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LT1990 250V Input Range G = 1, 10, Micropower, Difference Amplifier DESCRIPTIO
The LT(R)1990 is a micropower precision difference amplifier with a very high common mode input voltage range. It has pin selectable gains of 1 or 10. The LT1990 operates over a 250V common mode voltage range on a 15V supply. The inputs are fault protected from common mode voltage transients up to 350V and differential voltages up to 500V. The LT1990 is ideally suited for both high side and low side current or voltage monitoring. On a single 5V supply, the LT1990 has an adjustable 85V input range, 70dB min CMRR and draws less than 120A supply current. The rail-to-rail output maximizes the dynamic range, especially important for single supplies as low as 2.7V. The LT1990 is specified for single 3V, 5V and 15V supplies over both commercial and industrial temperature ranges. The LT1990 is available in the 8-pin SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S

Pin Selectable Gain of 1 or 10 High Common Mode Voltage Range: 85V Window (VS = 5V, 0V) 250V (VS = 15V) Common Mode Rejection Ratio: 70dB Min Input Protection to 350V Gain Error: 0.28% Max PSRR: 82dB Min High Input Impedance: 2M Differential, 500k Common Mode Micropower: 120A Max Supply Current Wide Supply Range: 2.7V to 36V -3dB Bandwidth: 100kHz Rail-to-Rail Output 8-Pin SO Package
FEATURES

Battery Cell Voltage Monitoring High Voltage Current Sensing Signal Acquisition in Noisy Environments Input Protection Fault Protected Front Ends Level Sensing Isolation
TYPICAL APPLICATIO
+VSOURCE
Full-Bridge Load Current Monitor
5V LT1990 900k 7 2 1M 100k 10k 8
-+
IL
RS 3 VREF = 1.5V 4 IN OUT LT6650 GND FB 54.9k 1nF 40k 40k 20k 1 1F
1990 TA01
1M
-12V VCM 73V VOUT = VREF (10 * IL * RS)
U
- +
U
U
6
VOUT
10k 900k 100k
5
1990f
1
LT1990
ABSOLUTE
(Notes 1, 2)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW REF 1 -IN 2 +IN 3 V- 4 8 7 6 5 GAIN1 V+ OUT GAIN2
Total Supply Voltage (V + to V -) ............................... 36V Input Voltage Range Continuous ...................................................... 250V Transient (0.1s) ............................................... 350V Differential ....................................................... 500V Output Short-Circuit Duration (Note 3) ............ Indefinite Operating Temperature Range (Note 4) ...-40C to 85C Specified Temperature Range (Note 5) ....-40C to 85C Storage Temperature Range .................. -65C to 150C Lead Temperature (Soldering, 10 sec.)................. 300C
LT1990CS8 LT1990IS8 LT1990ACS8 LT1990AIS8 S8 PART MARKING 1990 1990A 1990I 1990AI
S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 190C/W
3V/5V ELECTRICAL CHARACTERISTICS
VS = 3V, 0V; VS = 5V, 0V; RL = 10k, VCM = VREF = half supply, G = 1, 10, TA = 25C, unless otherwise noted. (Note 6)
SYMBOL G G PARAMETER Gain Gain Error CONDITIONS Pins 5 and 8 = Open Pins 5 and 8 = GND VOUT = 0.5V to (+Vs) -0.75V LT1990, G = 1 LT1990A, G = 1 G = 10, VS = 5V, 0V VS = 5V, 0V; VOUT = 0.5V to 4.25V G=1 G = 10 Guaranteed by CMRR VS = 3V, 0V; VREF = 1.25V VS = 5V, 0V; VREF = 1.25V VS = 5V, 0V; VREF = 2.5V VS = 3V, 0V (Note 7) VCM = -5V to 25V, VREF = 1.25V LT1990 LT1990A VS = 5V, 0V VCM = -5V to 80V, VREF = 1.25V LT1990 LT1990A VS = 5V, 0V (Note 7) VCM = -38V to 47V, VREF = 2.5V LT1990 LT1990A VOS en Offset Voltage, RTI Input Noise Voltage, RTI Noise Voltage Density, RTI G = 1, 10 fO = 0.1Hz to 10Hz fO = 1kHz -5 -5 -38 MIN TYP 1 10 0.4 0.07 0.2 0.001 0.01 0.6 0.28 0.8 0.005 % % % % % V V V MAX UNITS
GNL
Gain Nonlinearity
VCM
Input Voltage Range
25 80 47
CMRR
Common Mode Rejection Ratio RTI (Referred to Input)
60 70
68 75
60 70
68 75
60 70
68 75 0.8 22 1 3
VP-P V/Hz
1990f
2
U
dB dB dB dB dB dB mV
W
U
U
WW
W
LT1990
3V/5V ELECTRICAL CHARACTERISTICS
VS = 3V, 0V; VS = 5V, 0V; RL = 10k, VCM = VREF = half supply, G = 1, 10, TA = 25C, unless otherwise noted. (Note 6)
SYMBOL RIN PSRR IS VOL VOH PARAMETER Input Resistance Power Supply Rejection Ratio, RTI Minimum Supply Voltage Supply Current Output Voltage Swing LOW Output Voltage Swing HIGH CONDITIONS Differential Common Mode VS = 2.7V to 12.7V, VCM = VREF = 1.25V Guaranteed by PSRR (Note 8) -IN = V+, +IN = Half Supply (Note 8) -IN = 0V, +IN = Half Supply VS = 3V, 0V, Below V+ VS = 5V, 0V, Below V+ Short to GND (Note 9) Short to V+ (Note 9) G=1 G = 10 G = 1, VS = 5V, 0V, VOUT = 0.5V to 4.5V 4V Step, G = 1, VS = 5V, 0V 4 13 80 MIN TYP 2 0.5 92 2.4 105 30 100 120 8 20 100 6.5 0.5 45 1 0.0007 2.7 120 50 150 175 MAX UNITS M M dB V A mV mV mV mA mA kHz kHz V/s s
ISC BW SR AVREF
Output Short-Circuit Current Bandwidth (-3dB) Slew Rate Settling Time to 0.01% Reference Gain to Output
The denotes the specifications which apply over the temperature range of 0C TA 70C. VS = 3V, 0V; VS = 5V, 0V; RL = 10k, VCM = VREF = half supply, G = 1, 10, unless otherwise noted. (Notes 4, 6)
SYMBOL G PARAMETER Gain Error CONDITIONS VOUT = 0.5V to (+VS) - 0.75V LT1990, G = 1 LT1990A, G = 1 G = 10 G = 1 (Note 10) G = 10 (Note 10) Guaranteed by CMRR VS = 3V, 0V, VREF = 1.25V VS = 5V, 0V, VREF = 1.25V VS = 5V, 0V, VREF = 2.5V VS = 3V, 0V (Note 7) VCM = -5V to 25V, VREF = 1.25V LT1990 LT1990A VS = 5V, 0V VCM = -5V to 80V, VREF = 1.25V LT1990 LT1990A VS = 5V, 0V (Note 7) VCM = -38V to 47V, VREF = 2.5V LT1990 LT1990A VOS Input Offset Voltage, RTI VS = 3V, 0V G = 1, 10 VS = 5V, 0V G = 1, 10

MIN
TYP
MAX 0.65 0.33 0.90
UNITS % % % ppm/C ppm/C V V V
G/T VCM
Gain vs Temperature Input Voltage Range
2 7 -5 -5 -37
10 20 25 80 48
CMRR
Common Mode Rejection Ratio, RTI

58 68
dB dB

58 68
dB dB

58 68 4.1 4.1
dB dB mV mV
1990f
3
LT1990
3V/5V ELECTRICAL CHARACTERISTICS
The denotes the specifications which apply over the temperature range of 0C TA 70C. VS = 3V, 0V; VS = 5V, 0V; RL = 10k, VCM = VREF = half supply, G = 1, 10, unless otherwise noted. (Notes 4, 6)
SYMBOL VOS/T VOSH PSRR PARAMETER Input Offset Voltage Drift, RTI Input Offset Voltage Hysteresis, RTI Power Supply Rejection Ratio, RTI CONDITIONS (Note 10) (Note 11) VS = 2.7V to 12.7V VCM = VREF = 1.25V G = 1, 10 Guaranteed by PSRR (Note 8) -IN = V+, +IN = Half Supply (Note 8) -IN = 0V, +IN = Half Supply VS = 3V, 0V, Below V+ VS = 5V, 0V, Below V+ Short to GND (Note 9) Short to V+ (Note 9)

MIN
TYP 5 230
MAX 22
UNITS V/C V

78 2.7 150 60 180 205 3 11
dB V A mV mV mV mA mA
Minimum Supply Voltage IS VOL VOH Supply Current Output Voltage Swing LOW Output Voltage Swing HIGH
ISC
Output Short-Circuit Current
The denotes the specifications which apply over the temperature range of -40C TA 85C. VS = 3V, 0V; VS = 5V, 0V; RL = 10k, VCM = VREF = half supply, G = 1, 10, unless otherwise noted. (Notes 4, 6)
SYMBOL G PARAMETER Gain Error CONDITIONS VOUT = 0.5V to (+VS) - 0.75V LT1990, G = 1 LT1990A, G = 1 G = 10 G = 1 (Note 10) G = 10 (Note 10) Guaranteed by CMRR VS = 3V, 0V, VREF = 1.25V VS = 5V, 0V, VREF = 1.25V VS = 5V, 0V, VREF = 2.5V VS = 3V, 0V (Note 7) VCM = -5V to 25V, VREF = 1.25V LT1990 LT1990A VS = 5V, 0V VCM = -5V to 80V, VREF = 1.25V LT1990 LT1990A VS = 5V, 0V (Note 7) VCM = -38V to 47V, VREF = 2.5V LT1990 LT1990A VOS Input Offset Voltage, RTI VS = 3V, 0V G = 1, 10 VS = 5V, 0V G = 1, 10 VOS/T VOSH PSRR Input Offset Voltage Drift, RTI Input Offset Voltage Hysteresis, RTI Power Supply Rejection Ratio, RTI (Note 10) (Note 11) VS = 2.7V to 12.7V VCM = VREF = 1.25V

MIN
TYP
MAX 0.67 0.35 0.95
UNITS % % % ppm/C ppm/C V V V
G/T VCM
Gain vs Temperature Input Voltage Range
2 7 -5 -5 -37
10 20 25 80 48
CMRR
Common Mode Rejection Ratio, RTI

57 67
dB dB

57 67
dB dB

57 67 4.5 4.5 5 230 76 22
dB dB mV mV V/C V dB
1990f
4
LT1990
3V/5V ELECTRICAL CHARACTERISTICS
The denotes the specifications which apply over the temperature range of -40C TA 85C. VS = 3V, 0V; VS = 5V, 0V; RL = 10k, VCM = VREF = half supply, G = 1, 10, unless otherwise noted. (Notes 4, 6)
SYMBOL IS VOL VOH PARAMETER Minimum Supply Voltage Supply Current Output Voltage Swing LOW Output Voltage Swing HIGH CONDITIONS Guaranteed by PSRR (Note 8) -IN = V+, +IN = Half Supply (Note 8) -IN = 0V, +IN = Half Supply VS = 3V, 0V, Below V+ VS = 5V, 0V, Below V+ Short to GND (Note 9) Short to V+ (Note 9)

MIN
TYP
MAX 2.7 170 70 200 225
UNITS V A mV mV mV mA mA
ISC
Output Short-Circuit Current
2 8
15V ELECTRICAL CHARACTERISTICS
VS = 15V, RL = 10k, VCM = VREF = 0V, G = 1, 10, TA = 25C, unless otherwise noted. (Note 6)
SYMBOL G G PARAMETER Gain Gain Error CONDITIONS Pins 5 and 8 = Open Pins 5 and 8 = VREF VOUT = 10V LT1990, G = 1 LT1990A, G = 1 G = 10 VOUT = 10V G=1 G = 10 Guaranteed by CMRR VCM = -250V to 250V LT1990 LT1990A G = 1, 10 fO = 0.1Hz to 10Hz fO = 1kHz Differential Common Mode VS = 1.35V to 18V Guaranteed by PSRR 14.5 Short to V- Short to V+ Bandwidth Slew Rate Settling Time to 0.01% AVREF Reference Gain to Output G=1 G = 10 G = 1, VOUT = 10V 10V Step, G = 1 0.3 6 15 82 -250 60 70 68 75 0.9 22 1 2 0.5 100 1.2 140 14.79 9 22 105 7 0.55 60 1 0.0007 1.35 180 5.2 MIN TYP 1 10 0.4 0.07 0.2 0.6 0.28 0.8 % % % % % V dB dB mV VP-P V/Hz M M dB V A V mA mA kHz kHz V/s s MAX UNITS
GNL
Gain Nonlinearity
0.0008 0.002 0.005 0.02 250
VCM CMRR
Input Voltage Range Common Mode Rejection Ratio, RTI
VOS en RIN PSRR IS VOUT ISC BW SR
Offset Voltage, RTI Input Noise Voltage, RTI Noise Voltage Density, RTI Input Resistance Power Supply Rejection Ratio, RTI Minimum Supply Voltage Supply Current Output Voltage Swing Output Short-Circuit Current
1990f
5
LT1990
15V ELECTRICAL CHARACTERISTICS
The denotes the specifications which apply over the temperature range of 0C TA 70C. VS = 15V, RL = 10k, VCM = VREF = 0V, G = 1, 10, unless otherwise noted. (Notes 4, 6)
SYMBOL G PARAMETER Gain Error CONDITIONS VOUT = 10V LT1990, G = 1 LT1990A, G = 1 G = 10 VOUT = 10V G=1 G = 10 G = 1 (Note 10) G = 10 (Note 10) Guaranteed by CMRR VCM = -250V to 250V LT1990 LT1990A G = 1, 10 (Note 10) (Note 11) VS = 1.35V to 16V Guaranteed by PSRR

MIN
TYP
MAX 0.65 0.33 0.9 0.0025 0.025
UNITS % % % % % ppm/C ppm/C V dB dB
GNL
Gain Nonlinearity
G/T VCM CMRR
Gain vs Temperature Input Voltage Range Common Mode Rejection Ratio, RTI
2 7 -250 59 68
10 20 250
VOS VOS/T VOSH PSRR IS VOUT ISC SR
Input Offset Voltage, RTI Input Offset Voltage Drift, RTI Input Offset Voltage Hysteresis, RTI Power Supply Rejection Ratio, RTI Minimum Supply Voltage Supply Current Output Voltage Swing Output Short-Circuit Current Slew Rate
6.2 5 250 80 1.35 230 14.4 5 13 0.25 22
mV V/C V dB V A V mA mA V/s
Short to V- Short to V+ G = 1, VOUT = 10V

1990f
6
LT1990
15V ELECTRICAL CHARACTERISTICS
The denotes the specifications which apply over the temperature range of -40C TA 85C. VS = 15V, RL = 10k, VCM = VREF = 0V, G = 1, 10, unless otherwise noted. (Notes 4, 6)
SYMBOL G PARAMETER Gain Error CONDITIONS VOUT = 10V LT1990, G = 1 LT1990A, G = 1 G = 10 VOUT = 10V G=1 G = 10 G = 1 (Note 10) G = 10 (Note 10) Guaranteed by CMRR VCM = -250V to 250V LT1990 LT1990A G = 1, 10 (Note 10) (Note 11) VS = 1.35V to 18V Guaranteed by PSRR

MIN
TYP
MAX 0.67 0.35 0.9 0.003 0.03
UNITS % % % % % ppm/C ppm/C V dB dB
GNL
Gain Nonlinearity
G/T VCM CMRR
Gain vs Temperature Input Voltage Range Common Mode Rejection Ratio, RTI
2 7 -250 58 67
10 20 250
VOS VOS/T VOSH PSRR IS VOUT ISC SR
Input Offset Voltage, RTI Input Offset Voltage Drift, RTI Input Offset Voltage Hysteresis, RTI Power Supply Rejection Ratio, RTI Minimum Supply Voltage Supply Current Output Voltage Swing Output Short-Circuit Current Slew Rate
6.7 5 250 78 1.35 280 14.3 3 10 0.2 22
mV V/C V dB V A V mA mA V/s
Short to V- Short to V+ G = 1, VOUT = 10V

Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: ESD (Electrostatic Discharge) sensitive device. Extensive use of ESD protection devices are used internal to the LT1990, however, high electrostatic discharge can damage or degrade the device. Use proper ESD handling precautions. Note 3: A heat sink may be required to keep the junction temperature below absolute maximum. Note 4: The LT1990C/LT1990I are guaranteed functional over the operating temperature range of - 40C to 85C. Note 5: The LT1990C is guaranteed to meet the specified performance from 0C to70C and is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LT1990I is guaranteed to meet specified performance from -40C to 85C.
Note 6: G = 10 limits are guaranteed by correlation to G = 1 tests and gain error tests at G = 10. Note 7: Limits are guaranteed by correlation to -5V to 80V CMRR tests. Note 8: VS = 3V limits are guaranteed by correlation to VS = 5V and VS = 15V tests. Note 9: VS = 5V limits are guaranteed by correlation to VS = 3V and VS = 15V tests. Note 10: This parameter is not 100% tested. Note 11: Hysteresis in offset voltage is created by package stress that differs depending on whether the IC was previously at a higher or lower temperature. Offset voltage hysteresis is always measured at 25C, but the IC is cycled to 85C I-grade (or 70C C-grade) or -40C I-grade (0C C-grade) before successive measurement.
1990f
7
LT1990 TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
220 200
SUPPLY CURRENT (A)
VREF = VOUT = 1.25V V - = 0V TA = 125C
SUPPLY CURRENT (A)
OUTPUT VOLTAGE SWING WITH RESPECT TO SUPPLY (V)
180 160 140 120 100 80 60 40 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V)
Output Voltage vs Input Voltage, G = 1
V + -0.01 VS = 2.5V G=1 -0.1 NO LOAD -1 TA = -55C TA = 125C TA = 25C
OUTPUT VOLTAGE WITH RESPECT TO SUPPLY (V)
OUTPUT VOLTAGE WITH RESPECT TO SUPPLY (V)
TA = 25C -1
OUTPUT SWING WITH RESPECT TO SUPPLY (V)
+1 +0.1 TA = 25C TA = -55C 0 TA = 125C 4.0
V - +0.01
0.5 1.0 1.5 2.0 2.5 3.0 3.5 DIFFERENTIAL INPUT VOLTAGE (V)
Output Short-Circuit Current vs Supply Voltage
25
OUTPUT SHORT-CIRCUIT CURRENT (mA)
20 15 10 5 0 -5 -10 -15 -20 -25 -30 0
SOURCE TA = -55C TA = 25C TA = 125C SINK TA = 125C TA = -55C TA = 25C 2 4 8 10 12 6 SUPPLY VOLTAGE (V) 14 16
MAXIMUM INPUT VOLTAGE (V)
VREF = 4V 150 100 50 0 -50 VREF = 1.25V VREF = 2.5V VREF = 4V 3 7 9 11 13 5 POSITIVE SUPPLY VOLTAGE (V) 15
1990 G08
VREF = 1.25V VREF = 2.5V
MAXIMUM INPUT VOLTAGE (V)
8
UW
35
Supply Current vs Temperature
150 140 - 0.1 -1 130 120 110 100 90 80 70 40 60 -50 -25 0 25 50 75 TEMPERATURE (C) 100 125 VS = 5V, 0V V + - 0.01
Output Voltage Swing vs Load Current
TA = -55C SOURCING (+IN = 2.5V) VS = 2.5V -IN = 0V G=1
TA = 85C TA = 25C TA = -40C TA = -55C
TA = 125C TA = 25C TA = 25C
+1 +0.1 SINKING (+IN = -2.5V)
TA = 125C TA = -55C
V - +0.01 0.001
0.01 0.1 1 10 OUTPUT CURRENT (mA)
100
1990 G03
1990 G01
1990 G02
Output Voltage vs Input Voltage, G = 10
V + -0.01 VS = 2.5V G = 10 -0.1 NO LOAD TA = -55C TA = 125C V + -0.01
Output Voltage Swing vs Supply Voltage
G = 1, V+IN = V+ -0.1 G = 10, V = V+/10 +IN V-IN = 0V VREF = 0V NO LOAD TA = 25C +0.1 G = 10, V+IN = V -/10 G = 1, V+IN = V -
G=1 G = 10 OUTPUT FULLY SATURATED OUTPUT FULLY SATURATED G = 10 G = 1
+1 TA = 25C +0.1 TA = 125C
V - +0.01 0
TA = -55C 0.2 0.4 0.6 0.8 DIFFERENTIAL INPUT VOLTAGE (V) 1.0
V - +0.01 0
2
4 6 8 10 12 SUPPLY VOLTAGE (V)
14
16
1990 G04
1990 G05
1990 G06
Input Voltage Range vs Single Supply Voltage
250 200 V - = 0V TA = -40C TO 85C 300 200 100 0 -100 -200 -300
Input Voltage Range vs Split Supply Voltage
VREF = 0V TA = -40C TO 85C
-100
1
3
9 7 11 5 SUPPLY VOLTAGE (V)
13
15
1990 G07
1990 G09
1990f
LT1990 TYPICAL PERFOR A CE CHARACTERISTICS
Common Mode Rejection Ratio vs Frequency
100
COMMON MODE REJECTION RATIO (dB)
90 80 70
GAIN (dB)
60 50 40 30 20 10 0 100 10k 1k FREQUENCY (Hz) 100k 200k
1990 G10
-3dB Bandwidth vs Supply Voltage, G = 1
120 115 110
FREQUENCY (kHz)
TA = 25C TA = -55C
FREQUENCY (kHz)
100 95 90 85 80 75 70 0 2
TA = 125C TA = 25C
6
TA = 25C
TA = 125C
SLEW RATE (V/s)
105
6 8 4 10 12 SUPPLY VOLTAGE (V)
Slew Rate vs Supply Voltage, G = 10
0.5 TA = 25C RL = 10k 1.0
0.4
SLEW RATE (V/s) SLEW RATE (V/s)
SLEW RATE (V/s)
0.3
-SR +SR
0.2
0.1
0 0 2 8 6 10 12 4 SUPPLY VOLTAGE (V) 14 16
UW
14
1990 G13 1990 G16
Gain vs Frequency
50 VS = 5V, 0V 40 TA = 25C 30 20 10 0 -10 -20 -30 -40 -50 100 1k 10k 100k FREQUENCY (Hz) 1M
1990 G12
VS = 5V, 0V TA = 25C G = 1 OR 10 REFERRED TO INPUT
G = 10
G=1
-3dB Bandwidth vs Supply Voltage, G = 10
8 TA = 25C TA = -55C 7 0.8 1.0
Slew Rate vs Supply Voltage, G=1
TA = 25C RL = 10k
-SR 0.6 +SR 0.4
5
4
0.2
3 16 0 2 6 8 4 10 12 SUPPLY VOLTAGE (V) 14 16
0 0 2 8 6 10 12 4 SUPPLY VOLTAGE (V) 14 16
1990 G14
1990 G15
Slew Rate vs Temperature G=1
0.6 VS = 15V RL = 10k 0.8 -SR 0.6 +SR 0.4 0.5 0.4 0.3 0.2 0.1
Slew Rate vs Temperature G = 10
VS = 15V RL = 10k
-SR +SR
0.2
0 -50 -25
50 25 75 0 TEMPERATURE (C)
100
125
0 -50 -25
50 25 75 0 TEMPERATURE (C)
100
125
1990 G17
1990 G18
1990f
9
LT1990 TYPICAL PERFOR A CE CHARACTERISTICS
Output Impedance vs Frequency
5k
POWER SUPPLY REJECTION RATIO (dB)
CHANGE IN OFFSET VOLTAGE (V)
1k
OUTPUT IMPEDANCE ()
G = 10
100
G=1
10 VS = 5V, 0V TA = 25C 10k 1k FREQUENCY (Hz) 100k 200k
1990 G19
1 100
Settling Time vs Output Step, G=1
60 VS = 15V RL = 10k
SETTLING TIME (s)
50
SETTLING TIME (s)
280 260 240 220 200 180 160 6 8 10 140 -10 -8 -6 -4 -2 0 2 4 OUTPUT STEP (V) 6 8 10 0.1% OF STEP 0.01% OF STEP 0.01% OF STEP
40
0.01% OF STEP 0.01% OF STEP
VOLTAGE NOISE DENSITY (nV/Hz)
30 0.1% OF STEP 20 -10 -8 -6 -4 -2 0 2 4 OUTPUT STEP (V)
0.1 to 10Hz Noise Voltage
VS = 1.5V TO 15V TA = 25C G=1
NOISE VOLTAGE (10V/DIV)
NOISE VOLTAGE (10V/DIV)
OVERSHOOT (%)
REF
0
1
2
3
456 TIME (S)
7
10
UW
0.1% OF STEP
1990 G22
Power Supply Rejection Ratio vs Frequency
70 60 50 40 30 20 10 0 -10 -20 -30 -40 10 -60 100 1k 10k FREQUENCY (Hz) 100k 200k
1990 G20
Warm-Up Drift vs Time
60 40 20 0 -20 -40 VS = 15V TA = 25C REFERRED TO INPUT
G=1
VS = 5V, 0V TA = 25C
G = 10
0
10 20 30 40 TIME AFTER POWER-UP (S)
50
1990 G21
Settling Time vs Output Step, G = 10
320 300 VS = 15V RL = 10k 10000
Voltage Noise Density vs Frequency
VS = 1.5V TO 15V TA = 25C
1000
0.1% OF STEP
100 1 10 100 1000 FREQUENCY (Hz) 10000
1990 G24
1990 G23
0.01 to 1Hz Noise Voltage
VS = 1.5V TO 15V TA = 25C G=1 30
Overshoot vs Capacitive Load
VOUT = 50mV GAIN = 1 RL = 10k
25
20
REF
15 VS = 3V, 0V 10 VS = 15V 5
8
9
10
0
10 20 30 40 50 60 70 80 90 100 TIME (S)
1990 G26
10
100 1000 CAPACITIVE LOAD (pF)
10000
1990 G27
1990 G25
1990f
LT1990 TYPICAL PERFOR A CE CHARACTERISTICS
Small Signal Transient Response Small Signal Transient Response Large Signal Transient Response
50mV/DIV
50mV/DIV
1.5V
GND
5V/DIV
1990 G29
VS = 3V, 0V G = 1, -1 RL = 10k VREF = 1.5V
50s/DIV
BLOCK DIAGRA
PI FU CTIO S
REF (Pin 1): Reference Input. Sets the output level when the difference between the inputs is zero. -IN (Pin 2): Inverting Input. Connects a 1M resistor to the op amp's inverting input. Designed to permit high voltage operation. +IN (Pin 3): Noninverting Input. Connects a 1M resistor to the op amp's noninverting input. Designed to permit high voltage operation. V- (Pin 4): Negative Power Supply. Can be either ground (in single supply applications) or a negative voltage (in split supply applications). GAIN2 (Pin 5): Gain = 10 Select Input. Configures the amplifier for a gain of 10 when connected to the GAIN1 pin. The gain is equal to one when both GAIN2 and GAIN1 are open. See Applications section for additional functions. OUT (Pin 6): Output. VOUT = G * (V+IN - V-IN) + VREF, in the basic configuration. V+ (Pin 7): Positive Power Supply. Can range from 2.7V to 36V above the V- voltage. GAIN1 (Pin 8): Gain = 10 Select Input. Configures the amplifier for a gain of 10 when connected to the GAIN2 pin. The gain is equal to one when both GAIN1 and GAIN2 are open. See Applications section for additional functions.
1990f
UW
1990 G28
GND
VS = 15V G = 1, -1 RL = 10k VREF = GND
50s/DIV
VS = 15V G = 1, -1 RL = 10k VREF = GND
50s/DIV
1990 G30
W
R5 900k V+ 7 R1 1M -IN 2 R2 1M +IN 3 V- 4 R3 40k R4 40k R8 900k R9 100k R10 10k 5 GAIN2 R7 10k 8 GAIN1 R6 100k 6 OUT
- +
1 REF
1990 SS
U
U
U
11
LT1990
APPLICATIO S I FOR ATIO
Primary Features The LT1990 is a complete gain-block solution for high input common mode voltage applications, incorporating a low power precision operational amplifier providing railto-rail output swing along with on-chip precision thin-film resistors for high accuracy. The Block Diagram shows the internal architecture of the part. The on-chip resistors form a modified difference amplifier including a reference port for introducing offset or other additive waveforms. With pin-strapping alone either unity gain or gain of 10 is produced with high precision. The resistor network is designed to produce internal common-mode voltage division of 27 so that a very large input range is available compared to the power supply voltage(s) used by the LT1990 itself. The LT1990 is ideally suited to situations where relatively small signals need to be extracted from high voltage circuits, as is the case in many current monitoring instrumentation applications for example. With the ability to accept a range of input voltages well outside the limits of the local power rails and its greater than 1M input impedances, development of precision low power over-the-top and under-the-bottom instrumentation designs is greatly simplified with the LT1990 single chip solution over conventional discrete implementations. Classic Difference Amplifier Used in the basic difference amplifier topology where the gain G is pin-strap configurable to be unity or ten, the following relationship is realized: VO = G * (V+IN - V-IN) + VREF To operate in unity gain, the GAIN1 and GAIN2 pins are left disconnected. For G = 10 operation, the GAIN1 and GAIN2 pins are simply connected together or tied to a common potential such as ground or V -. The input common mode range capability is up to 250V, governed by the following relationships: For G = 1 and G = 10 where GAIN1 and GAIN2 are only tied together (not grounded,etc): VCM+ 27 * V+ - 26 * VREF - 23 VCM- 27 * V - - 26 * VREF + 27
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For G = 10 where GAIN1 and GAIN2 are tied to a common potential VGAIN: VCM+ 27 * V+ - 26 * VREF - 23 - VGAIN VCM- 27 * V- - 26 * VREF + 27 - VGAIN For split supplies over about 11V, the full 250V common mode range is normally available (with VREF a small fraction of the supply). With lower supply voltages, an appropriate selection of VREF can tailor the input common mode range to a specific requirement. As an example, the following low supply voltage scenarios are readily implemented with the LT1990:
Supply +3V +5V +5V VREF 1.25V 1.25V 4.00V VCM Range -5V to 25V (e.g. 12V automotive environment) -5V to 80V (e.g. 42V automotive environment) -77V to 8V (e.g. telecom environment; use downward signaling)
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Configuring Other Gains An intermediate gain G ranging between 1 and 10 may be produced by placing an adjustable resistance between the GAIN1 and GAIN2 pins according to the following nominal relationship: RGAIN (180k/(G - 1)) - 20k While the expression is exact, the value is approximate because the absolute resistance of the internal network could vary on a unit-to-unit basis by as much as 30% from the nominal figures and the external gain resistance is required to accommodate that deviation. Once adjusted, however, the gain stability is excellent by virtue of the -30ppm/C typical temperature coefficient offered by the on-chip thin-film resistor process. Preserving and Enhancing Common Mode Rejection The basic difference amplifier topology of the LT1990 requires that source impedances seen by the input pins +IN and -IN, should be matched to within a few tens of ohms to avoid increasing common mode induced errors beyond the basic production limits of the part. Known source imbalances beyond that level should be compensated for by the addition of series resistance to the lower1990f
LT1990
APPLICATIO S I FOR ATIO
impedance source. Also the source impedance of a signal connected to the REF pin must be on the order of a few ohms or less to preserve the high accuracy of the LT1990. While the LT1990 comes from the factory with an excellent CMRR, some precision applications with a large applied common mode voltage may require a method to trim out residual common mode error. This is easily accomplished by adding series resistance to each input, +IN and -IN, such that an adjustable resistance difference of 1k is provided. This is most easily realized by adding a fixed 1k in series with one of the inputs, and a 2k trimmer in series with the other as shown in Figure 1. The trim range of this configuration is 0.1% for the internal gain resistor matching, so a much more finely resolved correction is available using the LT1990 than is realizable with ordinary discrete solutions. In applications where the input common mode voltage is relatively constant and large (perhaps at or beyond the supply range), this same configuration can be treated as an offset adjustment.
1k
-
LT1990
2k
+
Figure 1. Optional CMRR Trim
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Dual Differential-Input Arithmetic Block The internal resistor network topology of the LT1990 allows the GAIN1 and GAIN2 pins to be used as another differential input in addition to the normal +IN and -IN port. This can be a very useful function for implementing servo-loop differential error amplifiers, for example. In this mode of operation, the output is governed by the following relationship: VO = 10 * (V+IN - V-IN + VGAIN2 - VGAIN1) + VREF Unlike the main inputs, the GAIN1 and GAIN2 pins are clamped by substrate diodes and ESD structures, thus the operating voltage range of these pins is limited to V- - 0.2V to V- + 36V. If the GAIN inputs are brought beyond the operating input range, care must be taken to limit the input currents to less than 10mA to prevent damage to the device. Also, since the gain setting resistors associated with the GAIN1 and GAIN2 inputs are in the 10k area, low source impedances are particularly important to preserve the precision of the LT1990. This dual differential input mode of operation is used in the circuit as shown in Figure 2. This circuit is a high efficiency H-bridge driver that is PWM modulated to provide a controlled current to an electromagnet coil. Since the common mode voltage of the current sense resistor RS varies with operating current and the coil properties, a differential feedback is required. In this application, it was desirable to allow the control input to utilize the wide common mode range port (+IN and -IN) so that constraints on input referencing are eliminated. The GAIN1 and GAIN2 pins always operate within the supply range and both ports operate with a gain of 10 to develop the loop error. The LTC1923 provides the loop integrator and PWM functions of the servo.
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LT1990
APPLICATIO S I FOR ATIO
VIN+ 100k 3 20k 2 100k VIN- ICOIL = (VIN+ - VIN)/(10 * RS) (i.e. 1A FOR 1V) VDD 7 5 LT1990 REF 4 G2 G1 6 10nF
82k RSLEW VDD 100k 100k 10nF CNTRL EAOUT FB LTC1923 1F AGND SS ILIM VSET 10k FAULT VTHRM 10k H/C VTEC PGND NDRVA PDRVA CS + CS - ITEC TEC + TEC - PDRVB NDRVB VDD 1F SDSYNC CT VREF VREF
+ -
1
8
C1, C2, C3: TAIYO YUDEN JMK325BJ226MM-T (X7R) L1, L2: SUMIDA CDRH6D2B-220NC *MNA, MPA: SILICONIX Si9801 **MNB, MPB: SILICONIX Si9801
Figure 2. PWM-Based 1A Electromagnet Current Controller
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10k PLLLPF RT 330pF 1F VDD 10F MPA* L1 10H C1 MNB** 22F C3 22F MPB** L2 10H C2 22F MNA* 0.1 RS 0.1 ICOIL ELECTROMAGNET COIL
1990 F02
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1990f
LT1990
PACKAGE DESCRIPTIO U
S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 - .197 (4.801 - 5.004) NOTE 3 8 7 6 5 .045 .005 .050 BSC .160 .005 .228 - .244 (5.791 - 6.197) .150 - .157 (3.810 - 3.988) NOTE 3 1 2 3 4 .053 - .069 (1.346 - 1.752) 0- 8 TYP .004 - .010 (0.101 - 0.254) .014 - .019 (0.355 - 0.483) TYP .050 (1.270) BSC
SO8 0303
.245 MIN
.030 .005 TYP RECOMMENDED SOLDER PAD LAYOUT .010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254)
.016 - .050 (0.406 - 1.270) NOTE: 1. DIMENSIONS IN
INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
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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.
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LT1990
TYPICAL APPLICATIO
+
LOAD IL 48V
Telecom Supply Current Monitor
5V
-
RS
3
+ -
1
LT1990 2 4 G1
-77V VCM 8V VOUT = VREF - (10 * IL * RS) 4 IN
REF 5 OUT LT6650 1 GND FB 2
Bidirectional Controlled Current Source
+V VCTL 3 7 LT1990 2 6 RSENSE ILOAD
+ -
1
4 -V
REF
ILOAD = VCTL/RSENSE 5mA EXAMPLE: FOR RSENSE =100, OUTPUT IS 1mA PER 100mV INPUT
1990 AI03
RELATED PARTS
PART NUMBER LT1787 LT1789 LTC1921 LT1991 LT1995 LT6910 DESCRIPTION Precision High Side Current Sense Amplifier Micropower Instrumentation Amplifier Dual -48V Supply and Fuse Monitor High Accuracy Difference Amplifier 30MHz, 1000V/s Gain Selectable Amplifier Single Supply Programmable Gain Amplifier COMMENTS On-Chip Precision Resistor Array Micropower, Precision, G = 1 to 1000 Withstands 200V Transients Micropower, Precision, Pin Selectable G = -13 to 14 Pin Selectable G = -7 to 8 Digitally Controlled, SOT-23, G = 0 to 100
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Selectable Gain Amplifier
+V VIN+
7 G2 56 8
3
+ -
1
7 LT1990
G2
56 8
VOUT
VOUT
VIN-
2
4 G1 -V
VREF
VREF = 4V 174k 1nF
REF
2N7002
GAIN_SEL (HI = 10X, LO = 1X)
2N7002
20k
1990 AI01
1990 AI02
1F
Boosted Bidirectional Controlled Current Source
+V
1k CZT751 VCTL 3
+ -
1
7 LT1990 6
2
+
10F RSENSE ILOAD
4
REF 1k
CZT651
-V ILOAD = VCTL/RSENSE 100mA EXAMPLE: FOR RSENSE =10, OUTPUT IS 1mA PER 10mV INPUT
1990 AI04
1990f LT/TP 0704 1K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2004

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