT) region. The op amp continues to operate with an input common mode voltage of up to 76V above V- (regardless of the positive power supply voltage V+), but its performance is degraded. The op amp's input bias currents change from under 2nA to 14A. The op amp's input offset current rises to 50nA, which adds 1.1mV to the output offset voltage. In addition, when operating in the Over-The-Top region, the differential input impedance decreases from 1M in normal operation to approximately 3.7k in Over-The-Top operation. This resistance appears across the summing nodes of the internal op amp and boosts noise and offset while decreasing speed. Noise and offset will increase by between 75% and 450% depending on the gain setting. The bandwidth will be reduced by 2X to 5.5X. For more detail on Over-The-Top operation, consult the LT6015 data sheet. The Classical Noninverting Amplifier: High Input Z A common op amp configuration enabled by the LT1997-3 is the noninverting amplifier. Figure 3 shows the textbook representation of the circuit on the top. The LT1997-3 is shown on the bottom configured in a precision gain of 5.5. One of the benefits of the noninverting op amp configuration is that the input impedance is extremely high. The LT1997-3 maintains this benefit. A large number of gains can be achieved with the LT1997-3 in the noninverting configuration. The complete list of such Hi-Z input noninverting gain configuration is shown in Table 1. Many of these are also represented in Figure 4 in schematic form. Note that the positive inputs are connected such that the source impedance seen by the positive and negative inputs of the internal op amp are equal. This minimizes the offset voltage due to the input bias current of the op amp. The noise gain and amplifier's gain in the noninverting configuration are identical. 19973f For more information www.linear.com/LT1997-3 15 LT1997-3 Applications Information Table 1. Configuring the Negative Pins for Noninverting Gains. The Positive Inputs Are Driven as Shown in the Examples in Figure 4 RF RG VIN RG//RF - + VOUT Negative Input Connections VOUT = GAIN * VIN GAIN = 1 + RF/RG NONINVERTING OP AMP CONFIGURATION VS+ -INA -INB -INC V+ LT1997-3 2.5k 7.5k 22.5k 22.5k - + 22.5k 7.5k OUT 22.5k VOUT REF 2.5k +INA +INB +INC VIN SHDN V- VS- 19973 F03 NONINVERTING OP AMP CONFIGURATION IMPLEMENTED WITH THE LT1997-3, RF = 11.25k, RG = 2.5k, GAIN = 5.5 GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK THE AVAILABLE RESISTORS TO ARRIVE AT THE DESIRED RF AND RG Figure 3. The LT1997-3 Configured as a Noninverting Op Amp 16 Gain -INA -INB -INC 1 VOUT VOUT VOUT 1.077 GND VOUT VOUT 1.1 GND OPEN VOUT 1.25 GND VOUT OPEN 1.273 VOUT GND VOUT 1.3 OPEN GND VOUT 1.4 GND GND VOUT 2 GND OPEN OPEN 2.5 VOUT GND OPEN 2.8 VOUT VOUT GND 3.25 OPEN VOUT GND 3.5 GND VOUT GND 4 OPEN GND OPEN 5 GND GND OPEN 5.5 VOUT OPEN GND 7 VOUT GND GND 10 OPEN OPEN GND 11 GND OPEN GND 13 OPEN GND GND 14 GND GND GND 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information VS+ -INA -INB -INC V+ VS+ LT1997-3 -INA -INB -INC 2.5k 7.5k 22.5k 7.5k 7.5k OUT VOUT 22.5k REF - + 7.5k V- OUT VOUT V S- 22.5k REF V+ 2.5k 22.5k V+ VS+ LT1997-3 -INA -INB -INC 7.5k OUT VOUT 22.5k 7.5k 2.5k 7.5k OUT VOUT V- 22.5k REF 7.5k VS- VIN GAIN = 5.5 VS+ LT1997-3 -INA -INB -INC 2.5k V+ VS+ LT1997-3 -INA -INB -INC 2.5k 7.5k 22.5k 22.5k 7.5k 7.5k OUT VOUT 22.5k 22.5k REF 7.5k 7.5k OUT VOUT V- 22.5k REF 7.5k V S- V- +INA +INB +INC SHDN VS- VIN V+ -INA -INB -INC 7.5k OUT VOUT VIN 22.5k REF - + 7.5k OUT VOUT 22.5k REF 2.5k V- VS- GAIN = 13 LT1997-3 22.5k 22.5k 2.5k +INA +INB +INC SHDN GAIN = 11 V+ 22.5k - + 7.5k V- 2.5k 22.5k 22.5k 22.5k REF VS+ LT1997-3 2.5k 7.5k 22.5k VOUT VS- VIN GAIN = 10 VS+ -INA -INB -INC OUT 2.5k +INA +INB +INC SHDN GAIN = 7 - + 22.5k 2.5k +INA +INB +INC SHDN LT1997-3 22.5k 22.5k - + 22.5k 2.5k V+ 2.5k 22.5k - + 22.5k VOUT 22.5k REF V- +INA +INB +INC SHDN GAIN = 5 VS+ V+ V- VS- VIN GAIN = 4 OUT 2.5k +INA +INB +INC SHDN V S- - + 22.5k 2.5k +INA +INB +INC SHDN LT1997-3 22.5k 22.5k - + 22.5k 22.5k REF V+ 2.5k 7.5k 22.5k - + 22.5k 22.5k REF GAIN = 3.25 2.5k 22.5k VOUT VS- VIN VS+ -INA -INB -INC OUT V- +INA +INB +INC SHDN GAIN = 2 LT1997-3 7.5k - + 7.5k VS- VIN 22.5k 22.5k V- +INA +INB +INC SHDN GAIN = 1 LT1997-3 2.5k VS+ VIN 7.5k 22.5k 2.5k +INA +INB +INC SHDN -INA -INB -INC -INA -INB -INC 22.5k 22.5k 2.5k VIN LT1997-3 V+ 2.5k 22.5k - + 22.5k -INA -INB -INC VS+ 2.5k 22.5k VIN V+ +INA +INB +INC SHDN VIN V- VS- 19973 F04 GAIN = 14 Figure 4. Some Implementations of Classical Noninverting Gains Using the LT1997-3. High Input Z is Maintained 19973f For more information www.linear.com/LT1997-3 17 LT1997-3 Applications Information Attenuation Table 2. Configuring the Positive Pins for Various Attenuations The positive input resistors can be configured to attenuate the input signal (Figure 5). This allows a trade-off to be made between input range and precision. Attenuating the input can prevent the op amp from entering the less precise Over-the-Top operating region at the cost of decreasing the output signal. The four positive resistors (R+INA, R+INB, R+INC, RREF) can be arranged to make many precise input attenuators. These are shown in Table 2. LT1997-3 VIN RA 7.5k VCMOP = A * VIN A = RG/(RA + RG) 22.5k +INB +INC REF VIN GND GND GND 0.0769 VIN GND GND OPEN 0.0909 VIN OPEN GND GND 0.1 VIN OPEN GND OPEN 0.143 VIN GND GND VIN 0.182 VIN OPEN GND VIN 0.2 VIN GND OPEN GND 0.214 GND VIN GND GND 0.231 OPEN VIN GND GND OPEN VIN GND OPEN 0.286 VIN VIN GND GND +INA +INB +INC 0.308 VIN VIN GND OPEN 0.357 VIN VIN GND VIN 0.4 VIN GND OPEN VIN 0.5 VIN OPEN OPEN GND REF 19973 F05 ATTENUATING THE POSITIVE INPUT BY GROUNDING AN UNUSED INPUT RA = 22.5k, RG = 2.5k, A = 0.1 Figure 5. The Input of the LT1997-3 Can Be Attenuated to Increase the Usable Input Range. The +INA Input Can Be Taken to 160V. The attenuations and noninverting gains are set independently and can be combined to produce even more gain options. 346 unique gains between 0.0714 and 14 (Figure 6) can be realized. When using the positive side resistors as an attenuator, the benefit of canceling input bias current effects on offset voltage reduces. The impedance seen by the two op amp input nodes will not be identical. 100 10 GAIN +INA 0.25 VIN UP TO +160V ATTENUATOR Gain 0.0714 2.5k VCMOP RG - + 22.5k Positive Input Connections 0.6 GND VIN OPEN GND 0.643 GND GND VIN GND 0.692 OPEN GND VIN GND 0.714 VIN GND VIN GND 0.75 OPEN VIN OPEN GND 0.769 VIN GND VIN OPEN 0.786 VIN GND VIN VIN 0.8 VIN VIN OPEN GND 0.818 GND OPEN VIN GND 0.857 GND VIN VIN GND 0.9 OPEN OPEN VIN GND 0.909 VIN OPEN VIN GND 0.923 OPEN VIN VIN GND 0.929 VIN VIN VIN GND 1 VIN VIN VIN VIN 1 0.1 0.01 0 50 100 150 200 COUNT 250 300 350 19973 F06 Figure 6. Many Unique Gains Can Be Achieved by Combining Attenuation with Noninverting Gain 18 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information The Inverting Configuration Table 3. Configuring the Negative Pins for Inverting Gains The inverting amplifier, shown in Figure 7, is another classical op amp configuration. The circuit is actually identical to the noninverting amplifier of Figure 3, except that VIN and GND have been swapped. The list of available gains is shown in Table 3, and some of the circuits are shown in Figure 8. Noise gain is 1+|Gain|, as is the usual case for inverting amplifiers. For the best DC precision, match the source impedances seen by the op amp inputs. RF VIN RG RG//RF - + VOUT VOUT = GAIN * VIN GAIN = -RF/RG INVERTING OP AMP CONFIGURATION VIN VS+ -INA -INB -INC V+ LT1997-3 2.5k 7.5k 22.5k 22.5k - + 22.5k 7.5k OUT 22.5k VOUT Negative Input Connections Gain -INA -INB -INC -0.077 VIN VOUT VOUT -0.1 VIN OPEN VOUT -0.25 VIN VOUT OPEN -0.273 VOUT VIN VOUT -0.3 OPEN VIN VOUT -0.4 VIN VIN VOUT -1 VIN OPEN OPEN -1.5 VOUT VIN OPEN -1.8 VOUT VOUT VIN -2.25 OPEN VOUT VIN -2.5 VIN VOUT VIN -3 OPEN VIN OPEN -4 VIN VIN OPEN -4.5 VOUT OPEN VIN -6 VOUT VIN VIN -9 OPEN OPEN VIN -10 VIN OPEN VIN -12 OPEN VIN VIN -13 VIN VIN VIN REF 2.5k +INA +INB +INC SHDN V- VS- 19973 F07 INVERTING OP AMP CONFIGURATION IMPLEMENTED WITH THE LT1997-3, RF = 11.25k, RG = 2.5k, GAIN = -4.5 GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK THE AVAILABLE RESISTORS TO ARRIVE AT THE DESIRED RF AND RG Figure 7. The LT1997-3 Configured as an Inverting Op Amp 19973f For more information www.linear.com/LT1997-3 19 LT1997-3 Applications Information VS+ VIN -INA -INB -INC V+ VS+ VIN LT1997-3 -INA -INB -INC 2.5k V+ 22.5k 22.5k 7.5k OUT VOUT 22.5k 7.5k 2.5k 7.5k OUT VOUT V- 22.5k REF 7.5k V S- V- VS- VS+ VS- GAIN = -2.25 VS+ VIN LT1997-3 -INA -INB -INC 2.5k V+ VS+ VIN LT1997-3 -INA -INB -INC 2.5k 7.5k 22.5k 22.5k 7.5k OUT VOUT 22.5k 7.5k 2.5k 7.5k OUT VOUT V- 22.5k REF 7.5k V S- V- VS- VS+ VS- GAIN = -4.5 VS+ VIN LT1997-3 -INA -INB -INC 2.5k V+ VS+ VIN LT1997-3 -INA -INB -INC 2.5k 7.5k 22.5k 22.5k 7.5k OUT VOUT 22.5k 7.5k 2.5k 7.5k OUT VOUT V- 22.5k REF 7.5k V- +INA +INB +INC SHDN VS- GAIN = -6 VS+ -INA -INB -INC V+ VS+ -INA -INB -INC 2.5k 22.5k 7.5k 7.5k LT1997-3 22.5k 22.5k - + 22.5k V+ 2.5k 7.5k 22.5k V- GAIN = -10 VIN LT1997-3 VOUT 22.5k REF VS- GAIN = -9 VIN OUT 2.5k +INA +INB +INC SHDN V S- - + 22.5k 2.5k +INA +INB +INC SHDN LT1997-3 22.5k 22.5k - + 22.5k 22.5k REF V+ 2.5k 7.5k 22.5k - + 22.5k VOUT 22.5k REF V- +INA +INB +INC SHDN GAIN = -4 V+ OUT 2.5k +INA +INB +INC SHDN GAIN = -3 VIN - + 22.5k 2.5k +INA +INB +INC SHDN LT1997-3 22.5k 22.5k - + 22.5k 22.5k REF V+ 2.5k 7.5k 22.5k - + 22.5k VOUT 22.5k REF V- +INA +INB +INC SHDN GAIN = -1 V+ OUT 2.5k +INA +INB +INC SHDN GAIN = -0.25 VIN - + 22.5k 2.5k +INA +INB +INC SHDN LT1997-3 22.5k 22.5k - + 22.5k 22.5k REF V+ 2.5k 7.5k 22.5k - + 22.5k -INA -INB -INC -INA -INB -INC 2.5k 7.5k -INA -INB -INC VS+ VIN LT1997-3 OUT 22.5k REF 2.5k VOUT - + 22.5k 7.5k OUT VOUT 22.5k REF 2.5k V- +INA +INB +INC SHDN +INA +INB +INC SHDN VS- GAIN = -12 V- VS- 19973 F08 GAIN = -13 Figure 8. Inverting Gains with Input Impedance that Varies from 1.73k (Gain = -13) to 22.5k (Gain = -1) 20 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information Difference Amplifiers The LT1997-3 is ideally suited to be used as a difference amplifier. Figure 9 shows the basic 4-resistor difference amplifier and the LT1997-3. A difference gain of 3 is shown, but can be altered by additional dashed connections. By connecting the 22.5k resistors in parallel, the gain is reduced by a factor of 2. Of course there are many possible gains. Table 4 shows the difference gains and how they are achieved. Note that, as for inverting amplifiers, the noise gain is equal to the signal gain plus 1. RF V-IN V+IN - + RG RG VOUT VOUT = GAIN * (V+IN - V-IN) GAIN = RF/RG RF DIFFERENCE AMPLIFIER CONFIGURATION VS+ V-IN -INA -INB -INC V+ LT1997-3 2.5k 7.5k 22.5k 22.5k - + 22.5k 7.5k OUT 22.5k VOUT REF The Common Mode Voltage at the inputs of the internal op amp (VCMOP) is set by the voltages at pins +INA, +INB, +INC and REF. Table 4. Difference Amplifier Gains Gain V+IN V-IN OUT GND (REF) 0.077 +INA -INA -INB, -INC +INB, +INC 0.1 +INA -INA -INC +INC 0.25 +INA -INA -INB +INB 0.273 +INB -INB -INA, -INC +INA, +INC 0.3 +INB -INB -INC +INC 0.4 +INA, +INB -INA, -INB -INC +INC 1 +INA -INA 1.5 +INB -INB -INA +INA 1.8 +INC -INC -INA, -INB +INA, +INB 2.25 +INC -INC -INB +INB 2.5 +INA, +INC -INA, -INC -INB +INB 3 +INB -INB 4 +INA, +INB -INA, -INB 4.5 +INC -INC -INA +INA 6 +INB, +INC -INB, -INC -INA +INA 9 +INC -INC 10 +INA, +INC -INA, -INC 12 +INB, +INC -INB, -INC 13 +INA, +INB, +INC -INA, -INB, -INC 2.5k +INA +INB +INC V+IN SHDN V- VS- 19973 F09 DIFFERENCE AMPLIFIER CONFIGURATION IMPLEMENTED WITH THE LT1997-3, RF = 22.5k, RG = 7.5k, GAIN = 3 ADDING THE DASHED CONNECTIONS CONNECT THE TWO 22.5k RESISTORS IN PARALLEL, SO RF IS REDUCED TO 11.25k. THE GAIN BECOMES 11.25k/7.5k = 1.5 Figure 9. The LT1997-3 Configured as a Difference Amplifier. Gain Is Set by Connecting the Correct Resistors or Combinations of Resistors. Gain of 3 Is Shown, with Dashed Lines Modifying It to a Gain of 1.5 19973f For more information www.linear.com/LT1997-3 21 LT1997-3 Applications Information VS+ V-IN -INA -INB -INC V+ VS+ V-IN LT1997-3 -INA -INB -INC 2.5k 7.5k 22.5k LT1997-3 -INA -INB -INC 7.5k 7.5k OUT VOUT 22.5k 22.5k REF 7.5k 7.5k OUT VOUT V- 22.5k REF 7.5k V+ VS- V+IN VS+ -INA -INB -INC 2.5k V+ VS+ V-IN LT1997-3 -INA -INB -INC 2.5k 7.5k 22.5k 22.5k 7.5k OUT VOUT 22.5k 7.5k 2.5k 7.5k OUT VOUT V- +INA +INB +INC SHDN 22.5k REF 7.5k V+ VS- GAIN = 4.5 VS+ V-IN LT1997-3 -INA -INB -INC 2.5k V+ VS+ V-IN LT1997-3 -INA -INB -INC 2.5k 7.5k 22.5k 22.5k 7.5k OUT VOUT 22.5k 7.5k 2.5k 7.5k OUT VOUT V- 22.5k REF 7.5k V- +INA +INB +INC SHDN VS- V+IN GAIN = 6 VS+ -INA -INB -INC V+ VOUT 22.5k REF V- VS- V+IN GAIN = 9 V-IN OUT 2.5k +INA +INB +INC SHDN VS- V+IN - + 22.5k 2.5k +INA +INB +INC SHDN LT1997-3 22.5k 22.5k - + 22.5k 22.5k REF V+ 2.5k 7.5k 22.5k - + 22.5k VOUT 22.5k REF V- +INA +INB +INC SHDN V+IN GAIN = 4 VS+ V-IN V- VS- V+IN GAIN = 3 OUT 2.5k +INA +INB +INC SHDN VS- - + 22.5k 2.5k V+IN LT1997-3 22.5k 22.5k - + 22.5k 22.5k REF V+ 2.5k 7.5k 22.5k - + 22.5k 22.5k REF GAIN = 2.25 V-IN LT1997-3 VOUT V- +INA +INB +INC SHDN GAIN = 1 VS+ V-IN V- VS- V+IN GAIN = 0.25 OUT 2.5k +INA +INB +INC SHDN VS- V+IN - + 22.5k 2.5k +INA +INB +INC SHDN LT1997-3 22.5k 22.5k - + 22.5k 2.5k V+ 2.5k 22.5k - + 22.5k -INA -INB -INC VS+ V-IN 2.5k 22.5k -INA -INB -INC V+ GAIN = 10 V-IN LT1997-3 VS+ -INA -INB -INC 2.5k V+ LT1997-3 2.5k 7.5k 22.5k 22.5k 7.5k 22.5k 22.5k - + 22.5k 7.5k OUT VOUT - + 22.5k 22.5k REF 7.5k 2.5k OUT VOUT 22.5k REF 2.5k +INA +INB +INC SHDN V- VS- V+IN GAIN = 12 +INA +INB +INC SHDN V- VS- V+IN 19973 F10 GAIN = 13 Figure 10. Many Difference Amplifier Gains Can Be Achieved by Strapping Pins 22 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information Difference Amplifier: Additional Integer Gains Using Cross-Coupling RF Figure 11 shows the basic difference amplifier as well as the LT1997-3 with cross-coupled inputs. The additional dashed connections reduce the differential gain from 3 to 2. Using this method, additional integer gains are achievable, as shown in Table 5, so that all integer gains from 1 to 13 are achieved with the LT1997-3. Note that the equations can be written by inspection from the V+IN connections, and that the V-IN connections are simply the opposite (swap + for - and - for +). Noise gain, bandwidth, and input impedance specifications for the various cases are also shown. Schematics of the difference amplifiers using cross-coupling are shown in Figure 12. Additional non-integer gains produced with cross-coupling are listed in Table 6. - + RG V-IN RG V+IN VOUT VOUT = GAIN * (V+IN - V-IN) GAIN = RF/RG RF DIFFERENCE AMPLIFIER CONFIGURATION V-IN VS+ V+ -INA -INB -INC LT1997-3 2.5k 7.5k 22.5k 22.5k - + 22.5k 7.5k OUT 22.5k VOUT REF 2.5k +INA +INB +INC SHDN V- 19973 F12 VS- V+IN DIFFERENCE AMPLIFIER CONFIGURATION IMPLEMENTED WITH THE LT1997-3, RF = 22.5k, RG = 7.5k, GAIN = 3 GAIN CAN BE ADJUSTED BY CROSS-COUPLING THE INPUTS. MAKING THE DASHED CONNECTIONS REDUCES THE GAIN FROM 3 TO 2 Figure 11. Cross-Coupling the Inputs of the LT1997-3 Allows Additional Integer Gains to Be Constructed. The LT1997-3 Provides All Integer Gains from 1 to 13 Table 5. Connections Using Cross-Coupling. Note that Equations Can Be Written by Inspection of the V+IN Column Gain V+IN V-IN Equation Noise Gain -3dB BW (kHz) Differential Input Impedance (k) Common Mode Input Impedance (k) 2 +INB, -INA -INB, +INA 3-1 5 540 11.25 14.1 5 +INC, -INB, -INA -INC, +INB, +INA 9-3-1 14 222 3.5 12.1 7 +INC, +INA, -INB -INC, -INA, +INB 9+1-3 14 222 3.5 12.1 8 +INC, -INA -INC, +INA 9-1 11 277 4.5 12.4 11 +INC, +INB, -INA -INC, -INB, +INA 9+3-1 14 222 3.5 12.1 Table 6. Additional Non-Integer Gains that Can Be Achieved Using Cross-Coupling Gain V+IN V-IN OUT GND (REF) 0.143 +INA -INA +INB, -INC -INB, +INC 0.2 -INA, +INB +INA, -INB -INC +INC 0.333 +INB -INB +INA, -INC -INA, +INC 19973f For more information www.linear.com/LT1997-3 23 LT1997-3 Applications Information V-IN V-IN VS+ V+ -INA -INB -INC LT1997-3 -INA -INB -INC 2.5k VS+ LT1997-3 -INA -INB -INC 2.5k 7.5k 22.5k 22.5k 7.5k OUT VOUT 22.5k 7.5k 2.5k 7.5k OUT VOUT V- 22.5k REF 7.5k VS- V- +INA +INB +INC SHDN VS- V+IN V+ -INA -INB -INC VS+ V+ -INA -INB -INC LT1997-3 2.5k LT1997-3 2.5k 7.5k 22.5k 22.5k 7.5k 7.5k 22.5k 22.5k - + 22.5k OUT VOUT - + 22.5k 22.5k REF 7.5k 2.5k OUT VOUT 22.5k REF 2.5k +INA +INB +INC SHDN V+IN V- GAIN = 7 V-IN VS+ VOUT 22.5k REF VS- V+IN GAIN = 5 V-IN OUT 2.5k +INA +INB +INC SHDN GAIN = 2 - + 22.5k 2.5k +INA +INB +INC SHDN LT1997-3 22.5k 22.5k - + 22.5k 22.5k REF V+ 2.5k 7.5k 22.5k - + 22.5k V+IN V-IN VS+ V+ V- VS- GAIN = 8 +INA +INB +INC SHDN V- 19973 F13 VS- V+IN GAIN = 11 Figure 12. Integer Gain Difference Amplifiers Using Cross-Coupling High Common Mode Voltage Difference Amplifiers The input range of a difference amplifier can be extended by configuring the amplifier to divide the input common mode voltage. Figure 13 shows the basic circuit on the top. The effective input voltage range of the circuit is extended by the fact that resistors RT attenuate the common mode (CM) voltage seen by the internal op amp inputs (VCMOP). For the LT1997-3, the most useful resistors for RG are the +INA and -INA 22.5k resistors, because they do not have diode clamps to the VS- supply and therefore can be taken beyond both rails. +INB, -INB, +INC and -INC pins can be taken 80V above VS-, but not below VS-. As before, the input common mode of the internal op amp is the limiting factor and is set by the voltage at the op amp's positive input (VCMOP). By superposition we can write: VCMOP = VEXT * RG RT RF RT + VREF * RG +RF RT RF +RG RT +VTERM * RF RG RT +RF RG Solving for VEXT: VEXT RG RT VCMOP - VREF * RF +RG RT RG = 1+ * RF RG RF RT -V TERM * RT +RF RG 24 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information Given the values of the resistors in the LT1997-3, this equation has been simplified and evaluated, and the resulting equations are provided in Table 7. Substituting VS+ - 1.75V and VS - for VLIM will give the valid upper and lower common mode extremes respectively for the normal operating region of the op amp. Substituting VS - + 76V and VS - for VLIM will give the valid upper and lower common mode extremes respectively for the Over-The-Top region of the op amp (see Over-The-Top Operation section of this data sheet for more detail). Following are sample calculations for the case shown in Figure 13. Note that +INC and -INC are terminated so row 3 of Table 7 provides the equation: RF V-IN V+IN (= VEXT) RG - RG VCMOP RT VS+ VOUT + RT VS- VTERM VOUT = GAIN * (V+IN - V-IN) GAIN = RF/RG RF VREF HIGH COMMON MODE VOLTAGE DIFFERENCE AMPLIFIER INPUT COMMON MODE VOLTAGE TO OP AMP IS ATTENUATED BY RESISTORS RT CONNECTED TO VTERM V-IN VS+ = 12V -INA -INB -INC MAX VEXT = 11* ( VS+ -1.75) - VREF - 9 * VTERM V+ LT1997-3 2.5k 7.5k = 11* (10.25V) - 2.5 - 9 * 12 22.5k 22.5k = 2.25V VTERM = 12V - + 22.5k 7.5k and: OUT 22.5k REF 2.5k MIN VEXT = 11* ( VS - ) - VREF - 9 * VTERM = 11* (0) - 2.5 - 9 * 12 +INA +INB +INC = -110.5V SHDN V- VOUT VREF = 2.5V 19973 F14 V+IN HIGH NEGATIVE COMMON MODE VOLTAGE DIFFERENCE AMPLIFIER IMPLEMENTED WITH THE LT1997-3, RF = 22.5k, RG = 22.5k, RT = 2.5k, GAIN = 1 If the calculated VEXT voltage exceeds the 160V absolute maximum rating of the +INA, -INA pins, 160V or -160V would become the de facto common mode limit. Several more examples of high CM circuits are shown in Figure 14, Figure 15 and Figure 16 for various supplies. VTERM = VS+ = 12V, VREF = 2.5V, VS- = 0V Figure 13. Extending Common Mode Input Range Table 7. Input Common Mode Voltage Ranges for the LT1997-3 when Configured as a High Common Mode Voltage Difference Amplifier RT Noise Gain Max, Min VEXT (Substitute VS+ - 1.75 (Normal Region) or VS- + 76 (OTT), and VS- for VLIM) 2 2 * VLIM - VREF Gain V+IN V-IN 1 +INA -INA 1 +INA -INA R+INB, R-INB 5 5 * VLIM - VREF - 3 * VTERM 1 +INA -INA R+INC, R-INC 11 11 * VLIM - VREF - 9 * VTERM 1 +INA -INA R+INB||R+INC, R-INB||R-INC 14 14 * VLIM - VREF - 12 * VTERM 19973f For more information www.linear.com/LT1997-3 25 LT1997-3 Applications Information 5V V-IN -INA -INB -INC V+ 5V V-IN -INA -INB -INC LT1997-3 2.5k 22.5k - + 22.5k 7.5k OUT 22.5k REF VOUT 7.5k 2.5V +INA +INB +INC 2.5V OUT VOUT 5V 22.5k REF 7.5k SHDN V- +INA +INB +INC -INA -INB -INC 22.5k - + 22.5k 7.5k 22.5k REF 2.5k +INA +INB +INC VOUT 2.5V +INA +INB +INC OUT 22.5k REF VOUT 2.5k +INA +INB +INC 22.5k 22.5k - + 22.5k 7.5k OUT 22.5k REF 2.5k +INA +INB +INC VOUT 2.5V SHDN V- +INA +INB +INC -INA -INB -INC V+ -INA -INB -INC LT1997-3 22.5k - + 22.5k 7.5k V+ OUT 22.5k REF VOUT 7.5k 2.5V 2.5V +INA +INB +INC +INA +INB +INC VCM = 13V TO -32.5V 2.5V SHDN V- 5V 5V 5V -INA -INB -INC LT1997-3 V+ 7.5k LT1997-3 22.5k 22.5k OUT 22.5k REF VOUT 7.5k OUT 22.5k REF 2.5k SHDN V- +INA +INB +INC V+IN VCM = 43V TO -2.5V - + 22.5k 2.5V V+IN 2.5V VOUT VCM = -11.75V TO -47.5V V-IN 2.5k SHDN V- 22.5k REF 2.5k - + 7.5k OUT 2.5k 22.5k 22.5k - + 22.5k SHDN V- 7.5k 22.5k 2.5k +INA +INB +INC 22.5k REF VOUT 2.5k 7.5k 22.5k OUT 5V 2.5k LT1997-3 22.5k 22.5k V+IN V-IN V+ 7.5k VCM = 33.25V TO -2.5V 5V SHDN V- 5V -INA -INB -INC V+IN 2.5V 2.5V 5V V-IN LT1997-3 2.5k VCM = 10.75V TO -25V V-IN - + 7.5k 2.5V VCM = -1.25V TO -17.5V 22.5k 22.5k VOUT 2.5k 7.5k 22.5k 22.5k REF 5V 2.5k 7.5k OUT 2.5k SHDN V- V+ - + 7.5k 2.5V 5V -INA -INB -INC LT1997-3 22.5k 22.5k V+IN V-IN LT1997-3 V+ 7.5k VCM = 13.75V TO -2.5V 5V V+ SHDN V- 5V 22.5k V+IN -INA -INB -INC 5V -INA -INB -INC LT1997-3 2.5k SHDN V- 5V 2.5k - + 7.5k VCM = 6.25V TO -10V V+IN V-IN 22.5k 22.5k 2.5V 2.5V V-IN V+ 7.5k 22.5k OUT VOUT VCM = 1.5V TO -5V 2.5k 7.5k 22.5k REF 2.5k 5V 2.5k 22.5k OUT V+IN V-IN LT1997-3 - + 22.5k VCM = 6.5V TO 0V V+ LT1997-3 22.5k 22.5k 2.5k SHDN V- V+ 7.5k V+IN -INA -INB -INC V+IN - + 22.5k VCM = 4V TO -2.5V V+IN 22.5k 22.5k V+IN V-IN -INA -INB -INC 2.5k 7.5k 2.5k +INA +INB +INC 5V V-IN LT1997-3 2.5k 7.5k 22.5k V+ SHDN V- VOUT 2.5V 19973 F15 5V VCM = -17V TO -62.5V Figure 14. Common Mode Ranges for Various LT1997-3 Configurations on VS = 5V, 0V, with Gain = 1. These Ranges Guarantee that the Internal Op Amp Operates in Its Normal Operating Region 26 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information 15V V-IN -INA -INB -INC V+ 15V V-IN -INA -INB -INC LT1997-3 2.5k 22.5k - + 22.5k 7.5k +INA +INB +INC OUT VOUT 7.5k SHDN V- +INA +INB +INC V+IN V+ V-IN 22.5k - + 7.5k V+IN OUT VOUT 22.5k REF SHDN V- +INA +INB +INC V+IN -15V V+ -15V V-IN -INA -INB -INC - + OUT VOUT 22.5k REF 7.5k +INA +INB +INC +INA +INB +INC V+IN -15V -15V VCM = 145.75V TO -160V -INA -INB -INC -15V V+ -INA -INB -INC LT1997-3 22.5k - + 22.5k 7.5k OUT VOUT V+IN V+IN 15V 22.5k REF -15V VCM = 160V TO -160V +INA +INB +INC V+IN SHDN V- -15V 15V V-IN -INA -INB -INC LT1997-3 15V V+ 7.5k LT1997-3 22.5k 22.5k OUT VOUT - + 22.5k 22.5k REF 7.5k OUT VOUT 22.5k REF 2.5k SHDN V- +INA +INB +INC V+IN -15V 15V V+ SHDN V- -15V VCM = 10.75V TO -160V 15V 15V V-IN -INA -INB -INC LT1997-3 V+ LT1997-3 2.5k 7.5k 22.5k 22.5k OUT VOUT - + 22.5k 22.5k REF 7.5k 2.5k SHDN V- VOUT 22.5k REF 2.5k - + 7.5k OUT VCM = 21.25V TO -120V 22.5k 22.5k 2.5k +INA +INB +INC +INA +INB +INC 15V V+ 7.5k 22.5k - + 7.5k 2.5k 7.5k LT1997-3 22.5k 22.5k 22.5k REF 15V V-IN 2.5k 22.5k VOUT VCM = 160V TO -30V 15V V-IN OUT 2.5k SHDN V- V+ 7.5k SHDN V- - + 22.5k SHDN V- 15V 22.5k 22.5k 22.5k 15V 2.5k 7.5k 2.5k V+IN 15V -INA -INB -INC LT1997-3 VOUT -15V VCM = 11.5V TO -45V 2.5k 22.5k 7.5k V-IN -15V 2.5k 7.5k 22.5k +INA +INB +INC V+IN VCM = 111.25V TO -30V LT1997-3 22.5k REF 2.5k 2.5k 15V 22.5k -15V OUT 2.5k - + 7.5k -15V -INA -INB -INC 7.5k 22.5k 22.5k VCM = 66.25V TO -75V V-IN V+ - + 22.5k SHDN V- 7.5k 22.5k 2.5k +INA +INB +INC 22.5k REF VOUT 2.5k 7.5k 22.5k OUT 15V -INA -INB -INC LT1997-3 LT1997-3 22.5k 22.5k -15V VCM = 41.5V TO -15V -15V V+ 7.5k 2.5k 2.5k 22.5k - + 22.5k 22.5k REF 15V -INA -INB -INC 22.5k 22.5k -15V VCM = 26.5V TO -30V V-IN -INA -INB -INC 2.5k 7.5k 2.5k V+IN 15V V-IN LT1997-3 2.5k 7.5k 22.5k V+ OUT VOUT 22.5k REF 2.5k SHDN V- -15V -15V VCM = 160V TO -30V +INA +INB +INC V+IN 15V SHDN V- 19973 F16 -15V VCM = 5.5V TO -160V Figure 15. Common Mode Ranges for Various LT1997-3 Configurations on VS = 15V, with Gain = 1. These Ranges Guarantee that the Internal Op Amp Operates in Its Normal Operating Region 19973f For more information www.linear.com/LT1997-3 27 LT1997-3 Applications Information 25V V-IN -INA -INB -INC V+ 25V V-IN -INA -INB -INC LT1997-3 2.5k 22.5k - + 22.5k 7.5k +INA +INB +INC OUT VOUT 7.5k SHDN V- +INA +INB +INC V+IN V+ V-IN 22.5k - + 7.5k V+IN OUT VOUT 22.5k REF SHDN V- +INA +INB +INC V+IN -25V V+ -25V V-IN -INA -INB -INC - + OUT VOUT 22.5k REF 7.5k +INA +INB +INC +INA +INB +INC V+IN -25V -25V VCM = 160V TO -160V -INA -INB -INC -25V V+ -INA -INB -INC LT1997-3 22.5k - + 22.5k 7.5k OUT VOUT V+IN V+IN 25V 22.5k REF -25V VCM = 160V TO -160V +INA +INB +INC V+IN SHDN V- -25V 25V V-IN -INA -INB -INC LT1997-3 25V V+ 7.5k LT1997-3 22.5k 22.5k OUT VOUT - + 22.5k 22.5k REF 7.5k OUT VOUT 22.5k REF 2.5k SHDN V- +INA +INB +INC V+IN -25V 25V V+ SHDN V- -25V VCM = 30.75V TO -160V 25V 25V V-IN -INA -INB -INC LT1997-3 V+ LT1997-3 2.5k 7.5k 22.5k 22.5k OUT VOUT - + 22.5k 22.5k REF 7.5k 2.5k SHDN V- VOUT 22.5k REF 2.5k - + 7.5k OUT VCM = 41.25V TO -160V 22.5k 22.5k 2.5k +INA +INB +INC +INA +INB +INC 25V V+ 7.5k 22.5k - + 7.5k 2.5k 7.5k LT1997-3 22.5k 22.5k 22.5k REF 25V V-IN 2.5k 22.5k VOUT VCM = 160V TO -50V 25V V-IN OUT 2.5k SHDN V- V+ 7.5k SHDN V- - + 22.5k SHDN V- 25V 22.5k 22.5k 22.5k 25V 2.5k 7.5k 2.5k V+IN 25V -INA -INB -INC LT1997-3 VOUT -25V VCM = 21.5V TO -75V 2.5k 22.5k 7.5k V-IN -25V 2.5k 7.5k 22.5k +INA +INB +INC V+IN VCM = 160V TO -50V LT1997-3 22.5k REF 2.5k 2.5k 25V 22.5k -25V OUT 2.5k - + 7.5k -25V -INA -INB -INC 7.5k 22.5k 22.5k VCM = 116.25V TO -125V V-IN V+ - + 22.5k SHDN V- 7.5k 22.5k 2.5k +INA +INB +INC 22.5k REF VOUT 2.5k 7.5k 22.5k OUT 25V -INA -INB -INC LT1997-3 LT1997-3 22.5k 22.5k -25V VCM = 71.5V TO -25V -25V V+ 7.5k 2.5k 2.5k 22.5k - + 22.5k 22.5k REF 25V -INA -INB -INC 22.5k 22.5k -25V VCM = 46.5V TO -50V V-IN -INA -INB -INC 2.5k 7.5k 2.5k V+IN 25V V-IN LT1997-3 2.5k 7.5k 22.5k V+ OUT VOUT 22.5k REF 2.5k SHDN V- -25V -25V VCM = 160V TO -50V +INA +INB +INC V+IN SHDN V- 19973 F17 -25V 25V VCM = 25.5V TO -160V Figure 16. Common Mode Ranges for Various LT1997-3 Configurations on VS = 25V, with Gain = 1. These Ranges Guarantee that the Internal Op Amp Operates in Its Normal Operating Region 28 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information Reference Resistors In the preceding discussions, the Reference resistor is shown as a single 22.5k resistor. This is true in the DFN package. In the MSOP package the reference resistor is split into two 45k resistors (Figure 17). Tying the REF1 and REF2 pins to the same voltage produces the same reference voltage as tying the VREF pin in the DFN package to that voltage. Connecting REF1 and REF2 to different voltages produces an effective reference voltage that is the average of VREF1 and VREF2. This is especially useful when the desired reference voltage is half way between the supplies. Tying REF1 to VS+ and REF2 to VS- produces the desired mid-supply voltage without the help of another external reference voltage (Figure 17). The ratio of RREF1 to RREF2 is very precise: R R -R = REF1 REF2 < 60ppm R +R R REF1 REF2 2 VS+ V-IN -INA -INB -INC V+ LT1997-3 2.5k 7.5k 22.5k 22.5k - + 22.5k 7.5k OUT 45k REF1 45k REF2 2.5k +INA +INB +INC VOUT VREF1 VREF2 SHDN V- VS- V+IN LT1997-3 MSOP VS+ V-IN -INA -INB -INC V+ LT1997-3 2.5k 7.5k 22.5k 22.5k - + 22.5k 7.5k OUT 22.5k 2.5k +INA +INB +INC REF VOUT VREF SHDN V- V+IN VS- LT1997-3 DFN 19973 F11 Figure 17. The LT1997-3 Reference Resistors: Split Resistors in the MSOP Package Above, Single Resistor in the DFN Package Below 19973f For more information www.linear.com/LT1997-3 29 LT1997-3 Applications Information Shutdown Power Dissipation Considerations The LT1997-3 has a shutdown pin (SHDN). Under normal operation this pin should be tied to V+ or allowed to float. Tying this pin 2.5V or more below V+ will cause the part to enter a low power state. The supply current is reduced to less than 25A and the op amp output becomes high impedance. The voltages at the input pins can be still be present even in shutdown mode. Because of the ability of the LT1997-3 to operate on power supplies up to 25V, to withstand very high input voltages and to drive heavy loads, there is a need to ensure the die junction temperature does not exceed 150C. The LT1997-3 is housed in DF14 (JA = 45C/W, JC = 3C/W) and MS16 (JA = 130C/W) packages. Supply Voltage The positive supply pin of the LT1997-3 should be bypassed with a small capacitor (typically 0.1F) as close to the supply pins as possible. When driving heavy loads, an additional 4.7F electrolytic capacitor should be added. When using split supplies, the same is true for the V- supply pin. Output The output of the LT1997-3 can typically swing to within 100mV of either rail with no load and is capable of sourcing and sinking approximately 25mA at 25C. The LT1997-3 is internally compensated to drive at least 1nF of capacitance under any output loading conditions. For larger capacitive loads, a 0.22F capacitor in series with a 150 resistor between the output and ground will compensate the amplifier to drive capacitive loads greater than 1nF. Additionally, the LT1997-3 has more gain and phase margin as its gain is increased. Distortion The LT1997-3 features excellent distortion performance when the internal op amp is operating in the normal operating region. Operating the LT1997-3 with the internal op amp in the over the top region will increase distortion due to the lower loop gain of the op amp. Operating the LT1997-3 with input common mode voltages that go from the normal to Over-The-Top operation will significantly degrade the LT1997-3's linearity as the op amp must transition between two different input stages. Driving resistive loads significantly smaller than the 22.5k internal feedback resistor will also degrade the amplifier's linearity performance. 30 In general, the die junction temperature (TJ) can be estimated from the ambient temperature (TA), the device's power dissipation (PD) and the thermal resistance of the device and board (JA). TJ = TA + PD * JA The thermal resistance from the junction to the ambient environment (JA) is the sum of the thermal resistance from the junction to the exposed pad (JC) and the thermal resistance from the exposed pad to the ambient environment (CA). The CA value depends on how much PCB metal is connected to the exposed pad in the board. The more PCB metal that is used, the lower CA and JA will be. Power is dissipated by the amplifier's quiescent current, by the output current driving a resistive load, and by the input current driving the LT1997-3's internal resistor network. PD = (( VS+ - VS - ) *IS ) +POD +PRESD For a given supply voltage, the worst-case output power dissipation POD(MAX) occurs with the output voltage at half of either supply voltage. POD(MAX) is given by: POD(MAX) = ( VS 2)2 RLOAD The power dissipated in the internal resistors (PRESD) depends on the manner the input resistors have been configured as well as the input voltage, the output voltage and the voltage on the REF pin. The following equations and Figure 18 show the different components of PRESD corresponding to the different groups of the LT1997-3's internal resistors, assuming that the LT1997-3 is used with a dual supply configuration with +INC, -INC, and REF pins 19973f For more information www.linear.com/LT1997-3 LT1997-3 Applications Information at ground (refer to Figure 13 for resistor terminologies used in equations below). ( V+IN )2 PRESDA = RG +RF RT 2 RF RT ) ( V-IN - V+IN * RG +RF RT PRESDB = RG PD = (50 * 0.6mA ) + = 2W Assuming a thermal resistance of 45C/W, the die temperature will experience an 90C rise above ambient. This implies that the maximum ambient temperature the LT1997-3 should operate under the above conditions is: 2 (RF RT ) - V V+IN * OUT RG +RF RT PRESDD = RF TA = 150C - 90C = 60C PRESD = PRESDA + PRESDB + PRESDC + PRESDD In general, PRESD increases with higher input voltage and lower output and REF pin voltages. VS+ = 25V V+ -INA -INB -INC PRESDC PRESDD 2.5k 22.5k LT1997-3 7.5k 22.5k PRESDB - PRESDA OUT + 22.5k 7.5k 2.5k V+IN = 160V +INA +INB +INC 22.5k SHDN 12.52 1602 + 2.5k 24.75k 2 2 2 160 160 160 - 12.5 147.5 - 11 11 11 + + + 22.5k 2.5k 22.5k 2 RF RT ) ( V+IN * RG +RF RT PRESDC = RT V-IN = 160V - VOUT = 147.5V Example: For an LT1997-3 in a DFN package mounted on a PC board with a thermal resistance of 45C/W, operating on 25V supplies and driving a 2.5k load to 12.5V with V+IN = 160V and +INC = -INC = REF = 0V, the total power dissipation is given by: REF V- 19973 F18 VS- = -25V Figure 18. Power Dissipation Example VOUT = 12.5V It is recommended that the exposed pad of the DFN package have as much PCB metal connected to it as reasonably available. The more PCB metal connected to the exposed pad, the lower the thermal resistance. Connecting a large amount of PCB metal to the exposed pad can reduce the JA to even less than 45C/W. Use multiple vias from the exposed pad to the V- plane. The exposed pad is electrically connected to the V- pin. In addition, a heat sink may be necessary if operating near maximum junction temperature. The MSOP package has no exposed pad and a higher thermal resistance (JA = 130C/W). It should not be used in applications which have a high ambient temperature, require driving a heavy load, or require an extreme input voltage. Thermal Shutdown For safety, the LT1997-3 will enter shutdown mode when the die temperature rises to approximately 163C. This thermal shutdown has approximately 9C of hysteresis requiring the die temperature to cool 9C before enabling the amplifier again. 19973f For more information www.linear.com/LT1997-3 31 LT1997-3 ESD Protection The LT1997-3 is protected by a number of ESD structures. The structures are shown in Figure 19. The ESD structures serve to protect the internal circuitry but also limit signal swing on certain nodes. The structures on the +INB, -INB, +INC, -INC pins and on the internal op amp inputs limit the voltage on these nodes to 0.3V below V- and 80V above V-. The voltage on the REF (DFN), REF1 (MSOP) and REF2 (MSOP) pins are limited to 0.3V below V- and 60V above V-. The voltage on the SHDN pin is limited to 0.3V below V- and 0.3V above V+. -INA -INB V- V- V+ -INC LT1997-3 V- 2.5k 7.5k 22.5k - 22.5k OUT V- 22.5k 7.5k V- 2.5k V- + V+ 45k V- REF1 45k REF2 10A V- 19973 TA03 +INA +INB +INC V- V- SHDN 19973 F19 Figure 19. ESD Protection Typical Applications Differential Input/Output Gain of 10 Amplifier VS+ V-IN V+ -INA -INB -INC LT1997-3 2.5k 7.5k 22.5k - 22.5k OUT 10k + 22.5k - + V+OUT VOCM LT6015 7.5k 22.5k 2.5k REF 10k V-OUT +INA +INB +INC V+IN 32 SHDN V- VS- 19973 TA02 USE VOCM TO SET THE DESIRED OUTPUT COMMON MODE LEVEL 19973f For more information www.linear.com/LT1997-3 LT1997-3 Typical Applications Bidirectional Current Sense Amplifier VS+ VSOURCE = -0.3V TO 50V V+ -INA -INB -INC LT1997-3 2.5k 7.5k ILOAD 22.5k 22.5k - 22.5k + OUT RSENSE RC 7.5k 2.5k 45k REF2 45k REF1 LOAD +INA +INB +INC SHDN VOUT = VREF + 26 * ILOAD * RSENSE VREF V- 19973 TA03 Precision RRIO Single-Supply Difference Amplifier VBATTERY V+ -INA -INB -INC LT1997-3 2.5k 7.5k V-IN VCM V+IN 22.5k 22.5k - 22.5k + OUT 7.5k VCM = -0.3V TO VBATTERY 2.5k +INA +INB +INC SHDN 45k REF2 45k REF1 VOUT = VBATTERY + 9 * ( V+IN - V-IN ) 2 V- 19973 TA04 19973f For more information www.linear.com/LT1997-3 33 LT1997-3 Package Description Please refer to http://www.linear.com/product/LT1997-3#packaging for the most recent package drawings. DF Package 14(12)-Lead Plastic DFN (4mm x 4mm) (Reference LTC DWG # 05-08-1963 Rev O) 1.00 BSC 3.00 REF 0.70 0.05 4.50 0.05 3.10 0.05 1.70 0.05 3.38 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3.00 REF 4.00 0.10 (4 SIDES) 8 1.00 BSC 14 0.40 0.10 3.38 0.10 1.70 0.10 PIN 1 NOTCH 0.35 x 45 CHAMFER PIN 1 TOP MARK (NOTE 6) (DF14)(12) DFN 1113 REV 0 0.200 REF 7 R = 0.115 TYP 0.75 0.05 1 0.25 0.05 0.50 BSC BOTTOM VIEW--EXPOSED PAD 0.00 - 0.05 NOTE: 1. PACKAGE OUTLINE DOES NOT CONFORM TO JEDEC MO-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 34 19973f For more information www.linear.com/LT1997-3 LT1997-3 Package Description Please refer to http://www.linear.com/product/LT1997-3#packaging for the most recent package drawings. MS Package 16 (12)-Lead Plastic MSOP with 4 Pins Removed (Reference LTC DWG # 05-08-1847 Rev B) 1.0 (.0394) BSC 5.10 (.201) MIN 0.889 0.127 (.035 .005) 3.20 - 3.45 (.126 - .136) 4.039 0.102 (.159 .004) (NOTE 3) 16 14 121110 9 0.50 (.0197) BSC 0.305 0.038 (.0120 .0015) TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 0.280 0.076 (.011 .003) REF 3.00 0.102 (.118 .004) (NOTE 4) 4.90 0.152 (.193 .006) DETAIL "A" 0 - 6 TYP 1 GAUGE PLANE 0.53 0.152 (.021 .006) DETAIL "A" 0.18 (.007) SEATING PLANE 1.10 (.043) MAX 0.17 - 0.27 (.007 - .011) TYP 0.50 (.0197) BSC 3 567 8 1.0 (.0394) BSC 0.86 (.034) REF 0.1016 0.0508 (.004 .002) MSOP (MS12) 0213 REV B NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 19973f Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of itsinformation circuits as described herein will not infringe on existing patent rights. For more www.linear.com/LT1997-3 35 LT1997-3 Typical Application Low Noise, High CMRR Instrumentation Amplifier +15V +15V + 2.5k LT6018 + +15V 1.91k 50 - 22.5k 49.9 V+IN 22.5k 1.91k -15V - 60 7.5k - 70 LT1997-3 OUT + 22.5k 7.5k 22.5k REF 2.5k LT6018 VOUT GAIN (dB) V-IN Gain vs Frequency V+ -INA -INB -INC 40 30 20 VREF 10 0 +INA +INB +INC -15V V- SHDN -15V INPUT REFERRED NOISE = 2.1nV/Hz CMRR = 140dB 1 10 100 FREQUENCY (kHz) 1000 19973 TA05b 19973 TA05a Related Parts PART NUMBER DESCRIPTION COMMENTS LT6375 270V Common Mode Voltage Difference Amplifier 3.3V to 50V Operation, CMRR > 97dB, Input Voltage = 270V LT1990 250V Input Range Difference Amplifier 2.7V to 36V Operation, CMRR > 70dB, Input Voltage = 250V LT1991 Precision, 100A Gain Selectable Amplifier 2.7V to 36V Operation, 50V Offset, CMRR > 75dB, Input Voltage = 60V LT1996 Precision, 100A Gain Selectable Amplifier Micropower, Pin Selectable Up to Gain = 118 LT1999 High Voltage, Bidirectional Current Sense Amplifier -5V to 80V, 750V, CMRR 80dB at 100kHz, Gain: 10V/V, 20V/V, 50V/V LT6015/LT6016/ LT6017 Single, Dual, and Quad Over-The-Top Precision Op Amp 3.2MHz, 0.8V/s, 50V VOS, 3V to 50V VS, 0.335mA IS, RRIO LT6018 33V, Ultralow Noise, Precision Op Amp VOS: 50V, GBW: 15MHz, SR: 30V/s, en: 1.2nV/Hz, IS: 7.2mA LTC6090 140V Operational Amplifier 50pA IB, 1.6mV VOS, 9.5V to 140V VS, 4.5mA IS, RR Output LT6108 High Side Current Sense Amplifier with Reference and Comparator with Shutdown 2.7V to 60V, 125V, Resistor Set Gain, 1.25% Threshold Error LT1787/LT1787HV Precision, Bidirectional High Side Current Sense Amplifier 2.7V to 60V Operation, 75V Offset, 60A Current Draw LT6100 Gain-Selectable High Side Current Sense Amplifier 4.1V to 48V Operation, Pin-Selectable Gain: 10V/V, 12.5V/V, 20V/V, 25V/V, 40V/V, 50V/V LTC6101/ LTC6101HV High Voltage High Side Current Sense Amplifier 4V to 60V/5V to 100V Operation, External Resistor Set Gain, SOT23 LTC6102/ LTC6102HV Zero Drift High Side Current Sense Amplifier 4V to 60V/5V to 100V Operation, 10V Offset, 1s Step Response, MSOP8/DFN Packages LTC6104 Bidirectional, High Side Current Sense 4V to 60V, Gain Configurable, 8-Pin MSOP Package 36 19973f LT 0317 * PRINTED IN USA For more information www.linear.com/LT1997-3 www.linear.com/LT1997-3 LINEAR TECHNOLOGY CORPORATION 2017