LT1787/LT1787HV
Precision, High Side
Current Sense Amplifiers
FEATURES
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Input Offset Voltage: 75
µ
V (Max)
60V Supply Operation (LT1787HV)
12-Bit Dynamic Range
Operating Current: 60µA
User-Selectable External Sense Resistor
Bidirectional High Side Current Sensing
Unidirectional or Bidirectional Output
Input Noise Filtering
Available in 8-Lead SO and MSOP Packages
APPLICATIO S
s
s
s
s
s
s
Battery Monitoring
Power Monitoring
Portable Phones
Cellular Phones
Portable Test/Measurement Systems
Battery-Operated Systems
The LT
®
1787 is a complete micropower precision high
side current sense amplifier. The LT1787 monitors bidi-
rectional currents via the voltage across an external sense
resistor. A current or voltage output depicts the direction
and magnitude of the sense current. The LT1787 delivers
greater than a 12-bit dynamic range with ultralow 40µV
input offset voltage compared to a typical 250mV full-
scale input voltage. A fixed gain of 8 is set by onboard
precision resistors. Input signal filtering is easily imple-
mented with a capacitor between the FIL
–
and FIL
+
pins.
The LT1787HV operates from 2.5V to 60V total supply
voltage and the LT1787 operates from 2.5V to 36V total
supply voltage. Both versions have a PSRR in excess of
120dB. The LT1787/LT1787HV draw only 60µA and are
available in 8-lead SO and MSOP packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
12-Bit Dynamic Resolution Unidirectional Output into LTC
®
1286 ADC
TO
LOAD
I = 100A
1
FIL
–
LT1787HV
R
SENSE
0.0016Ω
FIL
+
8
2.5V TO 60V
INPUT OFFSET VOLTAGE (µV)
50
40
30
20
10
0
–10
–20
–30
–40
–50
0
10
30
40
50
20
TOTAL SUPPLY VOLTAGE (V)
60
–
2 V
S
V
S+
7
3
4
DNC
V
EE
V
BIAS
6
R
OUT
20k
V
OUT
C2
0.1µF
5
R1
15k
C1
1µF
V
REF
V
CC
CS
+IN
LTC1286 CLK
–IN
D
GND
OUT
5V
TO
µP
V
OUT
= V
BIAS
+ (8 • I
LOAD
• R
SENSE
)
LT1634-1.25
1787 TA01
U
Input Offset Voltage vs Supply Voltage
1787 TA01b
U
U
1
LT1787/LT1787HV
ABSOLUTE
MAXIMUM
RATINGS
Differential Sense Voltage ......................................
±10V
Total Supply Voltage (LT1787) ................................ 40V
Total Supply Voltage (LT1787HV) ........................... 65V
Output Voltage ..................... (V
EE
– 0.3V) to (V
EE
+ 35V)
Output Bias Voltage ............. (V
EE
– 0.3V) to (V
EE
+ 35V)
PACKAGE/ORDER INFORMATION
TOP VIEW
FIL
–
1
V
S–
2
DNC* 3
V
EE
4
8
7
6
5
FIL
+
V
S+
V
BIAS
V
OUT
MS8 PACKAGE
8-LEAD PLASTIC MSOP
* DO NOT CONNECT
T
JMAX
= 150°C,
θ
JA
= 250°C/ W
ORDER PART NUMBER
LT1787CMS8
LT1787IMS8
LT1787HVCMS8
LT1787HVIMS8
MS8 PART MARKING
LTGM
LTGN
LTKJ
LTKK
(Note 4)
The
q
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
Total supply = (V
S–
– V
EE
) = 2.5V to 36V (LT1787), 2.5V to 60V (LT1787HV) unless otherwise specified.
SYMBOL
V
S –
, V
S +
V
SENSE
V
OS
PARAMETER
CONDITIONS
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
Sense Amplifier Supply Voltage Single Supply Operation (LT1787)
Single Supply Operation (LT1787HV)
Input Sense Voltage Full Scale
Input Offset Voltage (S8)
V
SENSE
= V
S+
– V
S–
, V
S
= 10V, V
BIAS
= 5V, A
V
= 8
±10%
I
OUT
= 0, V
S
Supply = 5V
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
I
OUT
= 0 (LT1787)
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
I
OUT
= 0 (LT1787HV)
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
Input Offset Voltage (MS8)
I
OUT
= 0, V
S
Supply = 5V
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
I
OUT
= 0 (LT1787)
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
I
OUT
= 0 (LT1787HV)
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
2
U
U
W
W W
U
W
(Notes 1, 2)
Operating Temperature Range ................ – 40°C to 85°C
Specified Temperature Range (Note 3) ... – 40°C to 85°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
FIL
–
1
V
S–
2
DNC* 3
V
EE
4
8
7
6
5
FIL
+
V
S+
V
BIAS
V
OUT
ORDER PART NUMBER
LT1787CS8
LT1787IS8
LT1787HVCS8
LT1787HVIS8
S8 PART MARKING
1787
1787I
1787HV
787HVI
S8 PACKAGE
8-LEAD PLASTIC SO
* DO NOT CONNECT
T
JMAX
= 150°C,
θ
JA
= 190°C/ W
Consult factory for Military grade parts.
MIN
2.5
2.5
500
– 75
– 135
– 200
– 100
– 160
– 225
– 100
– 160
– 225
– 125
– 230
– 250
– 150
– 250
– 280
– 150
– 250
– 280
TYP
MAX
36
60
UNITS
V
V
mV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
µV
±40
75
135
200
100
160
225
100
160
225
±40
125
230
250
150
250
280
150
250
280
LT1787/LT1787HV
ELECTRICAL CHARACTERISTICS
SYMBOL
V
OS
TC
I
OUT(O)
V
OUT(O)
PARAMETER
Temperature Coefficient of V
OS
No-Load Output Current Error
No-Load Output Voltage Error
(S8)
No-Load Output Voltage Error
(MS8)
g
m
A
V
V
S
PSRR
Tranconductance, I
OUT
/ V
SENSE
Gain, V
OUT
/ V
SENSE
Output Voltage Gain Error
V
S
Supply Rejection Ratio
CONDITIONS
(Note 4)
The
q
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
Total supply = (V
S –
– V
EE
) = 2.5V to 36V (LT1787), 2.5V to 60V (LT1787HV) unless otherwise specified.
MIN
TYP
0.5
4
q
q
q
q
MAX
2
600
1080
1600
1000
1840
2000
UNITS
µV/°C
nA
µV
µV
µV
µV
µV
µV
µA/V
V
S
Supply = 5V (Note 5)
V
SENSE
= 0V
V
SENSE
= 0V, V
S
Supply = 5V
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
V
SENSE
= 0V, V
S
Supply = 5V
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
±V
SENSE
= 10mV, 50mV, 100mV, 150mV, 250mV,
V
S
Supply = Total Supply + |V
SENSE
|
±V
SENSE
= 100mV, V
S
Supply = 5V
V
SENSE
= 0V, V
S
Supply = 2.5V to 36V (LT1787)
V
SENSE
= 0V, V
S
Supply = 2.5V to 60V (LT1787HV)
q
q
q
q
q
q
–600
– 1080
– 1600
– 1000
– 1840
– 2000
400
7.6
–5
120
120
100
100
100
100
8
2
135
135
130
130
130
130
10
50
60
±50
V
BIAS
±1.024
8.4
5
V/V
%
dB
dB
dB
dB
dB
dB
V
EE
PSRR Negative Supply Rejection Ratio V
SENSE
= 0V, V
S
Supply = 15V, V
BIAS
= 0V,
V
EE
= – 1V to – 15V (LT1787)
V
SENSE
= 0V, V
S
Supply = 40V, V
BIAS
= 0V,
V
EE
= – 1V to – 15V (LT1787HV)
∆V
OS
∆V
BIAS
I
S+(O)
I
S–(O)
I
EE(O)
I
OUT
V
OUT
V
OMIN
Change in Input Offset Voltage
with Change in V
BIAS
Voltage
Positive Input Sense Current
Negative Input Sense Current
Negative Supply Current
Output Current
Output Voltage
Ripple Rejection
Minimum Output Voltage
Unipolar Output
Saturation Voltage
V
SENSE
= 0V, V
S
Supply = 36V, V
BIAS
= 0.5V to 25V (LT1787)
q
V
SENSE
= 0V, V
S
Supply = 60V, V
BIAS
= 0.5V to 25V (LT1787HV)
q
V
SENSE
= 0V
V
SENSE
= 0V
V
SENSE
= 0V
V
SENSE
=
±128mV
V
SENSE
=
±128mV,
V
S+
≥
3.3V
V
S+
= V
S–
= 20V,
∆V
S
Supply = 1V, f = 1kHz
V
SENSE
= 0V, V
BIAS
= 0V
V
SENSE
= V
S+
– V
S–
= –128mV, V
BIAS
= 0V
V
SENSE
= 2mV, V
BIAS
= 0V
V
SENSE
= 4mV, V
BIAS
= 0V
V
SENSE
= 5mV, V
BIAS
= 0V
V
SENSE
= 6mV, V
BIAS
= 0V
Pin 1 to Pin 2, Pin 7 to Pin 8
Pin 5 to Pin 6
q
q
q
q
q
q
q
q
q
20
100
120
µA
µA
µA
µA
V
dB
80
88
30
10
32
38
43
49
V
S +
– 0.75
1.25
20
45
50
55
60
65
mV
mV
mV
mV
mV
mV
V
kΩ
kΩ
V
OMAX
R
OUT
Maximum Output Voltage
Output Resistor
R
G1A,
R
G2A
Input Gain-Setting Resistor
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
ESD (Electrostatic Discharge) sensitive devices. Extensive use of
ESD protection devices are used internal to the LT1787/LT1787HV,
however, high electrostatic discharge can damage or degrade the device.
Use proper ESD handling precautions.
Note 3:
The LT1787C/LT1787HVC are guaranteed to meet specified
performance from 0°C to 70° and are designed, characterized and
expected to meet these extended temperature limits, but are not tested at
– 40°C and 85°C. The LT1787I/LT1787HVI are guaranteed to meet the
extended temperature limits.
Note 4:
Testing done at V
BIAS
= 1.25V, V
EE
= 0V unless otherwise
specified.
Note 5:
This parameter is not 100% tested.
3
LT1787/LT1787HV
TYPICAL PERFORMANCE CHARACTERISTICS
Input Offset Voltage vs
Supply Voltage
50
40
INPUT OFFSET VOLTAGE (µV)
30
20
10
0
–10
–20
–30
–40
–50
0
10
30
40
50
20
TOTAL SUPPLY VOLTAGE (V)
60
1787 G01
V
S+
= V
S–
V
BIAS
= 0V
V
EE
= –1.25V
OUTPUT VOLTAGE (µV)
OUTPUT CURRENT (nA)
T
A
= 85°C
T
A
= 25°C
T
A
= –40°C
Input Offset Voltage vs
Negative Supply Voltage
30
20
10
0
–10
T
A
= –40°C
–20
–30
V
S+
= V
S–
= 2.5V
V
BIAS
= 1V
T
A
= 85°C
INPUT OFFSET VOLTAGE (µV)
INPUT OFFSET VOLTAGE (µV)
20
10
0
–10
–20
–30
–40
OUTPUT VOLTAGE (V)
T
A
= 25°C
0
–5
–10
–15
–20
–25
NEGATIVE SUPPLY VOLTAGE (V)
Output Voltage vs Sense Voltage
(Unidirectional Mode)
1.4
1.2
OUPUT VOLTAGE (V)
V
S
= 2.5V TO 60V
T
A
= –40°C TO 85°C
V
BIAS
= V
EE
1.0
GAIN (V/V)
0.8
0.6
0.4
0.2
0
0
120
+
– V
–
) (mV)
SENSE VOLTAGE (V
S
S
30
60
90
150
8.165
8.155
8.145
V
S+
< V
S–
GAIN (dB)
4
U W
1787 G04
No Load Output Voltage
vs Supply Voltage
400
300
200
100
0
–100
–200
T
A
= –40°C
–300
–400
0
50
20
30
40
10
TOTAL SUPPLY VOLTAGE (V)
60
1787 G02
No Load Output Current vs
Supply Voltage
10
8
T
A
= –40°C
T
A
= 25°C
V
S+
= V
S–
V
BIAS
= 0V
V
EE
= –1.25V
T
A
= 85°C
6
4
2
0
–2
–4
–6
–8
–10
0
10
30
40
50
20
TOTAL SUPPLY VOLTAGE (V)
60
1787 G03
T
A
= 25°C
T
A
= 85°C
V
BIAS
= 1V
V
EE
= 0V
V
S+
= V
S–
Input Offset Voltage vs
Temperature
50
40
30
V
S+
= V
S–
V
BIAS
= 0V
V
EE
= –1.25V
2.5
2.0
1.5
1.0
0.5
V
BIAS
–0.5
–1.0
–1.5
–2.0
–2.5
–20
0
20
40
TEMPERATURE (°C)
60
80
85
1787 G05
Output Voltage vs Sense Voltage
(Bidirectional Mode)
V
S
= 5.5V TO 60V
V
BIAS
= 2.5V
V
EE
= 0V
–30
–50
–40
–250
–150
50
150
–50
SENSE VOLTAGE (V
S+
– V
S–
) (mV)
250
1787 G06
Gain vs Temperature
8.195
V
S
= (2.5V + |V
SENSE
|)TO 60V
8.185
V
S+
> V
S–
8.175
0
–10
–20
–30
–40
20
10
30
Gain vs Frequency
V
SENSE
= 10mV
8.135
–40
–20
0
20
40
TEMPERATURE (°C)
60
80
85
1787 G08
–50
0.1k
1k
10k 100k
1M
FREQUENCY (Hz)
10M
100M
1787 G07
1787 G09
LT1787/LT1787HV
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Supply Voltage
75
120
NEGATIVE INPUT SENSE CURRENT (µA)
70
SUPPLY CURRENT (µA)
65
60
55
50
45
V
S+
= V
S–
40
0
T
A
= 85°C
110
100
90
80
70
60
50
40
POSITIVE INPUT SENSE CURRENT (µA)
T
A
= 25°C
T
A
= –40°C
20
30
40
50
10
TOTAL SUPPLY VOLTAGE (V)
Step Response at
V
SENSE
= 0V to 10mV
10mV
0V
80mV
1V
500mV
0V
0V
C
OUT
= 0pF
1787 G12
Step Response at
V
SENSE
= 0V to –128mV
0V
– 100mV
0V
–100mV
0V
– 500mV
– 1V
C
OUT
= 0
U W
1787 G10
1787 G19
Negative Input Sense Current vs
Sense Voltage
60
V
S
= (2.5V + |V
SENSE
|) TO 60V
Positive Input Sense Current vs
Sense Voltage
V
S
= (2.5V + |V
SENSE
|) TO 60V
50
40
30
20
T
A
= 25°C
10
0
–128 –96 –64 –32 0
32 64 96
+
– V
–
) (mV)
SENSE VOLTAGE (V
S
S
T
A
= –40°C
T
A
= 85°C
T
A
= 85°C
T
A
= 25°C
T
A
= –40°C
60
30
–128 –96 –64 –32 0
32 64 96
+
– V
–
) (mV)
SENSE VOLTAGE (V
S
S
128
128
1787 G11
1787 G17
Step Response at
V
SENSE
= 0V to 128mV
100mV
0V
100mV
0V
Step Response at
V
SENSE
= 0V to 128mV
1V
500mV
0V
C
OUT
= 0pF
1787 G18
C
OUT
= 1000pF
1787 G13
Step Response at
V
SENSE
= 0V to –128mV
100mV
0V
– 100mV
Step Response at
V
SENSE
= – 128mV to 128mV
0V
–500mV
–1V
1V
0V
–1V
C
OUT
= 1000pF
1787 G14
C
OUT
= 0
1787 G20
5
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