LTC1992 Family Low Power, Fully Differential Input/Output Amplifier/Driver Family FEATURES DESCRIPTION n The LTC(R)1992 product family consists of five fully differential, low power amplifiers. The LTC1992 is an unconstrained fully differential amplifier. The LTC1992-1, LTC1992-2, LTC1992-5 and LTC1992-10 are fixed gain blocks (with gains of 1, 2, 5 and 10 respectively) featuring precision on-chip resistors for accurate and ultrastable gain. All of the LTC1992 parts have a separate internal common mode feedback path for outstanding output phase balancing and reduced second order harmonics. The VOCM pin sets the output common mode level independent of the input common mode level. This feature makes level shifting of signals easy. n n n n n n n n n n n n Available with Adjustable Gain or Fixed Gain of 1, 2, 5 or 10 0.3% (Max) Gain Error from -40C to 85C 3.5ppm/C Gain Temperature Coefficient 5ppm Gain Long Term Stability Fully Differential Input and Output CLOAD Stable up to 10,000pF Adjustable Output Common Mode Voltage Rail-to-Rail Output Swing Low Supply Current: 1mA (Max) High Output Current: 10mA (Min) Specified on a Single 2.7V to 5V Supply DC Offset Voltage <2.5mV (Max) Available in 8-Lead MSOP Package The amplifiers' differential inputs operate with signals ranging from rail-to-rail with a common mode level from the negative supply up to 1.3V from the positive supply. The differential input DC offset is typically 250V. The rail-to-rail outputs sink and source 10mA. The LTC1992 is stable for all capacitive loads up to 10,000pF. APPLICATIONS n n n n n Differential Driver/Receiver Differential Amplification Single-Ended to Differential Conversion Level Shifting Trimmed Phase Response for Multichannel Systems The LTC1992 can be used in single supply applications with supply voltages as low as 2.7V. It can also be used with dual supplies up to 5V. The LTC1992 is available in an 8-pin MSOP package. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Single-Supply, Single-Ended to Differential Conversion 10k 5V 5V 3 10k VIN 0V -5V 1 7 2 10k 0.01F INPUT SIGNAL FROM A 5V SYSTEM 8 - + VMID VOCM 4 VIN (5V/DIV) 5V 2.5V 0V +OUT LTC1992 + - 5 6 OUTPUT SIGNAL FROM A SINGLE-SUPPLY SYSTEM 10k 1992 TA01a 5V 5V 2.5V 0V 0V -5V 5V (2V/DIV) -OUT 0V 1992 TA01b 1992fb 1 LTC1992 Family ABSOLUTE MAXIMUM RATINGS (Note 1) Total Supply Voltage (+VS to -VS) .............................12V Maximum Voltage on any Pin ................ (-VS - 0.3V) VPIN (+VS + 0.3V) Output Short-Circuit Duration (Note 3) ............ Indefinite Operating Temperature Range (Note 5) LTC1992CMS8/LTC1992-XCMS8/ LTC1992IMS8/LTC1992-XIMS8 ...........-40C to 85C LTC1992HMS8/LTC1992-XHMS8 ...... -40C to 125C Specified Temperature Range (Note 6) LTC1992CMS8/LTC1992-XCMS8 ............. 0C to 70C LTC1992IMS8/LTC1992-XIMS8 ...........-40C to 85C LTC1992HMS8/LTC1992-XHMS8 ...... -40C to 125C Storage Temperature Range ................. -65C to 150C Lead Temperature (Soldering, 10 sec)................... 300C PIN CONFIGURATION LTC1992 LTC1992-X TOP VIEW -IN 1 VOCM 2 +VS 3 +OUT 4 + - +- 8 7 6 5 TOP VIEW -IN 1 VOCM 2 +VS 3 +OUT 4 +IN VMID -VS -OUT MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 250C/W + - +- 8 7 6 5 +IN VMID -VS -OUT MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 250C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE LTC1992CMS8#PBF LTC1992CMS8#TRPBF LTYU 8-Lead Plastic MSOP 0C to 70C LTC1992IMS8#PBF LTC1992IMS8#TRPBF LTYU 8-Lead Plastic MSOP -40C to 85C LTC1992HMS8#PBF LTC1992HMS8#TRPBF LTYU 8-Lead Plastic MSOP -40C to 125C LTC1992-1CMS8#PBF LTC1992-1CMS8#TRPBF LTACJ 8-Lead Plastic MSOP 0C to 70C LTC1992-1IMS8#PBF LTC1992-1IMS8#TRPBF LTACJ 8-Lead Plastic MSOP -40C to 85C LTC1992-1HMS8#PBF LTC1992-1HMS8#TRPBF LTACJ 8-Lead Plastic MSOP -40C to 125C LTC1992-2CMS8#PBF LTC1992-2CMS8#TRPBF LTYV 8-Lead Plastic MSOP 0C to 70C LTC1992-2IMS8#PBF LTC1992-2IMS8#TRPBF LTYV 8-Lead Plastic MSOP -40C to 85C LTC1992-2HMS8#PBF LTC1992-2HMS8#TRPBF LTYV 8-Lead Plastic MSOP -40C to 125C LTC1992-5CMS8#PBF LTC1992-5CMS8#TRPBF LTACK 8-Lead Plastic MSOP 0C to 70C LTC1992-5IMS8#PBF LTC1992-5IMS8#TRPBF LTACK 8-Lead Plastic MSOP -40C to 85C LTC1992-5HMS8#PBF LTC1992-5HMS8#TRPBF LTACK 8-Lead Plastic MSOP -40C to 125C LTC1992-10CMS8#PBF LTC1992-10CMS8#TRPBF LTACL 8-Lead Plastic MSOP 0C to 70C LTC1992-10IMS8#PBF LTC1992-10IMS8#TRPBF LTACL 8-Lead Plastic MSOP -40C to 85C LTC1992-10HMS8#PBF LTC1992-10HMS8#TRPBF LTACL 8-Lead Plastic MSOP -40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. 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/ 1992fb 2 LTC1992 Family ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. +VS = 5V, -VS = 0V, VINCM = VOUTCM = VOCM = 2.5V, unless otherwise noted. VOCM is the voltage on the VOCM pin. VOUTCM is defined as (+VOUT + -VOUT)/2. VINCM is defined as (+VIN + -VIN)/2. VINDIFF is defined as (+VIN - -VIN). VOUTDIFF is defined as (+VOUT - -VOUT). Specifications applicable to all parts in the LTC1992 family. ALL C AND I GRADE SYMBOL PARAMETER CONDITIONS VS Supply Voltage Range l Supply Current l TYP 2.7 ALL H GRADE MAX MIN 11 2.7 TYP MAX UNITS 11 V l 0.65 0.75 0.7 0.8 1.0 1.2 1.2 1.5 0.65 0.8 0.7 0.9 1.0 1.5 1.2 1.8 mA mA mA mA VS = 2.7V VS = 5V VS = 5V l l l 0.25 0.25 0.25 2.5 2.5 2.5 0.25 0.25 0.25 4 4 4 mV mV mV VOSDIFF/T Differential Offset Voltage Drift (Input Referred) (Note 7) VS = 2.7V VS = 5V VS = 5V l l l 10 10 10 PSRR Power Supply Rejection Ratio (Input Referred) (Note 7) VS = 2.7V to 5V l GCM Common Mode Gain(VOUTCM/VOCM) Common Mode Gain Error Output Balance (VOUTCM/(VOUTDIFF) VOUTDIFF = -2V to +2V l l l 1 0.1 -85 0.3 -60 1 0.1 -85 0.35 -60 % dB Common Mode Offset Voltage (VOUTCM - VOCM) VS = 2.7V VS = 5V VS = 5V l l l 0.5 1 2 12 15 18 0.5 1 2 15 17 20 mV mV mV VS = 2.7V VS = 5V VS = 5V l l l 10 10 10 IS VS = 2.7V to 5V MIN VS = 5V VOSDIFF VOSCM Differential Offset Voltage (Input Referred) (Note 7) VOSCM/T Common Mode Offset Voltage Drift 75 VOUTCMR Output Signal Common Mode Range (Voltage Range for the VOCM Pin) l (-VS) + 0.5V RINVOCM Input Resistance, VOCM Pin l l IBVOCM Input Bias Current, VOCM Pin VMID Voltage at the VMID Pin VOUT VS = 2.7V to 5V 80 72 80 dB (+VS) - 1.3V (-VS) + 0.5V 2.44 2.50 Output Voltage, High (Note 2) l VS = 2.7V, Load = 10k VS = 2.7V, Load = 5mA l VS = 2.7V, Load = 10mA l 2.60 2.50 2.29 2.69 2.61 2.52 Output Voltage, Low (Note 2) l VS = 2.7V, Load = 10k VS = 2.7V, Load = 5mA l VS = 2.7V, Load = 10mA l Output Voltage, High (Note 2) VS = 5V, Load = 10k VS = 5V, Load = 5mA VS = 5V, Load = 10mA l l l Output Voltage, Low (Note 2) VS = 5V, Load = 10k VS = 5V, Load = 5mA VS = 5V, Load = 10mA l l l Output Voltage, High (Note 2) l VS = 5V, Load = 10k VS = 5V, Load = 5mA l VS = 5V, Load = 10mA l Output Voltage, Low (Note 2) l VS = 5V, Load = 10k VS = 5V, Load = 5mA l VS = 5V, Load = 10mA l 0.02 0.10 0.20 2.43 2.50 2.60 2.50 2.29 2.69 2.61 2.52 0.10 0.25 0.35 0.02 0.10 0.20 4.90 4.80 4.70 0.10 0.25 0.35 4.99 4.89 4.80 -4.99 -4.90 -4.80 (+VS) - 1.3V 4.85 4.80 4.60 -4.90 -4.75 -4.65 pA 2.57 0.10 0.25 0.41 V V V V V V 0.10 0.30 0.42 4.99 4.89 4.80 -4.98 -4.90 -4.80 V V V V 4.99 4.90 4.81 0.02 0.10 0.20 V M 2 2.56 4.99 4.90 4.81 0.02 0.10 0.20 V/C V/C V/C 500 2 l 4.90 4.85 4.65 V/C V/C V/C 10 10 10 500 4.90 4.85 4.75 10 10 10 V V V V V V -4.85 -4.75 -4.55 V V V 1992fb 3 LTC1992 Family ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. +VS = 5V, -VS = 0V, VINCM = VOUTCM = VOCM = 2.5V, unless otherwise noted. VOCM is the voltage on the VOCM pin. VOUTCM is defined as (+VOUT + -VOUT)/2. VINCM is defined as (+VIN + -VIN)/2. VINDIFF is defined as (+VIN - -VIN). VOUTDIFF is defined as (+VOUT - -VOUT). Specifications applicable to all parts in the LTC1992 family. ALL C AND I GRADE SYMBOL PARAMETER CONDITIONS ISC Output Short-Circuit Current Sourcing (Notes 2,3) Output Short-Circuit Current Sinking (Notes 2,3) AVOL MIN TYP VS = 2.7V, VOUT =1.35V l l VS = 5V, VOUT = 2.5V l VS = 5V, VOUT = 0V 20 20 20 VS = 2.7V, VOUT =1.35V l l VS = 5V, VOUT = 2.5V l VS = 5V, VOUT = 0V 13 13 13 l Large-Signal Voltage Gain MAX ALL H GRADE MIN TYP 30 30 30 20 20 20 30 30 30 mA mA mA 30 30 30 13 13 13 30 30 30 mA mA mA 80 dB 80 MAX UNITS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. +VS = 5V, -VS = 0V, VINCM = VOUTCM = VOCM = 2.5V, unless otherwise noted. VOCM is the voltage on the VOCM pin. VOUTCM is defined as (+VOUT + -VOUT)/2. VINCM is defined as (+VIN + -VIN)/2. VINDIFF is defined as (+VIN - -VIN). VOUTDIFF is defined as (+VOUT - -VOUT). Specifications applicable to the LTC1992 only. LTC1992CMS8 LTC1992ISM8 SYMBOL PARAMETER CONDITIONS MIN LTC1992HMS8 TYP MAX TYP MAX UNITS IB Input Bias Current VS = 2.7V to 5V l 2 250 MIN 2 400 pA IOS Input Offset Current VS = 2.7V to 5V l 0.1 100 0.1 150 pA RIN Input Resistance l 500 500 M CIN Input Capacitance l 3 3 pF en Input Referred Noise Voltage Density f = 1kHz 35 35 nV/Hz in Input Noise Current Density VINCMR Input Signal Common Mode Range CMRR Common Mode Rejection Ratio (Input Referred) SR Slew Rate (Note 4) GBW Gain-Bandwidth Product (fTEST = 100kHz) f = 1kHz 1 l (-VS) - 0.1V VINCM = -0.1V to 3.7V l 69 90 l 0.5 1.5 l l 3.0 2.5 1.9 3.2 3.0 TA = 25C LTC1992CMS8 LTC1992IMS8/ LTC1992HMS8 1 (+VS) - 1.3V (-VS) - 0.1V 69 3.5 4.0 4.0 90 0.5 1.5 3.0 3.2 1.9 fA/Hz (+VS) - 1.3V V dB V/s 3.5 4.0 MHz MHz MHz 1992fb 4 LTC1992 Family ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. +VS = 5V, -VS = 0V, VINCM = VOUTCM = VOCM = 2.5V, unless otherwise noted. VOCM is the voltage on the VOCM pin. VOUTCM is defined as (+VOUT + -VOUT)/2. VINCM is defined as (+VIN + -VIN)/2. VINDIFF is defined as (+VIN - -VIN). VOUTDIFF is defined as (+VOUT - -VOUT). Typical values are at TA = 25C. Specifications apply to the LTC1992-1 only. LTC1992-1CMS8 LTC1992-1ISM8 SYMBOL PARAMETER GDIFF CONDITIONS Differential Gain Differential Gain Error Differential Gain Nonlinearity Differential Gain Temperature Coefficient MIN 1 0.1 50 3.5 l l en Input Referred Noise Voltage Density (Note 7) f = 1kHz RIN Input Resistance, Single-Ended +IN, -IN Pins TYP MAX LTC1992-1HMS8 MIN 1 0.1 50 3.5 0.3 45 l 22.5 30 TYP MAX 0.35 45 37.5 22 V/V % ppm ppm/C nV/Hz 30 -0.1V to 4.9V UNITS 38 k VINCMR Input Signal Common Mode Range VS = 5V -0.1V to 4.9V V CMRR Common Mode Rejection Ratio (Amplifier Input Referred) (Note 7) VINCM = -0.1V to 3.7V l 55 60 55 60 dB SR Slew Rate (Note 4) l 0.5 1.5 0.5 1.5 V/s GBW Gain-Bandwidth Product 3 MHz fTEST = 180kHz 3 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. +VS = 5V, -VS = 0V, VINCM = VOUTCM = VOCM = 2.5V, unless otherwise noted. VOCM is the voltage on the VOCM pin. VOUTCM is defined as (+VOUT + -VOUT)/2. VINCM is defined as (+VIN + -VIN)/2. VINDIFF is defined as (+VIN - -VIN). VOUTDIFF is defined as (+VOUT - -VOUT). Typical values are at TA = 25C. Specifications apply to the LTC1992-2 only. LTC1992-2CMS8 LTC1992-2ISM8 SYMBOL PARAMETER GDIFF CONDITIONS Differential Gain Differential Gain Error Differential Gain Nonlinearity Differential Gain Temperature Coefficient MIN 2 0.1 50 3.5 l l en Input Referred Noise Voltage Density (Note 7) f = 1kHz RIN Input Resistance, Single-Ended +IN, -IN Pins TYP MAX LTC1992-2HMS8 MIN 2 0.1 50 3.5 0.3 45 l 22.5 30 TYP MAX 0.35 45 37.5 22 V/V % ppm ppm/C nV/Hz 38 k VINCMR Input Signal Common Mode Range VS = 5V -0.1V to 4.9V V CMRR Common Mode Rejection Ratio (Amplifier Input Referred) (Note 7) VINCM = -0.1V to 3.7V l 55 60 55 60 dB SR Slew Rate (Note 4) l 0.7 2 0.7 2 V/s GBW Gain-Bandwidth Product 4 MHz fTEST = 180kHz -0.1V to 4.9V 30 UNITS 4 1992fb 5 LTC1992 Family ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. +VS = 5V, -VS = 0V, VINCM = VOUTCM = VOCM = 2.5V, unless otherwise noted. VOCM is the voltage on the VOCM pin. VOUTCM is defined as (+VOUT + -VOUT)/2. VINCM is defined as (+VIN + -VIN)/2. VINDIFF is defined as (+VIN - -VIN). VOUTDIFF is defined as (+VOUT - -VOUT). Typical values are at TA = 25C. Specifications apply to the LTC1992-5 only. LTC1992-5CMS8 LTC1992-5ISM8 SYMBOL PARAMETER GDIFF CONDITIONS Differential Gain Differential Gain Error Differential Gain Nonlinearity Differential Gain Temperature Coefficient MIN 5 0.1 50 3.5 l l en Input Referred Noise Voltage Density (Note 7) f = 1kHz RIN Input Resistance, Single-Ended +IN, -IN Pins TYP MAX LTC1992-5HMS8 MIN 5 0.1 50 3.5 0.3 45 l 22.5 30 TYP MAX 0.35 45 37.5 22 -0.1V to 3.9V 30 UNITS V/V % ppm ppm/C nV/Hz 38 k VINCMR Input Signal Common Mode Range VS = 5V -0.1V to 3.9V V CMRR Common Mode Rejection Ratio (Amplifier Input Referred) (Note 7) VINCM = -0.1V to 3.7V l 55 60 55 60 dB SR Slew Rate (Note 4) l 0.7 2 0.7 2 V/s GBW Gain-Bandwidth Product 4 MHz fTEST = 180kHz 4 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. +VS = 5V, -VS = 0V, VINCM = VOUTCM = VOCM = 2.5V, unless otherwise noted. VOCM is the voltage on the VOCM pin. VOUTCM is defined as (+VOUT + -VOUT)/2. VINCM is defined as (+VIN + -VIN)/2. VINDIFF is defined as (+VIN - -VIN). VOUTDIFF is defined as (+VOUT - -VOUT). Typical values are at TA = 25C. Specifications apply to the LTC1992-10 only. LTC1992-10CMS8 LTC1992-10ISM8 SYMBOL PARAMETER GDIFF CONDITIONS Differential Gain Differential Gain Error Differential Gain Nonlinearity Differential Gain Temperature Coefficient MIN 10 0.1 50 3.5 l l en Input Referred Noise Voltage Density (Note 7) f = 1kHz RIN Input Resistance, Single-Ended +IN, -IN Pins TYP MAX LTC1992-10HMS8 MIN 10 0.1 50 3.5 0.3 45 l 11.3 15 TYP MAX 0.35 45 18.8 11 V/V % ppm ppm/C nV/Hz 19 k VINCMR Input Signal Common Mode Range VS = 5V -0.1V to 3.8V V CMRR Common Mode Rejection Ratio (Amplifier Input Referred) (Note 7) VINCM = -0.1V to 3.7V l 55 60 55 60 dB SR Slew Rate (Note 4) l 0.7 2 0.7 2 V/s GBW Gain-Bandwidth Product 4 MHz fTEST = 180kHz 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: Output load is connected to the midpoint of the +VS and -VS potentials. Measurement is taken single-ended, one output loaded at a time. Note 3: A heat sink may be required to keep the junction temperature below the absolute maximum when the output is shorted indefinitely. Note 4: Differential output slew rate. Slew rate is measured single ended and doubled to get the listed numbers. Note 5: The LTC1992C/LTC1992-XC/LTC1992I/LTC1992-XI are guaranteed functional over an operating temperature of -40C to 85C. The -0.1V to 3.8V 15 UNITS 4 LTC1992H/LTC1992-XH are guaranteed functional over the extended operating temperature of -40C to 125C. Note 6: The LTC1992C/LTC1992-XC are guaranteed to meet the specified performance limits over the 0C to 70C temperature range and are designed, characterized and expected to meet the specified performance limits over the -40C to 85C temperature range but are not tested or QA sampled at these temperatures. The LTC1992I/LTC1992-XI are guaranteed to meet the specified performance limits over the -40C to 85C temperature range. The LTC1992H/LTC1992-XH are guaranteed to meet the specified performance limits over the -40C to 125C temperature range. Note 7: Differential offset voltage, differential offset voltage drift, CMRR, noise voltage density and PSRR are referred to the internal amplifier's input to allow for direct comparison of gain blocks with discrete amplifiers. 1992fb 6 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Differential Input Offset Voltage vs Temperature (Note 7) 0.6 1.0 DIFFERENTIAL VOS (mV) SUPPLY CURRENT (mA) 0.4 85C 25C 0.7 0.6 -40C 0.5 0.4 0.3 0 VS = 1.35V VS = 2.5V -0.2 -0.4 VS = 5V -0.6 0.1 0 1 2 3 4 5 6 7 8 TOTAL SUPPLY VOLTAGE (V) 9 -0.8 -40 10 85 25 TEMPERATURE (C) -1 -2 -3 -5 -40 125 25 85 TEMPERATURE (C) 125 1992 G03 Common Mode Offset Voltage vs VOCM Voltage 5 85C 0 125C 0 85C -10 -5 VOCM VOS (mV) VOCM VOS (mV) 25C -40C -40C -10 -15 +V = 5V S -VS = 0V VINCM = 2.5V -20 0 0.5 1 1.5 2 2.5 3 3.5 VOCM VOLTAGE (V) -15 +V = 2.7V S -VS = 0V VINCM = 1.35V -20 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 VOCM VOLTAGE (V) 1992 G04 4 0.8 2.65 0.7 0.6 85C 25C -10 5 3 4 5 1992 G06 0.4 25C 2.45 0.3 85C -40C 125C 1.0 4.95 0.9 4.90 0.8 4.80 4.65 0.2 25C 4.75 4.70 0.7 125C -40C 85C 0.6 85C 0.5 25C 0.4 125C 4.60 0.3 -40C 0.2 2.35 0.1 4.55 0.1 2.30 0 5 -20 -15 -10 -5 10 LOAD CURRENT (mA) 0 4.50 -20 -15 -10 -5 0 5 10 LOAD CURRENT (mA) 0 15 20 1992 G07 -SWING (V) 0.5 -SWING (V) 2.55 -40C -40C 5.00 4.85 +SWING (V) 125C 2.50 -5 Output Voltage Swing vs Output Load, VS = 5V 2.70 2.60 4.5 25C -15 +V = 5V S -VS = -5V VINCM = 0V -20 -5 -4 -3 -2 -1 0 1 2 VOCM VOLTAGE (V) 1992 G05 Output Voltage Swing vs Output Load, VS = 2.7V +SWING (V) VS = 1.35V 125C 25C VOCM VOS (mV) VS = 2.5V 0 5 85C 2.40 1 Common Mode Offset Voltage vs VOCM Voltage 125C 0 VS = 5V 2 1992 G02 Common Mode Offset Voltage vs VOCM Voltage 5 VINCM = 0V VOCM = 0V -4 1992 G01 -5 3 0.2 0.2 0 4 VINCM = 0V VOCM = 0V 125C 0.8 Common Mode Offset Voltage vs Temperature COMMON MODE VOS (mV) Supply Current vs Supply Voltage 0.9 Applicable to all parts in the LTC1992 family. 15 20 1992 G08 1992fb 7 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Applicable to all parts in the LTC1992 family. VOCM Input Bias Current vs VOCM Voltage Output Voltage Swing vs Output Load, VS = 5V 5.0 Differential Input Offset Voltage vs Time (Normalized to t = 0) 10E-9 -3.8 100 TEMP = 35C -4.0 -40C -4.2 25C 4.7 -4.4 125C 85C 85C 4.6 125C -4.6 25C 4.5 -4.8 -40C 4.4 5 10 0 -20 -15 -10 -5 LOAD CURRENT (mA) -SWING (V) -5.0 15 20 100E-12 85C 10E-12 -40C 1E-12 100E-15 0 Differential Gain vs Time (Normalized to t = 0) 0.5 1 40 20 0 -20 -40 25C -60 +VS = 5V -VS = 0V VINCM = 2.5V 1992 G09 10 60 -80 -100 1.5 2 2.5 3 3.5 VOCM VOLTAGE (V) 4 4.5 0 5 400 2000 Input Common Mode Overdrive Recovery (Detailed View) TEMP = 35C BOTH INPUTS (INPUTS TIED TOGETHER) BOTH INPUTS (INPUTS TIED TOGETHER) 6 1600 1992 G11 Input Common Mode Overdrive Recovery (Expanded View) 8 800 1200 TIME (HOURS) 1992 G10 DELTA GAIN (ppm) 4 1V/DIV 2 0 1V/DIV +SWING (V) 4.8 125C 1E-9 DELTA VOS (V) 4.9 VOCM INPUT BIAS CURRENT (A) 80 OUTPUTS OUTPUTS -2 -4 +VS = 2.5V -VS = -2.5V VOCM = 0V LTC1992-10 SHOWN FOR REFERENCE -6 -8 -10 0 400 800 1200 TIME (HOURS) 1600 2000 +VS = 2.5V -VS = -2.5V VOCM = 0V LTC1992-10 SHOWN FOR REFERENCE 1992 G13 50s/DIV 1s/DIV 1992 G14 1992 G12 Output Overdrive Recovery (Expanded View) Output Overdrive Recovery (Detailed View) INPUTS 1V/DIV 1V/DIV +VS = 2.5V, -VS = -2.5V, VOCM = 0V OUTPUTS OUTPUTS +VS = 2.5V -VS = -2.5V VOCM = 0V LTC1992-2 SHOWN FOR REFERENCE LTC1992-2 SHOWN FOR REFERENCE 50s/DIV INPUTS 1992 G15 5s/DIV 1992 G16 1992fb 8 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Differential Gain vs Frequency, VS = 2.5V CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF 100 1000 FREQUENCY (kHz) 12 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -54 -60 -66 -20 CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF 10 10000 -140 -160 -180 100 1000 FREQUENCY (kHz) 10 10000 -40C 125C 85C -1.0 -1.5 2.0 1.0 0.5 -40C 0 125C -0.5 -2.0 25C 85C -1.0 0.5 -40C 0 125C -1.0 100 VS VAMPDIFF 90 -VS 70 PSRR (dB) +VS 60 50 40 30 -40 -60 -80 20 20 VOUTCM VOUTDIFF -20 80 80 5 Output Balance vs Frequency 0 OUTPUT BALANCE (dB) VAMPCM VAMPDIFF 4 1922 G22 Power Supply Rejection Ratio vs Frequency (Note 7) 40 85C 1922 G21 Common Mode Rejection Ratio vs Frequency (Note 7) 60 25C -0.5 -2.0 -5 -4 -3 -2 -1 0 1 2 3 COMMON MODE VOLTAGE (V) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 COMMON MODE VOLTAGE (V) 1922 G20 100 1.0 -1.5 -2.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 COMMON MODE VOLTAGE (V) +VS = 5V -VS = -5V VOCM = 0V 1.5 -1.5 120 1000 Differential Input Offset Voltage vs Input Common Mode Voltage DIFFERENTIAL VOS (mV) 0.5 100 FREQUENCY (kHz) 1992 G37 +VS = 5V 1.5 -VS = 0V VOCM = 2.5V 1.0 0 CLOAD = 10pF 50pF 100pF 500pF 1000pF 5000pF 10000pF -120 2.0 DIFFERENTIAL VOS (mV) DIFFERENTIAL VOS (mV) -80 -100 Differential Input Offset Voltage vs Input Common Mode Voltage +VS = 2.7V -VS = 0V 1.5 VOCM = 1.35V CMRR (dB) -60 1992 G18 2.0 25C RIN = RFB = 10k -40 Differential Input Offset Voltage vs Input Common Mode Voltage -0.5 0 RIN = RFB = 10k 1992 G17 0 Differential Phase Response vs Frequency PHASE (DEG) RIN = RFB = 10k GAIN (dB) GAIN (dB) Differential Input Differential Gain vs Frequency, VS = 2.5V 12 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -54 -60 -66 10 Applicable to the LTC1992 only. 10 0 100 1k 10k 100k FREQUENCY (Hz) 1M 1992 G23 -100 0 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G24 1 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G25 1992fb 9 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS 0V VOUTDIFF (1V/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 1.5V -VIN = 1.5V CLOAD = 0pF GAIN = 1 Differential Input Large-Signal Step Response +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 1.5V -VIN = 1.5V GAIN = 1 VOUTDIFF (1V/DIV) Differential Input Large-Signal Step Response Applicable to the LTC1992 only. 0V CLOAD = 10000pF CLOAD = 1000pF 2s/DIV 20s/DIV 1992 G26 +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 4V -VIN = 2V CLOAD = 0pF GAIN = 1 2.5V Single-Ended Input Large-Signal Step Response VOUTDIFF (1V/DIV) VOUTDIFF (1V/DIV) Single-Ended Input Large-Signal Step Response 1992 G27 +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 4V -VIN = 2V GAIN = 1 2.5V CLOAD = 10000pF CLOAD = 1000pF 2s/DIV 20s/DIV 1992 G28 0V VOUTDIFF (50mV/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 50mV -VIN = 50mV CLOAD = 0pF GAIN = 1 Differential Input Small-Signal Step Response +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 50mV -VIN = 50mV GAIN = 1 VOUTDIFF (50mV/DIV) Differential Input Small-Signal Step Response 1992 G29 0V CLOAD = 10000pF CLOAD = 1000pF 1s/DIV 1992 G30 10s/DIV 1992 G31 1992fb 10 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Applicable to the LTC1992 only. Single-Ended Input Small-Signal Step Response Single-Ended Input Small-Signal Step Response VOUTDIFF (50mV/DIV) VOUTDIFF (50mV/DIV) CLOAD = 10000pF CLOAD = 1000pF 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 200mV -VIN = 100mV CLOAD = 0pF GAIN = 1 1s/DIV 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 200mV -VIN = 100mV GAIN = 1 10s/DIV 1992 G32 THD + Noise vs Frequency THD + Noise vs Amplitude -40 -40 500kHz MEASUREMENT BANDWIDTH +VS = 5V -50 -VS = -5V VOCM = 0V THD + NOISE (dB) THD + NOISE (dB) 500kHz MEASUREMENT BANDWIDTH +VS = 5V -50 -VS = -5V VOCM = 0V -60 VOUT = 10VP-PDIFF VOUT = 5VP-PDIFF -70 1992 G33 VOUT = 1VP-PDIFF -80 -60 50kHz 20kHz -70 10kHz -80 5kHz VOUT = 2VP-PDIFF -90 -90 2kHz -100 100 1k 10k FREQUENCY (Hz) 50k 0.1 1 10 INPUT SIGNAL AMPLITUDE (VP-PDIFF) 1992 G34 20 1992 G35 Differential Noise Voltage Density vs Frequency VOCM Gain vs Frequency, VS = 2.5V 1000 5 CLOAD = 10pF TO 10000pF 0 -5 GAIN (dB) INPUT REFERRED NOISE (nVHz) 1kHz -100 100 -10 -15 -20 -25 -30 -35 10 10 100 1000 FREQUENCY (Hz) 10000 1922 G36 10 100 1000 FREQUENCY (kHz) 10000 1992 G19 1992fb 11 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Differential Gain vs Frequency, VS = 2.5V CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF 100 1000 FREQUENCY (kHz) 10000 0 12 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -54 -60 -66 10 -20 -40 -60 -80 CLOAD = 10pF 50pF 100pF 500pF 1000pF 5000pF 10000pF -100 CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF -120 -140 -160 -180 100 1000 FREQUENCY (kHz) 10 10000 100 FREQUENCY (kHz) 1000 1992 G40 1992 G39 1992 G38 Differential Gain Error vs Temperature VOCM Gain vs Frequency 0.025 5 0.020 0 0.015 CLOAD = 10pF TO 10000pF -5 0.010 0.005 GAIN (dB) GAIN ERROR (%) Differential Phase Response vs Frequency PHASE (DEG) GAIN (dB) GAIN (dB) Differential Input Differential Gain vs Frequency, VS = 2.5V 12 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -54 -60 -66 10 Applicable to the LTC1992-1 only. 0 -0.005 -0.010 -10 -15 -20 -25 -0.015 -30 -0.020 -0.025 -50 -35 -25 50 25 0 75 TEMPERATURE (C) 100 10 125 100 1000 FREQUENCY (kHz) 1992 G41 Differential Input Offset Voltage vs Input Common Mode Voltage 1 -40C 125C -1 -2 85C 5 +VS = 5V 4 -VS = 0V VOCM = 2.5V 3 4 2 1 0 -40C 125C -1 -2 25C 85C DIFFERENTIAL VOS (mV) DIFFERENTIAL VOS (mV) DIFFERENTIAL VOS (mV) 2 25C Differential Input Offset Voltage vs Input Common Mode Voltage 5 +VS = 2.7V 4 -VS = 0V VOCM = 1.35V 3 0 1992 G42 Differential Input Offset Voltage vs Input Common Mode Voltage 5 3 1 -3 -4 1922 G43 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 COMMON MODE VOLTAGE (V) 1922 G44 85C 25C -2 -4 -5 -40C -1 -4 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 COMMON MODE VOLTAGE (V) 125C 0 -3 0 +VS = 5V -VS = -5V VOCM = 0V 2 -3 -5 10000 -5 -5 -4 -3 -2 -1 0 1 2 3 COMMON MODE VOLTAGE (V) 4 5 1922 G45 1992fb 12 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Common Mode Rejection Ratio vs Frequency 100 +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 1.5V -VIN = 1.5V 90 80 70 CMRR (dB) 0V VOUTDIFF (1V/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 1.5V -VIN = 1.5V CLOAD = 0pF Differential Input Large-Signal Step Response VOUTDIFF (1V/DIV) Differential Input Large-Signal Step Response Applicable to the LTC1992-1 only. 0V 60 50 40 30 20 CLOAD = 10000pF CLOAD = 1000pF 2s/DIV 20s/DIV 1992 G46 VAMPCM VAMPDIFF 10 0 100 1992 G47 1k 10k 100k FREQUENCY (Hz) 1M 1992 G48 2.5V Power Supply Rejection Ratio vs Frequency 100 +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 4V -VIN = 2V 90 80 70 PSRR (dB) +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 4V -VIN = 2V CLOAD = 0pF Single-Ended Input Large-Signal Step Response VOUTDIFF (1V/DIV) VOUTDIFF (1V/DIV) Single-Ended Input Large-Signal Step Response 2.5V -VS 60 +VS 50 40 30 20 CLOAD = 10000pF CLOAD = 1000pF 2s/DIV 20s/DIV 1992 G49 VS VAMPDIFF 10 0 1992 G50 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G51 +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 50mV -VIN = 50mV 0V Output Balance vs Frequency 0 -20 OUTPUT BALANCE (dB) 0V VOUTDIFF (50mV/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 50mV -VIN = 50mV CLOAD = 0pF Differential Input Small-Signal Step Response VOUTDIFF (50mV/DIV) Differential Input Small-Signal Step Response -40 -60 -80 CLOAD = 10000pF CLOAD = 1000pF 1s/DIV 1992 G52 10s/DIV 1992 G53 VOUTCM VOUTDIFF -100 1 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G54 1992fb 13 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Small-Signal Step Response Applicable to the LTC1992-1 only. Single-Ended Input Small-Signal Step Response Differential Noise Voltage Density vs Frequency 1000 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 200mV -VIN = 100mV CLOAD = 0pF 1s/DIV INPUT REFERRED NOISE (nVHz) VOUTDIFF (50mV/DIV) VOUTDIFF (50mV/DIV) CLOAD = 10000pF CLOAD = 1000pF 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 200mV -VIN = 100mV 10 10s/DIV 1992 G55 100 1992 G56 100 1000 FREQUENCY (Hz) 10 10000 1922 G57 THD + Noise vs Frequency THD + Noise vs Amplitude -40 -40 -60 500kHz MEASUREMENT BANDWIDTH +VS = 5V -50 -VS = -5V VOCM = 0V THD + NOISE (dB) THD + NOISE (dB) 500kHz MEASUREMENT BANDWIDTH +VS = 5V -50 -VS = -5V VOCM = 0V VOUT = 10VP-PDIFF VOUT = 5VP-PDIFF -70 VOUT = 1VP-PDIFF -80 -60 50kHz 20kHz -70 10kHz -80 5kHz VOUT = 2VP-PDIFF -90 -90 2kHz -100 100 1kHz -100 1k 10k FREQUENCY (Hz) 50k 1992 G58 0.1 1 10 INPUT SIGNAL AMPLITUDE (VP-PDIFF) 20 1992 G59 1992fb 14 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Differential Gain vs Frequency, VS = 2.5V CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF 10 100 1000 FREQUENCY (kHz) 10000 Differential Phase Response vs Frequency 0 18 12 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -54 -60 -66 10 -20 -40 PHASE (DEG) GAIN (dB) GAIN (dB) Differential Input Differential Gain vs Frequency, VS = 2.5V 18 12 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -54 -60 -66 Applicable to the LTC1992-2 only. CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF -60 -80 CLOAD = 10pF 50pF 100pF 500pF 1000pF 5000pF 10000pF -100 -120 -140 -160 -180 100 1000 FREQUENCY (kHz) 10 10000 1992 G60 100 FREQUENCY (kHz) 1000 1992 G62 1992 G61 Differential Gain Error vs Temperature VOCM Gain vs Frequency, VS = 2.5V 0.05 5 0.04 CLOAD = 10pF TO 10000pF 0 -5 0.02 0.01 GAIN (dB) GAIN ERROR (%) 0.03 0 -0.01 -0.02 -10 -15 -20 -0.03 -25 -0.04 -0.05 -50 -30 -25 50 25 0 75 TEMPERATURE (C) 100 125 10 100 1000 FREQUENCY (kHz) 1992 G64 1992 G63 Differential Input Offset Voltage vs Input Common Mode Voltage (Note 7) Differential Input Offset Voltage vs Input Common Mode Voltage (Note 7) -40C 25C -0.5 85C 125C -1.0 1.0 -40C 0.5 85C 0 -0.5 25C 125C -1.0 -1.5 -1.5 -2.0 +VS = 5V 1.5 -VS = -5V VOCM = 0V DIFFERENTIAL VOS (mV) DIFFERENTIAL VOS (mV) DIFFERENTIAL VOS (mV) 1.0 0 2.0 +VS = 5V 1.5 -VS = 0V VOCM = 2.5V +VS = 2.7V -VS = 0V 1.5 VOCM = 1.35V 0.5 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 COMMON MODE VOLTAGE (V) 1992 G65 1.0 -40C 0.5 0 -0.5 85C 25C 125C -1.0 -1.5 -2.0 0 Differential Input Offset Voltage vs Input Common Mode Voltage (Note 7) 2.0 2.0 10000 -2.0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 COMMON MODE VOLTAGE (V) 1992 G66 -5 -4 -3 -2 -1 0 1 2 3 COMMON MODE VOLTAGE (V) 4 5 1992 G67 1992fb 15 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Differential Input Large-Signal Step Response 90 80 70 CMRR (dB) VOUTDIFF (1V/DIV) 100 +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 750mV -VIN = 750mV 0V Common Mode Rejection Ratio vs Frequency (Note 7) VOUTDIFF (1V/DIV) Differential Input Large-Signal Step Response +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 750mV -VIN = 750mV CLOAD = 0pF Applicable to the LTC1992-2 only. 0V 60 50 40 30 20 CLOAD = 10000pF CLOAD = 1000pF 2s/DIV 20s/DIV 1992 G68 VAMPCM VAMPDIFF 10 0 100 1992 G69 1k 10k 100k FREQUENCY (Hz) 1M 1992 G70 2.5V Power Supply Rejection Ratio vs Frequency (Note 7) 100 +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 2V -VIN = 1V 2.5V 90 -VS 80 +VS 70 PSRR (dB) +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 2V -VIN = 1V CLOAD = 0pF Single-Ended Input Large-Signal Step Response VOUTDIFF (1V/DIV) VOUTDIFF (1V/DIV) Single-Ended Input Large-Signal Step Response 60 50 40 30 20 CLOAD = 10000pF CLOAD = 1000pF 2s/DIV 0 20s/DIV 1992 G71 VS VAMPDIFF 10 1992 G72 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G73 +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 25mV -VIN = 25mV 0V Output Balance vs Frequency 0 -20 OUTPUT BALANCE (dB) 0V VOUTDIFF (50mV/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 25mV -VIN = 25mV CLOAD = 0pF Differential Input Small-Signal Step Response VOUTDIFF (50mV/DIV) Differential Input Small-Signal Step Response -40 -60 -80 CLOAD = 10000pF CLOAD = 1000pF VOUTCM VOUTDIFF -100 2s/DIV 1992 G74 20s/DIV 1992 G75 1 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G76 1992fb 16 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Small-Signal Step Response Applicable to the LTC1992-2 only. Single-Ended Input Small-Signal Step Response Differential Noise Voltage Density vs Frequency 1000 +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 100mV -VIN = 50mV CLOAD = 0pF 2s/DIV INPUT REFERRED NOISE (nVHz) VOUTDIFF (50mV/DIV) 2.5V 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 100mV -VIN = 50mV 10 20s/DIV 1992 G77 100 1992 G78 10 100 1000 FREQUENCY (Hz) 10000 1922 G79 THD + Noise vs Frequency THD + Noise vs Amplitude -40 -40 500kHz MEASUREMENT BANDWIDTH +VS = 5V -50 -VS = -5V VOCM = 0V 50kHz THD + NOISE (dB) -50 THD + NOISE (dB) VOUTDIFF (50mV/DIV) CLOAD = 10000pF CLOAD = 1000pF -60 -70 VOUT = 1VP-PDIFF VOUT = 2VP-PDIFF -80 -90 -100 100 VOUT = 5VP-PDIFF -60 20kHz -70 10kHz 5kHz -80 2kHz -90 VOUT = 10VP-PDIFF 1kHz -100 1k 10k FREQUENCY (Hz) 50k 1992 G80 0.1 1 INPUT SIGNAL AMPLITUDE (VP-PDIFF) 10 1992 G81 1992fb 17 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Differential Gain vs Frequency, VS = 2.5V CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF 100 1000 FREQUENCY (kHz) 30 24 18 12 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -54 -60 10000 0 -20 -40 CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF -80 CLOAD = 10pF 50pF 100pF 500pF 1000pF 5000pF 10000pF -100 -140 -160 -180 100 1000 FREQUENCY (kHz) 10 -60 -120 10 10000 1992 G82 100 FREQUENCY (kHz) 1992 G84 VOCM Gain vs Frequency 0.050 5 0.025 0 0 CLOAD = 10pF TO 10000pF -5 GAIN (dB) -0.025 -0.050 -10 -15 -0.075 -20 -0.100 -25 -0.125 -01.50 -50 -30 -25 50 25 0 75 TEMPERATURE (C) 100 10 125 100 1000 FREQUENCY (kHz) 10000 1992 G86 1992 G85 Differential Input Offset Voltage vs Input Common Mode Voltage Differential Input Offset Voltage vs Input Common Mode Voltage 1.0 0.5 -40C 0 125C 85C -1.0 1.5 1.0 0.5 DIFFERENTIAL VOS (mV) DIFFERENTIAL VOS (mV) DIFFERENTIAL VOS (mV) 2.0 +VS = 5V -VS = 0V 1.5 VOCM = 2.5V +VS = 2.7V -VS = 0V 1.5 VOCM = 1.35V 25C -40C 0 -0.5 25C 125C 85C -1.0 -1.5 -1.5 -2.0 -2.0 0 Differential Input Offset Voltage vs Input Common Mode Voltage 2.0 2.0 -0.5 1000 1992 G83 Differential Gain Error vs Temperature GAIN ERROR (%) Differential Phase Response vs Frequency PHASE (DEG) GAIN (dB) GAIN (dB) Differential Input Differential Gain vs Frequency, VS = 2.5V 30 24 18 12 6 0 -6 -12 -18 -24 -30 -36 -42 -48 -54 -60 10 Applicable to the LTC1992-5 only. 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 COMMON MODE VOLTAGE (V) 1922 G87 +VS = 5V -VS = -5V VOCM = 0V 1.0 0.5 0 -40C 85C 25C 125C -0.5 -1.0 -1.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 COMMON MODE VOLTAGE (V) 1922 G88 -2.0 -5 -4 -3 -2 -1 0 1 2 3 COMMON MODE VOLTAGE (V) 4 5 1922 G89 1992fb 18 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Common Mode Rejection Ratio vs Frequency (Note 7) 100 +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 300mV -VIN = 300mV 90 80 70 CMRR (dB) 0V VOUTDIFF (1V/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 300mV -VIN = 300mV CLOAD = 0pF Differential Input Large-Signal Step Response VOUTDIFF (1V/DIV) Differential Input Large-Signal Step Response Applicable to the LTC1992-5 only. 0V 60 50 40 30 20 CLOAD = 10000pF CLOAD = 1000pF 2s/DIV 20s/DIV 1992 G90 VAMPCM VAMPDIFF 10 0 100 1992 G91 1k 10k 100k FREQUENCY (Hz) 1M 1992 G92 Single-Ended Input Large-Signal Step Response Single-Ended Input Large-Signal Step Response Power Supply Rejection Ratio vs Frequency (Note 7) 100 CLOAD = 10000pF CLOAD = 1000pF 90 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 800mV -VIN = 400mV CLOAD = 0pF 70 PSRR (dB) VOUTDIFF (1V/DIV) VOUTDIFF (1V/DIV) 80 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 800mV -VIN = 400mV +VS 60 -VS 50 40 30 20 VS VAMPDIFF 10 0 2s/DIV 20s/DIV 1992 G93 1992 G94 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G95 +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 10mV -VIN = 10mV 0V Output Balance vs Frequency 0 -20 OUTPUT BALANCE (dB) 0V VOUTDIFF (50mV/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 10mV -VIN = 10mV CLOAD = 0pF Differential Input Small-Signal Step Response VOUTDIFF (50mV/DIV) Differential Input Small-Signal Step Response -40 -60 -80 VOUTCM VOUTDIFF CLOAD = 10000pF CLOAD = 1000pF 5s/DIV 1992 G96 50s/DIV 1992 G97 -100 1 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G98 1992fb 19 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Small-Signal Step Response Differential Noise Voltage Density vs Frequency VOUTDIFF (50mV/DIV) VOUTDIFF (50mV/DIV) CLOAD = 10000pF CLOAD = 1000pF 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 40mV -VIN = 20mV CLOAD = 0pF 5s/DIV 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 40mV -VIN = 20mV 100 10 50s/DIV 1992 G99 1000 INPUT REFERRED NOISE (nVHz) Single-Ended Input Small-Signal Step Response Applicable to the LTC1992-5 only. 1992 G100 10 100 1000 FREQUENCY (Hz) 10000 1922 G101 THD + Noise vs Frequency THD + Noise vs Amplitude -40 -40 -60 -70 THD + NOISE (dB) THD + NOISE (dB) 500kHz MEASUREMENT BANDWIDTH +VS = 5V -50 -VS = -5V VOCM = 0V VOUT = 1VP-PDIFF VOUT = 2VP-PDIFF VOUT = 5VP-PDIFF -80 VOUT = 10VP-PDIFF -90 -100 100 500kHz MEASUREMENT BANDWIDTH +VS = 5V -50 -VS = -5V VOCM = 0V 50kHz -60 20kHz -70 10kHz 5kHz 2kHz -80 -90 1kHz -100 1k 10k FREQUENCY (Hz) 50k 1992 G102 0.1 1 INPUT SIGNAL AMPLITUDE (VP-PDIFF) 5 1992 G103 1992fb 20 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Differential Gain vs Frequency, VS = 2.5V Differential Input Differential Gain vs Frequency, VS = 2.5V Differential Phase Response vs Frequency 40 0 30 -20 20 20 -40 10 10 0 0 -10 CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF -20 -30 -40 -50 -60 -10 CLOAD = 10000pF CLOAD = 5000pF CLOAD = 1000pF CLOAD = 500pF CLOAD = 100pF CLOAD = 50pF CLOAD = 10pF -20 -30 -40 -50 -60 100 1000 FREQUENCY (kHz) 10 10000 PHASE (DEG) 40 30 GAIN (dB) GAIN (dB) Applicable to the LTC1992-10 only. -80 CLOAD = 10pF 50pF 100pF 500pF 1000pF 5000pF 10000pF -100 -120 -140 -160 -180 100 1000 FREQUENCY (kHz) 10 -60 10 10000 1992 G104 100 FREQUENCY (kHz) 1000 1992 G106 1992 G105 Differential Gain Error vs Temperature VOCM Gain vs Frequency 5 0.050 0.025 CLOAD = 10pF TO 10000pF 0 -5 -0.025 -0.050 GAIN (dB) GAIN ERROR (%) 0 -0.075 -0.100 -0.125 -10 -15 -20 -0.150 -25 -0.175 -0.200 -50 -30 -25 50 25 0 75 TEMPERATURE (C) 100 10 125 100 1000 FREQUENCY (kHz) 1992 G108 1992 G107 Differential Input Offset Voltage vs Input Common Mode Voltage Differential Input Offset Voltage vs Input Common Mode Voltage 0.5 -40C 125C -0.5 25C 85C 1.0 0.5 0 -0.5 -1.5 -2.0 -2.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 COMMON MODE VOLTAGE (V) 1922 G109 -40C 125C 25C 85C -1.0 -1.5 0 1.5 DIFFERENTIAL VOS (mV) 1.0 -1.0 2.0 +VS = 5V 1.5 -VS = 0V VOCM = 2.5V DIFFERENTIAL VOS (mV) DIFFERENTIAL VOS (mV) +VS = 2.7V -VS = 0V 1.5 VOCM = 1.35V 0 Differential Input Offset Voltage vs Input Common Mode Voltage 2.0 2.0 10000 +VS = 5V -VS = -5V VOCM = 0V 1.0 0.5 -40C 0 -0.5 25C 85C 125C -1.0 -1.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 COMMON MODE VOLTAGE (V) 1922 G110 -2.0 -5 -4 -3 -2 -1 0 1 2 3 COMMON MODE VOLTAGE (V) 4 5 1922 G111 1992fb 21 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Common Mode Rejection Ratio vs Frequency (Note 7) 100 +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 150mV -VIN = 150mV 90 80 70 CMRR (dB) 0V VOUTDIFF (1V/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 150mV -VIN = 150mV CLOAD = 0pF Differential Input Large-Signal Step Response VOUTDIFF (1V/DIV) Differential Input Large-Signal Step Response Applicable to the LTC1992-10 only. 0V 60 50 40 30 20 CLOAD = 10000pF CLOAD = 1000pF 2s/DIV 20s/DIV 1992 G112 VAMPCM VAMPDIFF 10 0 100 1992 G113 1k 10k 100k FREQUENCY (Hz) 1M 1992 G114 Single-Ended Input Large-Signal Step Response Single-Ended Input Large-Signal Step Response Power Supply Rejection Ratio vs Frequency (Note 7) 100 CLOAD = 10000pF CLOAD = 1000pF 90 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 400mV -VIN = 200mV CLOAD = 0pF 2s/DIV +VS 70 PSRR (dB) VOUTDIFF (1V/DIV) VOUTDIFF (1V/DIV) 80 2.5V 20s/DIV 50 40 30 +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 400mV -VIN = 200mV 1992 G115 -VS 60 20 VS VAMPDIFF 10 0 1992 G116 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G117 +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 5mV -VIN = 5mV 0V 1992 G118 100s/DIV -20 -40 -60 -80 -100 CLOAD = 10000pF CLOAD = 1000pF 10s/DIV Output Balance vs Frequency 0 OUTPUT BALANCE (dB) 0V VOUTDIFF (50mV/DIV) +VS = 2.5V -VS = -2.5V VOCM = 0V +VIN = 5mV -VIN = 5mV CLOAD = 0pF Differential Input Small-Signal Step Response VOUTDIFF (50mV/DIV) Differential Input Small-Signal Step Response 1992 G119 VOUTCM VOUTDIFF -120 1 10 100 1k 10k FREQUENCY (Hz) 100k 1M 1992 G120 1992fb 22 LTC1992 Family TYPICAL PERFORMANCE CHARACTERISTICS Single-Ended Input Small-Signal Step Response Differential Noise Voltage Density vs Frequency VOUTDIFF (50mV/DIV) 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 20mV -VIN = 10mV CLOAD = 0pF 10s/DIV 2.5V +VS = 5V -VS = 0V VOCM = 2.5V +VIN = 0V TO 20mV -VIN = 10mV 100 10 100s/DIV 1992 G121 1000 10 1992 G122 100 1000 FREQUENCY (Hz) 10000 1922 G123 THD + Noise vs Frequency THD + Noise vs Amplitude -40 -40 500kHz MEASUREMENT BANDWIDTH +VS = 5V -50 -VS = -5V VOCM = 0V -60 -70 50kHz -50 THD + NOISE (dB) THD + NOISE (dB) VOUTDIFF (50mV/DIV) CLOAD = 10000pF CLOAD = 1000pF INPUT REFERRED NOISE (nVHz) Single-Ended Input Small-Signal Step Response Applicable to the LTC1992-10 only. VOUT = 1VP-PDIFF VOUT = 2VP-PDIFF VOUT = 5VP-PDIFF -80 -90 -100 100 20kHz -60 10kHz -70 5kHz 2kHz -80 1kHz -90 -100 1k 10k FREQUENCY (Hz) 50k 1992 G124 0.1 1 INPUT SIGNAL AMPLITUDE (VP-PDIFF) 2 1992 G125 1992fb 23 LTC1992 Family PIN FUNCTIONS -IN, +IN (Pins 1, 8): Inverting and Noninverting Inputs of the Amplifier. For the LTC1992 part, these pins are connected directly to the amplifier's P-channel MOSFET input devices. The fixed gain LTC1992-X parts have precision, on-chip gain setting resistors. The input resistors are nominally 30k for the LTC1992-1, LTC1992-2 and LTC1992-5 parts. The input resistors are nominally 15k for the LTC1992-10 part. +VS, -VS (Pins 3, 6): The +VS and -VS power supply pins should be bypassed with 0.1F capacitors to an adequate analog ground or ground plane. The bypass capacitors should be located as closely as possible to the supply pins. +OUT, -OUT (Pins 4, 5): The Positive and Negative Outputs of the Amplifier. These rail-to-rail outputs are designed to drive capacitive loads as high as 10,000pF. VMID (Pin 7): Mid-Supply Reference. This pin is connected to an on-chip resistive voltage divider to provide a midsupply reference. This provides a convenient way to set the output common mode level at half-supply. If used for this purpose, Pin 2 will be shorted to Pin 7, Pin 7 should be bypassed with a 0.1F capacitor to ground. If this reference voltage is not used, leave the pin floating. VOCM (Pin 2): Output Common Mode Voltage Set Pin. The voltage on this pin sets the output signal's common mode voltage level. The output common mode level is set independent of the input common mode level. This is a high impedance input and must be connected to a known and controlled voltage. It must never be left floating. BLOCK DIAGRAMS (1992) +VS 3 +VS -IN 1 V+ + 200k -VS 4 +OUT + 30k VMID 7 200k - V- + - A1 A2 + 30k VOCM 2 + +VS 5 -OUT - 1992 BD +IN 8 -VS 6 -VS 1992fb 24 LTC1992 Family BLOCK DIAGRAMS (1992-X) +VS 3 +VS -IN RIN RFB 1 200k -VS VMID +VS RIN PART LTC1992-1 LTC1992-2 LTC1992-5 LTC1992-10 RIN 4 +OUT + - 5 -OUT 7 200k +IN - + RFB 8 RFB 30k 30k 30k 60k 30k 150k 15k 150k -VS 6 -VS 2 VOCM 1992-X BD APPLICATIONS INFORMATION Theory of Operation The LTC1992 family consists of five fully differential, low power amplifiers. The LTC1992 is an unconstrained fully differential amplifier. The LTC1992-1, LTC1992-2, LTC19925 and LTC1992-10 are fixed gain blocks (with gains of 1, 2, 5 and 10 respectively) featuring precision on-chip resistors for accurate and ultra stable gain. In many ways, a fully differential amplifier functions much like the familiar, ubiquitous op amp. However, there are several key areas where the two differ. Referring to Figure 1, an op amp has a differential input, a high open-loop gain and utilizes negative feedback (through resistors) to set the closed-loop gain and thus control the amplifier's gain with great precision. A fully differential amplifier has all of these features plus an additional input and a complementary output. The complementary output reacts to the input signal in the same manner as the other output, but in the opposite direction. Two outputs changing in an equal but opposite manner require a common reference point (i.e., opposite relative to what?). The additional input, the VOCM pin, sets this reference point. The voltage on the VOCM input directly sets the output signal's common mode voltage and allows the output signal's common mode voltage to be set completely independent of the input signal's common mode voltage. Uncoupling the input and output common mode voltages makes signal level shifting easy. For a better understanding of the operation of a fully differential amplifier, refer to Figure 2. Here, the LTC1992 functional block diagram adds external resistors to realize a basic gain block. Note that the LTC1992 functional block diagram is not an exact replica of the LTC1992 circuitry. However, the Block Diagram is correct and is a very good tool for understanding the operation of fully differential amplifier circuits. Basic op amp fundamentals together with this block diagram provide all of the tools needed for understanding fully differential amplifier circuit applications. The LTC1992 Block Diagram has two op amps, two summing blocks (pay close attention the signs) and four resistors. Two resistors, RMID1 and RMID2, connect directly to the VMID pin and simply provide a convenient mid-supply reference. Its use is optional and it is not involved in the operation of the LTC1992's amplifier. The LTC1992 functions through the use of two servo networks each employing 1992fb 25 LTC1992 Family APPLICATIONS INFORMATION Op Amp -IN Fully Differential Amplifier - -IN LTC1992 AO +IN VOCM OUT + +IN * DIFFERENTIAL INPUT * HIGH OPEN-LOOP GAIN * SINGLE-ENDED OUTPUT * * * * Op Amp with Negative Feedback - + + - RIN Fully Differential Amplifier with Negative Feedback RFB RIN - - -VIN LTC1992 + +VOUT VOCM -VOUT VOCM LTC1992 VOUT RIN + -OUT DIFFERENTIAL INPUT HIGH OPEN-LOOP GAIN DIFFERENTIAL OUTPUT VOCM INPUT SETS OUTPUT COMMON MODE LEVEL RFB VIN +OUT LTC1992 AO - + +VIN R GAIN = - FB RIN VOCM R GAIN = - FB RIN RFB 1992 F01 Figure 1. Comparison of an Op Amp and a Fully Differential Amplifier RFB +VS 3 LTC1992 RIN +VIN -IN 1 INM V+ + RMID1 200k SP 4 + V- - + - A1 A2 VOCM 2 + RCMM 30k + - RIN -VIN +IN 8 INP +VOUT RCMP 30k VMID 7 RMID2 200k +OUT 5 -OUT -VOUT SM 6 -VS RFB 1992 F02 Figure 2. LTC1992 Functional Block Diagram with External Gain Setting Resistors 1992fb 26 LTC1992 Family APPLICATIONS INFORMATION negative feedback and using an op amp's differential input to create the servo's summing junction. One servo controls the signal gain path. The differential input of op amp A1 creates the summing junction of this servo. Any voltage present at the input of A1 is amplified (by the op amp's large open-loop gain), sent to the summing blocks and then onto the outputs. Taking note of the signs on the summing blocks, op amp A1's output moves +OUT and -OUT in opposite directions. Applying a voltage step at the INM node increases the +OUT voltage while the -OUT voltage decreases. The RFB resistors connect the outputs to the appropriate inputs establishing negative feedback and closing the servo's loop. Any servo loop always attempts to drive its error voltage to zero. In this servo, the error voltage is the voltage between the INM and INP nodes, thus A1 will force the voltages on the INP and INM nodes to be equal (within the part's DC offset, open loop gain and bandwidth limits). The "virtual short" between the two inputs is conceptually the same as that for op amps and is critical to understanding fully differential amplifier applications. The other servo controls the output common mode level. The differential input of op amp A2 creates the summing junction of this servo. Similar to the signal gain servo above, any voltage present at the input of A2 is amplified, sent to the summing blocks and then onto the outputs. However, in this case, both outputs move in the same direction. The resistors RCMP and RCMM connect the +OUT and -OUT outputs to A2's inverting input establishing negative feedback and closing the servo's loop. The midpoint of resistors RCMP and RCMM derives the output's common mode level (i.e., its average). This measure of the output's common mode level connects to A2's inverting input while A2's noninverting input connects directly to the VOCM pin. A2 forces the voltages on its inverting and noninverting inputs to be equal. In other words, it forces the output common mode voltage to be equal to the voltage on the VOCM input pin. For any fully differential amplifier application to function properly both the signal gain servo and the common mode level servo must be satisfied. When analyzing an applications circuit, the INP node voltage must equal the INM node voltage and the output common mode voltage must equal the VOCM voltage. If either of these servos is taken out of the specified areas of operation (e.g., inputs taken beyond the common mode range specifications, outputs hitting the supply rails or input signals varying faster than the part can track), the circuit will not function properly. Fully Differential Amplifier Signal Conventions Fully differential amplifiers have a multitude of signals and signal ranges to consider. To maintain proper operation with conventional op amps, the op amp's inputs and its output must not hit the supply rails and the input signal's common mode level must also be within the part's specified limits. These considerations also apply to fully differential amplifiers, but here there is an additional output to consider and common mode level shifting complicates matters. Figure 3 provides a list of the many signals and specifications as well as the naming convention. The phrase "common mode" appears in many places and often leads to confusion. The fully differential amplifier's ability to uncouple input and output common mode levels yields great design flexibility, but also complicates matters some. For simplicity, the equations in Figure 3 also assume an ideal amplifier and perfect resistor matching. For a detailed analysis, consult the fully differential amplifier applications circuit analysis section. Basic Applications Circuits Most fully differential amplifier applications circuits employ symmetrical feedback networks and are familiar territory for op amp users. Symmetrical feedback networks require that the -VIN/+VOUT network is a mirror image duplicate of the +VIN/-VOUT network. Each of these half circuits is basically just a standard inverting gain op amp circuit. Figure 4 shows three basic inverting gain op amp circuits and their corresponding fully differential amplifier cousins. The vast majority of fully differential amplifier circuits derive from old tried and true inverting op amp circuits. To create a fully differential amplifier circuit from an inverting op amp circuit, first simply transfer the op amp's VIN/VOUT network to the fully differential amplifier's -VIN/+VOUT nodes. Then, take a mirror image duplicate of the network and apply it to the fully differential amplifier's +VIN/-VOUT nodes. Op amp users can comfortably transfer any inverting op amp circuit to a fully differential amplifier in this manner. 1992fb 27 LTC1992 Family APPLICATIONS INFORMATION RFB RIN A INM 2AVP-P -VIN -A VINDIFF 4AVP-PDIFF RIN 2AVP-P +VIN -A + +VOUT VOCM LTC1992 VOCM VINCM A - INP B -B 2BVP-P VOUTDIFF 4BVP-PDIFF VOUTCM + - -VOUT B -B 2BVP-P RFB 1992 F03 DIFFERENTIAL = V INDIFF = +VIN - -VIN INPUT VOLTAGE DIFFERENTIAL = VOUTDIFF = +VOUT - -VOUT OUTPUT VOLTAGE +VIN + -VIN INPUT COMMON = V INCM = 2 MODE VOLTAGE +VOUT + -VOUT OUTPUT COMMON = V OUTCM = 2 MODE VOLTAGE ( ( ) ) +VOUT = +VIN - -VIN * 1 RFB * + VOCM 2 RIN ; VOSCM = 0V -VOUT = -VIN - +VIN * 1 RFB * + VOCM 2 RIN ; VOSCM = 0V RFB VOUTDIFF = VINDIFF * R IN VAMPDIFF = VINP - VINM VAMPCM = VINP + VINM 2 VOUTCM = VOCM CMRR = VAMPCM ; +VIN = -VIN VAMPDIFF OUTPUT BALANCE = eNOUT = ( VOUTCM VOUTDIFF ) RFB + 1 * eNIN2 + rN2 WHERE: eNOUT = OUTPUT REFERRED NOISE VOLTAGE DENSITY RIN eNIN = INPUT REFERRED NOISE VOLTAGE DENSITY ( ) RIN * RFB rN (0.13nV/Hz) R + R IN FB (RESISTIVE NOISE IS ALREADY INCLUDED IN THE SPECIFICATIONS FOR THE FIXED GAIN LTC1992-X PARTS) VOSDIFFOUT = VOSDIFFIN * ( ) RFB +1 RIN VOSCM = VOUTCM - VOCM Figure 3. Fully Differential Amplifier Signal Conventions (Ideal Amplifier and Perfect Resistor Matching is Assumed) Single-Ended to Differential Conversion One of the most important applications of fully differential amplifiers is single-ended signaling to differential signaling conversion. Many systems have a single-ended signal that must connect to an ADC with a differential input. The ADC could be run in a single-ended manner, but performance usually degrades. Fortunately, all of basic applications circuits shown in Figure 4, as well as all of the fixed gain LTC1992-X parts, are equally suitable for both differential and single-ended input signals. For single-ended input signals, connect one of the inputs to a reference voltage (e.g., ground or mid-supply) and connect the other to the signal path. There are no tradeoffs here as the part's performance is the same with single-ended or differential input signals. Which input is used for the signal path only affects the polarity of the differential output signal. Signal Level Shifting Another important application of fully differential amplifier is signal level shifting. Single-ended to differential conversion accompanied by a signal level shift is very commonplace when driving ADCs. As noted in the theory of operation section, fully differential amplifiers have a common mode level servo that determines the output common mode level independent of the input common mode level. To set the output common mode level, simply apply the desired voltage to the VOCM input pin. The voltage range on the VOCM pin is from (-VS + 0.5V) to (+VS - 1.3V). 1992fb 28 LTC1992 Family APPLICATIONS INFORMATION Gain Block RFB RIN RIN - VIN RFB VOUT + + - +VIN R GAIN = FB RIN CIN AC Coupled Gain Block - RFB RIN VOUT CIN + - +VIN RIN -VOUT RFB Single Pole Lowpass Filter C RFB RFB RIN - VIN +VOUT VOCM LTC1992 RIN S H(S) = HO * S + WP R 1 HO = FB ; WP = RIN RIN * CIN C + - -VIN + -VOUT RFB CIN RIN VIN +VOUT VOCM LTC1992 RIN RFB + - -VIN VOUT + + - +VIN WP S + WP RFB RFB 1 ;W = RIN P RFB * C C H(S) = HO * 3-Pole Lowpass Filter R2 +VOUT VOCM LTC1992 RIN WHERE HO = + - -VIN -VOUT R2 C1 R1 R3 VIN C1 - R1 R3 R1 C2 2 R3 -VIN R4 C2 VOUT C3 + +VIN - R4 + +VOUT C3 2 VOCM LTC1992 R4 + - -VOUT C1 H(S) = HO ( )( WP S + WP WO2 WO S2 + S + WO2 Q WHERE HO = R2 ; WP = 1 ; WO = R4C3 R1 Q= R1 * R2R3 * R1 R2 + R1 R2 + R2 R3 ) R2 1992 F04 1 R2R3C1C2 C2 C1 Figure 4. Basic Fully Differential Amplifier Application Circuits (Note: Single-Ended to Differential Conversion is Easily Accomplished by Connecting One of the Input Nodes, +VIN or -VIN, to a DC Reference Level (e.g., Ground)) 1992fb 29 LTC1992 Family APPLICATIONS INFORMATION The VOCM input pin has a very high input impedance and is easily driven by even the weakest of sources. Many ADCs provide a voltage reference output that defines either its common mode level or its full-scale level. Apply the ADC's reference potential either directly to the VOCM pin or through a resistive voltage divider depending on the reference voltage's definition. When controlling the VOCM pin by a high impedance source, connect a bypass capacitor (1000pF to 0.1F) from the VOCM pin to ground to lower the high frequency impedance and limit external noise coupling. Other applications will want the output biased at a midpoint of the power supplies for maximum output voltage swing. For these applications, the LTC1992 provides a mid-supply potential at the VMID pin. The VMID pin connects to a simple resistive voltage divider with two 200k resistors connected between the supply pins. To use this feature, connect the VMID pin to the VOCM pin and bypass this node with a capacitor. One undesired effect of utilizing the level shifting function is an increase in the differential output offset voltage due to gain setting resistor mismatch. The offset is approximately the amount of level shift (VOUTCM - VINCM) multiplied by the amount of resistor mismatch. For example, a 2V level shift with 0.1% resistors will give around 2mV of output offset (2 * 0.1% = 2mV). The exact amount of offset is dependent on the application's gain and the resistor mismatch. For a detail description, consult the Fully Differential Amplifier Applications Circuit Analysis section. CMRR and Output Balance low frequency CMRR performance. The specifications for the fixed gain LTC1992-X parts include the on-chip resistor matching effects. Also, note that an input common mode signal appears as a differential output signal reduced by the CMRR. As with op amps, at higher frequencies the CMRR degrades. Refer to the Typical Performance plots for the details of the CMRR performance over frequency. At low frequencies, the output balance specification is determined by the matching of the on-chip RCMM and RCMP resistors. At higher frequencies, the output balance degrades. Refer to the typical performance plots for the details of the output balance performance over frequency. Input Impedance The input impedance for a fully differential amplifier application circuit is similar to that of a standard op amp inverting amplifier. One major difference is that the input impedance is different for differential input signals and single-ended signals. Referring to Figure 3, for differential input signals the input impedance is expressed by the following expression: RINDIFF = 2 * RIN For single-ended signals, the input impedance is expressed by the following expression: RINS-E = RIN RFB 1- 2 * (RIN + RFB ) One common misconception of fully differential amplifiers is that the common mode level servo guarantees an infinite common mode rejection ratio (CMRR). This is not true. The common mode level servo does, however, force the two outputs to be truly complementary (i.e., exactly opposite or 180 degrees out of phase). Output balance is a measure of how complementary the two outputs are. The input impedance for single-ended signals is slightly higher than the RIN value since some of the input signal is fed back and appears as the amplifier's input common mode level. This small amount of positive feedback increases the input impedance. At low frequencies, CMRR is primarily determined by the matching of the gain setting resistors. Like any op amp, the LTC1992 does not have infinite CMRR, however resistor mismatching of only 0.018%, halves the circuit's CMRR. Standard 1% tolerance resistors yield a CMRR of about 40dB. For most applications, resistor matching dominates The LTC1992 family of parts is stable for all capacitive loads up to at least 10,000pF. While stability is guaranteed, the part's performance is not unaffected by capacitive loading. Large capacitive loads increase output step response ringing and settling time, decrease the bandwidth and increase the frequency response peaking. Refer to the Driving Capacitive Loads 1992fb 30 LTC1992 Family APPLICATIONS INFORMATION Typical Performance plots for small-signal step response, large-signal step response and gain over frequency to appraise the effects of capacitive loading. While the consequences are minor in most instances, consider these effects when designing application circuits with large capacitive loads. Input Signal Amplitude Considerations For application circuits to operate correctly, the amplifier must be in its linear operating range. To be in the linear operating range, the input signal's common mode voltage must be within the part's specified limits and the rail-to-rail outputs must stay within the supply voltage rails. Additionally, the fixed gain LTC1992-X parts have input protection diodes that limit the input signal to be within the supply voltage rails. The unconstrained LTC1992 uses external resistors allowing the source signals to go beyond the supply voltage rails. When taken outside of the linear operating range, the circuit does not perform as expected, however nothing extreme occurs. Outputs driven into the supply voltage rails are simply clipped. There is no phase reversal or oscillation. Once the outputs return to the linear operating range, there is a small recovery time, then normal operation proceeds. When the input common mode voltage is below the specified lower limit, on-chip protection diodes conduct and clamp the signal. Once the signal returns to the specified operating range, normal operation proceeds. If the input common mode voltage goes slightly above the specified upper limit (by no more than about 500mV), the amplifier's open-loop gain reduces and DC offset and closed-loop gain errors increase. Return the input back to the specified range and normal performance commences. If taken well above the upper limit, the amplifier's input stage is cut off. The gain servo is now open loop; however, the common mode servo is still functional. Output balance is maintained and the outputs go to opposite supply rails. However, which output goes to which supply rail is random. Once the input returns to the specified input common mode range, there is a small recovery time then normal operation proceeds. The LTC1992's input signal common mode range (VINCMR) is from (-VS - 0.1V) to (+VS - 1.3V). This specification applies to the voltage at the amplifier's input, the INP and INM nodes of Figure 2. The specifications for the fixed gain LTC1992-X parts reflect a higher maximum limit as this specification is for the entire gain block and references the signal at the input resistors. Differential input signals and single-ended signals require a slightly different set of formulae. Differential signals separate very nicely into common mode and differential components while single ended signals do not. Refer to Figure 5 for the formulae for calculating the available signal range. Additionally, Table 1 lists some common configurations and their appropriate signal levels. The LTC1992's outputs allow rail-to-rail signal swings. The output voltage on either output is a function of the input signal's amplitude, the gain configured and the output signal's common mode level set by the VOCM pin. For maximum signal swing, the VOCM pin is set at the midpoint of the supply voltages. For other applications, such as an ADC driver, the required level must fall within the VOCM range of (-VS + 0.5V) to (+VS - 1.3V). For single-ended input signals, it is not always obvious which output will clip first thus both outputs are calculated and the minimum value determines the signal limit. Refer to Figure 5 for the formula and Table 1 for examples. To ensure proper linear operation both the input common mode level and the output signal level must be within the specified limits. These same criteria are also present with standard op amps. However, with a fully differential amplifier, it is a bit more complex and old familiar op amp intuition often leads to the wrong result. This is especially true for single-ended to differential conversion with level shifting. The required calculations are a bit tedious, but are necessary to guarantee proper linear operation. 1992fb 31 LTC1992 Family APPLICATIONS INFORMATION Differential Input Signals RFB A 2AVP-P -VIN -A VINDIFF 4AVP-PDIFF INM RIN NODE - RIN A 2AVP-P +VIN -A -B 2BVP-P VOUTDIFF 4BVP-PDIFF VOUTCM + - INP NODE B +VOUT VOCM LTC1992 VOCM VINCM + -VOUT B -B 2BVP-P R G = FB RIN RFB INPUT COMMON MODE LIMITS A. CALCULATE VINCM MINIMUM AND MAXIMUM GIVEN RIN, RFB AND VOCM 1 VINCM(MAX) = (+VS - 1.3V) + (+VS - 1.3V - VOCM) G 1 VINCM(MIN) = (-VS - 0.1V) + (-VS - 0.1V - VOCM) G OR B. WITH A KNOWN VINCM, RIN, RFB AND VOCM, CALCULATE COMMON MODE VOLTAGE AT INP AND INM NODES (VINCM(AMP)) AND CHECK THAT IT IS WITHIN THE SPECIFIED LIMITS. V + VINM 1 G VINCM(AMP) = INP = V + V 2 G + 1 INCM G + 1 OCM OUTPUT SIGNAL CLIPPING LIMIT VINDIFF(MAX)(VP-PDIFF) = THE LESSER VALUE OF 4 4 (+VS - VOCM) OR (V - -VS) G G OCM Single-Ended Input Signals RFB INM RIN NODE - VINREF VREF -A 2AVP-P VINSIG +VOUT VOCM LTC1992 VOCM RIN A + + - INP NODE B -B 2BVP-P VOUTDIFF 4BVP-PDIFF VOUTCM -VOUT B -B 2BVP-P R G = FB RIN RFB INPUT COMMON MODE LIMITS (NOTE: FOR THE FIXED GAIN LTC1992-X PARTS, VINREF AND VINSIG CANNOT EXCEED THE SUPPLIES) VINSIG(MAX) = 2 VINSIG(MIN) = 2 OR VINSIGP-P = 2 ( ( ( ) ( ) ( ) ( V 1 +VS - 1.3V - INREF + +VS - 1.3V - VOCM 2 G V 1 -VS - 0.1V - INREF + -VS - 0.1V - VOCM 2 G (+VS - -VS) - 1.2V + ) ) ) 1 (+VS - -VS) - 1.2V G OUTPUT SIGNAL CLIPPING LIMIT VINSIG(MAX) = THE LESSER VALUE OF VINREF + 2 2 (+VS - VOCM) OR VINREF + (V - -VS) G G OCM VINSIG(MIN) = THE GREATER VALUE OF VINREF + 2 2 (-VS - VOCM) OR VINREF + (V - +VS) G G OCM 1992 F05 Figure 5. Input Signal Limitations 1992fb 32 LTC1992 Family APPLICATIONS INFORMATION Table 1. Input Signal Limitations for Some Common Applications Differential Input Signal, VOCM at Mid-Supply. (VINCM must be within the Min and Max table values and VINDIFF must be less than the table value) +VS (V) -VS (V) GAIN (V/V) VOCM (V) VINCM(MAX) (V) VINCM(MIN) (V) VINDIFF(MAX) (VP-PDIFF) VOUTDIFF(MAX) (VP-PDIFF) 2.7 0 1 1.35 1.450 -1.550 5.40 5.40 2.7 0 2 1.35 1.425 -0.825 2.70 5.40 2.7 0 5 1.35 1.410 -0.390 1.08 5.40 2.7 0 10 1.35 1.405 -0.245 0.54 5.40 5 0 1 2.5 4.900 -2.700 10.00 10.00 5 0 2 2.5 4.300 -1.400 5.00 10.00 5 0 5 2.5 3.940 -0.620 2.00 10.00 5 0 10 2.5 3.820 -0.360 1.00 10.00 5 -5 1 0 7.400 -10.200 20.00 20.00 5 -5 2 0 5.550 -7.650 10.00 20.00 5 -5 5 0 4.440 -6.120 4.00 20.00 5 -5 10 0 4.070 -5.610 2.00 20.00 Differential Input Signal, VOCM at Typical ADC Levels. (VINCM must be within the Min and Max table values and VINDIFF must be less than the table value) +VS (V) -VS (V) GAIN (V/V) VOCM (V) VINCM(MAX) (V) VINCM(MIN) (V) VINDIFF(MAX) (VP-PDIFF) VOUTDIFF(MAX) (VP-PDIFF) 2.7 0 1 1 1.800 -1.200 4.00 4.00 2.7 0 2 1 1.600 -0.650 2.00 4.00 2.7 0 5 1 1.480 -0.320 0.80 4.00 2.7 0 10 1 1.440 -0.210 0.40 4.00 5 0 1 2 5.400 -2.200 8.00 8.00 5 0 2 2 4.550 -1.150 4.00 8.00 5 0 5 2 4.040 -0.520 1.60 8.00 5 0 10 2 3.870 -0.310 0.80 8.00 5 -5 1 2 5.400 -12.200 12.00 12.00 5 -5 2 2 4.550 -8.650 6.00 12.00 5 -5 5 2 4.040 -6.520 2.40 12.00 5 -5 10 2 3.870 -5.810 1.20 12.00 1992fb 33 LTC1992 Family APPLICATIONS INFORMATION Table 1. Input Signal Limitations for Some Common Applications Mid-Supply Referenced Single-Ended Input Signal, VOCM at Mid-Supply. (The VINSIG Min and Max values listed account for both the input common mode limits and the output clipping) +VS (V) -VS (V) GAIN (V/V) VOCM (V) VINREF (V) VINSIG(MAX) (V) VINSIG(MIN) (V) VINSIGP-P(MAX) (VP-P AROUND VINREF) VOUTDIFF(MAX) (VP-PDIFF) 2.7 0 1 1.35 1.35 1.550 -1.350 0.40 0.40 2.7 0 2 1.35 1.35 1.500 0.000 0.30 0.60 2.7 0 5 1.35 1.35 1.470 0.810 0.24 1.20 2.7 0 10 1.35 1.35 1.460 1.080 0.22 2.20 5 0 1 2.5 2.5 7.300 -2.500 9.60 9.60 5 0 2 2.5 2.5 5.000 0.000 5.00 10.00 5 0 5 2.5 2.5 3.500 1.500 2.00 10.00 5 0 10 2.5 2.5 3.000 2.000 1.00 10.00 5 -5 1 0 0 10.000 -10.000 20.00 20.00 5 -5 2 0 0 5.000 -5.000 10.00 20.00 5 -5 5 0 0 2.000 -2.000 4.00 20.00 5 -5 10 0 0 1.000 -1.000 2.00 20.00 Mid-Supply Referenced Single-Ended Input Signal, VOCM at Typical ADC Levels. (The VINSIG Min and Max values listed account for both the input common mode limits and the output clipping) +VS (V) -VS (V) GAIN (V/V) VOCM (V) VINREF (V) VINSIG(MAX) (V) VINSIG(MIN) (V) VINSIGP-P(MAX) (VP-P AROUND VINREF) VOUTDIFF(MAX) (VP-PDIFF) 2.7 0 1 1 1.35 2.250 -0.650 1.80 1.80 2.7 0 2 1 1.35 1.850 0.350 1.00 2.00 2.7 0 5 1 1.35 1.610 0.950 0.52 2.60 2.7 0 10 1 1.35 1.530 1.150 0.36 3.60 5 0 1 2 2.5 6.500 -1.500 8.00 8.00 5 0 2 2 2.5 4.500 0.500 4.00 8.00 5 0 5 2 2.5 3.300 1.700 1.60 8.00 5 0 10 2 2.5 2.900 2.100 0.80 8.00 5 -5 1 2 0 6.000 -6.000 12.00 12.00 5 -5 2 2 0 3.000 -3.000 6.00 12.00 5 -5 5 2 0 1.200 -1.200 2.40 12.00 5 -5 10 2 0 0.600 -0.600 1.20 12.00 1992fb 34 LTC1992 Family APPLICATIONS INFORMATION Table 1. Input Signal Limitations for Some Common Applications Single Supply Ground Referenced Single-Ended Input Signal, VOCM at Mid-Supply. (The VINSIG Min and Max values listed account for both the input common mode limits and the output clipping) +VS (V) -VS (V) GAIN (V/V) VOCM (V) VINREF (V) VINSIG(MAX) (V) VINSIG(MIN) (V) VINSIGP-P(MAX) (VP-P AROUND VINREF) VOUTDIFF(MAX) (VP-PDIFF) 2.7 0 1 1.35 0 2.700 -2.700 5.40 5.40 2.7 0 2 1.35 0 1.350 -1.350 2.70 5.40 2.7 0 5 1.35 0 0.540 -0.540 1.08 5.40 2.7 0 10 1.35 0 0.270 -0.270 0.54 5.40 5 0 1 2.5 0 5.000 -5.000 10.00 10.00 5 0 2 2.5 0 2.500 -2.500 5.00 10.00 5 0 5 2.5 0 1.000 -1.000 2.00 10.00 5 0 10 2.5 0 0.500 -0.500 1.00 10.00 Single Supply Ground Referenced Single-Ended Input Signal, VOCM at Typical ADC Reference Levels. (The VINSIG Min and Max values listed account for both the input common mode limits and the output clipping) +VS (V) -VS (V) GAIN (V/V) VOCM (V) VINREF (V) VINSIG(MAX) (V) VINSIG(MIN) (V) VINSIGP-P(MAX) (VP-P AROUND VINREF) VOUTDIFF(MAX) (VP-PDIFF) 2.7 0 1 1 0 2.000 -2.000 4.00 4.00 2.7 0 2 1 0 1.000 -1.000 2.00 4.00 2.7 0 5 1 0 0.400 -0.400 0.80 4.00 2.7 0 10 1 0 0.200 -0.200 0.40 4.00 5 0 1 2 0 4.000 -4.000 8.00 8.00 5 0 2 2 0 2.000 -2.000 4.00 8.00 5 0 5 2 0 0.800 -0.800 1.60 8.00 5 0 10 2 0 0.400 -0.400 0.80 8.00 Fully Differential Amplifier Applications Circuit Analysis All of the previous applications circuit discussions have assumed perfectly matched symmetrical feedback networks. To consider the effects of mismatched or asymmetrical feedback networks, the equations get a bit messier. Figure 6 lists the basic gain equation for the differential output voltage in terms of +VIN, -VIN, VOSDIFF, VOUTCM and the feedback factors 1 and 2. The feedback factors are simply the portion of the output that is fed back to the input summing junction by the RFB-RIN resistive voltage divider. 1 and 2 have the range of zero to one. The VOUTCM term also includes its offset voltage, VOSCM, and its gain mismatch term, KCM. The KCM term is determined by the matching of the on-chip RCMP and RCMM resistors in the common mode level servo (see Figure 2). While mathematically correct, the basic signal equation does not immediately yield any intuitive feel for fully differential amplifier application operation. However, by nulling out specific terms, some basic observations and sensitivities come forth. Setting 1 equal to 2, VOSDIFF to zero and VOUTCM to VOCM gives the old gain equation from Figure 3. The ground referenced, single-ended input signal equation yields the interesting result that the driven side feedback factor (1) has a very different sensitivity than the grounded side (2). The CMRR is twice the feedback factor difference divided by the feedback factor sum. The differential output offset voltage has two terms. The first term is determined by the input offset term, VOSDIFF, and the application's gain. Note that this term equates to the formula in Figure 3 when 1 equals 2. The amount of signal level shifting and the feedback factor mismatch determines the second term. This term 1992fb 35 LTC1992 Family APPLICATIONS INFORMATION RFB2 RIN2 VINDIFF +VIN - -VIN + - -VIN VOCM RIN1 +VOUT + - +VIN VOUTDIFF +VOUT - -VOUT VOCM LTC1992 -VOUT RFB1 VOUTDIFF = 2[+VIN * (1 - B1) - (-VIN) * (1 - B2)] + 2VOSDIFF + 2VOUTCM (B1 - B2) B1 + B2 WHERE: B1 = RIN1 RIN2 ; B2 = RIN1 + RFB1 RIN2 + RFB2 ; VOSDIFF = AMPLIFIER INPUT REFERRED OFFSET VOLTAGE VOUTCM = KCM * VOCM + VOSCM 0.999 < KCM < 1.001 * FOR GROUND REFERENCED, SINGLE-ENDED INPUT SIGNAL, LET +VIN = VINSIG AND -VIN = 0V VOUTDIFF = 2 * VINSIG * (1 - B1) + 2VOSDIFF + 2VOUTCM (B1 - B2) B1 + B2 * COMMON MODE REJECTION: SET +VIN = -VIN = VINCM, VOSDIFF = 0V, VOUTCM = 0V CMRR = VINCM B1 + B2 =2 ; OUTPUT REFERRED VOUTDIFF B2 - B1 * OUTPUT DC OFFSET VOLTAGE: SET +VIN = -VIN = VINCM VOSDIFFOUT = VOSDIFF B2 - B1 2 + (VOUTCM - VINCM) 2 B1 + B2 B1 + B2 1992 F06 Figure 6. Basic Equations for Mismatched or Asymmetrical Feedback Applications Circuits quantifies the undesired effect of signal level shifting discussed earlier in the Signal Level Shifting section. Asymmetrical Feedback Application Circuits The basic signal equation in Figure 6 also gives insight to another piece of intuition. The feedback factors may be deliberately set to different values. One interesting class of these application circuits sets one or both of the feedback factors to the extreme values of either zero or one. Figure 7 shows three such circuits. At first these application circuits may look to be unstable or open loop. It is the common mode feedback loop that enables these circuits to function. While they are useful circuits, they have some shortcomings that must be considered. First, due to the severe feedback factor asymmetry, the VOCM level influences the differential output voltage with about the same strength as the input signal. With this much gain in the VOCM path, differential output offset and noise increase. The large VOCM to VOUTDIFF gain also necessitates that these circuits are largely limited to dual, split supply voltage applications with a ground referenced input signal and a grounded VOCM pin. The top application circuit in Figure 7 yields a high input impedance, precision gain of 2 block without any external resistors. The on-chip common mode feedback servo resistors determine the gain precision (better than 0.1 percent). By using the -VOUT output alone, this circuit is also useful to get a precision, single-ended output, high input impedance inverter. To intuitively understand this circuit, consider it as a standard op amp voltage follower (delivered through the signal gain servo) with a complementary output (delivered through the common mode level servo). As usual, the amplifier's input common mode range must not be exceeded. As with a standard op amp voltage follower, the common mode signal seen at the amplifier's input is the input signal itself. This condition limits the input signal swing, as well as the output signal swing, to be the input signal common mode range specification. The middle circuit is largely the same as the first except that the noninverting amplifier path has gain. Note that 1992fb 36 LTC1992 Family APPLICATIONS INFORMATION - + VOCM VIN +VOUT VOUTDIFF = 2(+VIN - VOCM) -VOUT SETTING VOCM = 0V VOCM LTC1992 + - VOUTDIFF = 2VIN RIN RFB - + VOCM VIN VOCM ( VOUTDIFF = 2 +VIN 1 - VOCM B ) ;B= RIN RIN + RFB VOCM LTC1992 + - -VOUT - + +VOUT SETTING VOCM = 0V RFB 1 VOUTDIFF = 2VIN B = 2VIN 1 + R IN () ( ( VOUTDIFF = 2 +VIN 1-B + VOCM B ) ) ;B= RIN RIN + RFB VOCM LTC1992 RIN VIN +VOUT + - -VOUT RFB SETTING VOCM = 0V RFB 1-B VOUTDIFF = 2VIN B = 2VIN R IN ( ) ( ) 1992 F07 Figure 7. Asymmetrical Feedback Application Circuits (Most Suitable in Applications with Dual, Split Supplies (e.g., 5V), Ground Referenced Single-Ended Input Signals and VOCM Connected to Ground) once the VOCM voltage is set to zero, the gain formula is the same as a standard noninverting op amp circuit multiplied by two to account for the complementary output. Taking RFB to zero (i.e., taking to one) gives the same formula as the top circuit. As in the top circuit, this circuit is also useful as a single-ended output, high input impedance inverting gain block (this time with gain). The input common mode considerations are similar to the top circuit's, but are not nearly as constrained since there is now gain in the noninverting amplifier path. This circuit, with VOCM at ground, also permits a rail-to-rail output swing in most applications. The bottom circuit is another circuit that utilizes a standard op amp configuration with a complementary output. In this case, the standard op amp circuit has an inverting configuration. With VOCM at zero volts, the gain formula is the same as a standard inverting op amp circuit multiplied by two to account for the complementary output. This circuit does not have any common mode level constraints as the inverting input voltage sets the input common mode level. This circuit also delivers rail-to-rail output voltage swing without any concerns. 1992fb 37 LTC1992 Family TYPICAL APPLICATIONS Interfacing a Bipolar, Ground Referenced, Single-Ended Signal to a Unipolar Single Supply, Differential Input ADC (VIN = 0V Gives a Digital Mid-Scale Code) 5V 1F 0.1F 40k 10k 13.3k 3 10k 1 7 - + VMID 2 2.5V VIN -2.5V 10k VOCM 8 0V 2 +IN 100pF LTC1992 + - 5V 100 4 1 8 VREF VCC SCK LTC1864 100 3 5 CONV -IN 6 5 SERIAL DATA LINK GND 6 13.3k SDO 7 4 1992 TA02a 10k 0.1F 40k Compact, Unipolar Serial Data Conversion 5V 1F 3 0.1F 1 7 2.5V VIN 0V VMID 2 VOCM 8 100 4 - + 2 100pF LTC1992-2 + - +IN 1 8 VREF VCC SCK LTC1864 100 3 5 -IN SDO CONV 7 6 5 SERIAL DATA LINK GND 6 4 0.1F 1992 TA03a Zero Components, Single-Ended Adder/Subtracter +VS 0.1F VA VB VC 1 2 8 3 - + 4 V1 = VB + VC - VA VOCM LTC1992-2 + - 6 -VS 5 V2 = VB + VA - VC 0.1F 1992 TA04 1992fb 38 LTC1992 Family TYPICAL APPLICATIONS Single-Ended to Differential Conversion Driving an ADC 10F 2.2F 10 + 3 VREF 5V 10F + 36 AVDD 5V 35 9 AVDD 10F + 10 DVDD DGND SHDN 33 LTC1603 4 REFCOMP 5V + 7.5k 2.5V REF 1.75X 4.375V CONTROL LOGIC AND TIMING 47F 0.1F 100 LTC1992-1 VOCM + - 6 + 1 AIN 2 5 OGND 28 + 100pF AIN- - 100 16-BIT SAMPLING ADC AGND 5 0.1F AGND 6 OUTPUT BUFFERS B15 TO B0 AGND 7 8 D15 TO D0 5V OR 3V 10F 16-BIT PARALLEL BUS 11 TO 26 AGND VSS 1992 TA06a 34 -5V -5V + 10F FFT of the Output Data AMPLITUDE (dB) VIN 8 VMID 4 RD 30 BUSY 27 + 2 - + P CONTROL LINES OVDD 29 3 1 7 CS 32 CONVST 31 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 -140 fIN = 10.0099kHz fSAMPLE = 333kHz 0 SNR =85.3dB THD = -72.1dB SINAD = -72dB 10 20 30 40 50 60 70 80 90 100 FREQUENCY (kHz) 1992 TA06b 1992fb 39 LTC1992 Family PACKAGE DESCRIPTION MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660 Rev F) 3.00 p 0.102 (.118 p .004) (NOTE 3) 0.889 p 0.127 (.035 p .005) 0.254 (.010) 8 7 6 5 3.00 p 0.102 (.118 p .004) (NOTE 4) 4.90 p 0.152 (.193 p .006) DETAIL "A" 0.52 (.0205) REF 0o - 6o TYP GAUGE PLANE 5.23 (.206) MIN 1 3.20 - 3.45 (.126 - .136) 0.53 p 0.152 (.021 p .006) DETAIL "A" 0.42 p 0.038 (.0165 p .0015) TYP 0.65 (.0256) BSC 1.10 (.043) MAX 2 3 4 0.86 (.034) REF 0.18 (.007) RECOMMENDED SOLDER PAD LAYOUT 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 SEATING PLANE 0.22 - 0.38 (.009 - .015) TYP 0.65 (.0256) BSC 0.1016 p 0.0508 (.004 p .002) MSOP (MS8) 0307 REV F 1992fb 40 LTC1992 Family REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A 7/10 Updated Part Markings 2 B 6/11 Revised Features 1 Updated to Specified Temperature Range in Absolute Maximum Ratings and Order Information 2 Revised Block Diagram 24 Revised subtitle in Figure 5 of Applications Information section 32 1992fb 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 its circuits as described herein will not infringe on existing patent rights. 41 LTC1992 Family TYPICAL APPLICATION Balanced Frequency Converter (Suitable for Frequencies up to 50kHz) 60kHz LOW PASS FILTER SAMPLER 2kHz LOWPASS FILTER 5V 0.1F 9.53k 0.1F 0.1F 120pF 9.53k 8.87k 7 BNC 9.53k VINP 3 1 330pF 2 8.87k 8 75k 4 - + VMID 4 7 6 60.4k 1 7 13 1/2 LTC1043 + - 5 12 37.4k 180pF 2 60.4k 8 14 16 120pF 11 37.4k 8 LTC1992 VOCM 390pF V+ 9.53k 3 - + VMID VOCM + - 390pF 17 0.1F 0.1F 10k VOUTP LTC1992 6 CLK - V BNC 4 BNC VOUTM 5 75k 0.1F 0.1F VOCM 1992 TA05a -5V CLK VINP = 24kHz (1V/DIV) 0V CLK = 25kHz (LOGIC SQUARE WAVE) (5V/DIV) VOUTP = 1kHz (0.5V/DIV) VOUTM = 1kHz (0.5V/DIV) 0V 0V 0V 200s/DIV 1992 TA05b RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1167 Precision Instrumentation Amplifier Single Resistor Sets the Gain LT1990 High Voltage, Gain Selectable Difference Amplifier 250V Common Mode, Micropower, Selectable Gain = 1, 10 LT1991 Precision Gain Selectable Difference Amplifier Micropower, Pin Selectable Gain = -13 to 14 LT1995 High Speed Gain Selectable Difference Amplifier 30MHz, 1000V/s, Pin Selectable Gain = -7 to 8 LT6600-X Differential In/Out Amplifier Lowpass Filter Very Low Noise, Standard Differential Amplifier Pinout 1992fb 42 Linear Technology Corporation LT 0611 REV A * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com (c) LINEAR TECHNOLOGY CORPORATION 2005