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LT1787/LT1787HV
Precision, High Side
Current Sense Amplifiers
s
Input Offset Voltage: 75
V (Max)
s
60V Supply Operation (LT1787HV)
s
12-Bit Dynamic Range
s
Operating Current: 60
A
s
User-Selectable External Sense Resistor
s
Bidirectional High Side Current Sensing
s
Unidirectional or Bidirectional Output
s
Input Noise Filtering
s
Available in 8-Lead SO and MSOP Packages
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 40
V
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 60
A and are
available in 8-lead SO and MSOP packages.
s
Battery Monitoring
s
Power Monitoring
s
Portable Phones
s
Cellular Phones
s
Portable Test/Measurement Systems
s
Battery-Operated Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
Input Offset Voltage vs Supply Voltage
12-Bit Dynamic Resolution Unidirectional Output into LTC
1286 ADC
TOTAL SUPPLY VOLTAGE (V)
0
INPUT OFFSET VOLTAGE (
V)
10
20
30
40
1787 TA01b
50
50
40
30
20
10
0
10
20
30
40
50
60
1
8
2
7
3
6
4
5
LT1787HV
R
SENSE
0.0016
1787 TA01
C1
1
F
5V
FIL
+
FIL
R1
15k
C2
0.1
F
V
OUT
= V
BIAS
+ (8 I
LOAD
R
SENSE
)
I = 100A
2.5V TO 60V
TO
LOAD
LT1634-1.25
TO
P
V
REF
V
CC
GND
LTC1286
CS
CLK
D
OUT
+IN
IN
V
BIAS
V
OUT
R
OUT
20k
V
S
V
S
+
DNC
V
EE
APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
DESCRIPTIO
U
2
LT1787/LT1787HV
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
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)
(Notes 1, 2)
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
ORDER PART NUMBER
LT1787CS8
LT1787IS8
LT1787HVCS8
LT1787HVIS8
S8 PART MARKING
1787
1787I
1787HV
787HVI
TOP VIEW
FIL
+
V
S
+
V
BIAS
V
OUT
FIL
V
S
DNC*
V
EE
S8 PACKAGE
8-LEAD PLASTIC SO
1
2
3
4
8
7
6
5
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
S
, V
S
+
Sense Amplifier Supply Voltage Single Supply Operation (LT1787)
q
2.5
36
V
Single Supply Operation (LT1787HV)
q
2.5
60
V
V
SENSE
Input Sense Voltage Full Scale
V
SENSE
= V
S
+
V
S
, V
S
= 10V, V
BIAS
= 5V, A
V
= 8
10%
q
500
mV
V
OS
Input Offset Voltage (S8)
I
OUT
= 0, V
S
Supply = 5V
75
40
75
V
0
C
T
A
70
C
q
135
135
V
40
C
T
A
85
C
q
200
200
V
I
OUT
= 0 (LT1787)
100
100
V
0
C
T
A
70
C
q
160
160
V
40
C
T
A
85
C
q
225
225
V
I
OUT
= 0 (LT1787HV)
100
100
V
0
C
T
A
70
C
q
160
160
V
40
C
T
A
85
C
q
225
225
V
Input Offset Voltage (MS8)
I
OUT
= 0, V
S
Supply = 5V
125
40
125
V
0
C
T
A
70
C
q
230
230
V
40
C
T
A
85
C
q
250
250
V
I
OUT
= 0 (LT1787)
150
150
V
0
C
T
A
70
C
q
250
250
V
40
C
T
A
85
C
q
280
280
V
I
OUT
= 0 (LT1787HV)
150
150
V
0
C
T
A
70
C
q
250
250
V
40
C
T
A
85
C
q
280
280
V
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.
* DO NOT CONNECT
T
JMAX
= 150
C,
JA
= 190
C/ W
1
2
3
4
8
7
6
5
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
FIL
+
V
S
+
V
BIAS
V
OUT
FIL
V
S
DNC*
V
EE
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
* DO NOT CONNECT
T
JMAX
= 150
C,
JA
= 250
C/ W
ORDER PART NUMBER
LT1787CMS8
LT1787IMS8
LT1787HVCMS8
LT1787HVIMS8
MS8 PART MARKING
(Note 4)
LTGM
LTGN
LTKJ
LTKK
3
LT1787/LT1787HV
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
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
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.
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.
V
OS
TC
Temperature Coefficient of V
OS
V
S
Supply = 5V (Note 5)
0.5
2
V/
C
I
OUT(O)
No-Load Output Current Error
V
SENSE
= 0V
4
nA
V
OUT(O)
No-Load Output Voltage Error
V
SENSE
= 0V, V
S
Supply = 5V
600
600
V
(S8)
0
C
T
A
70
C
q
1080
1080
V
40
C
T
A
85
C
q
1600
1600
V
No-Load Output Voltage Error
V
SENSE
= 0V, V
S
Supply = 5V
1000
1000
V
(MS8)
0
C
T
A
70
C
q
1840
1840
V
40
C
T
A
85
C
q
2000
2000
V
g
m
Tranconductance, I
OUT
/ V
SENSE
V
SENSE
= 10mV, 50mV, 100mV, 150mV, 250mV,
400
A/V
V
S
Supply = Total Supply + |V
SENSE
|
A
V
Gain, V
OUT
/ V
SENSE
V
SENSE
= 100mV, V
S
Supply = 5V
q
7.6
8
8.4
V/V
Output Voltage Gain Error
q
5
2
5
%
V
S
PSRR
V
S
Supply Rejection Ratio
V
SENSE
= 0V, V
S
Supply = 2.5V to 36V (LT1787)
q
120
135
dB
V
SENSE
= 0V, V
S
Supply = 2.5V to 60V (LT1787HV)
q
120
135
dB
V
EE
PSRR Negative Supply Rejection Ratio V
SENSE
= 0V, V
S
Supply = 15V, V
BIAS
= 0V,
q
100
130
dB
V
EE
= 1V to 15V (LT1787)
V
SENSE
= 0V, V
S
Supply = 40V, V
BIAS
= 0V,
q
100
130
dB
V
EE
= 1V to 15V (LT1787HV)
V
OS
Change in Input Offset Voltage
V
SENSE
= 0V, V
S
Supply = 36V, V
BIAS
= 0.5V to 25V (LT1787)
q
100
130
dB
V
BIAS
with Change in V
BIAS
Voltage
V
SENSE
= 0V, V
S
Supply = 60V, V
BIAS
= 0.5V to 25V (LT1787HV)
q
100
130
dB
I
S
+
(O)
Positive Input Sense Current
V
SENSE
= 0V
q
10
20
A
I
S
(O)
Negative Input Sense Current
V
SENSE
= 0V
q
50
100
A
I
EE(O)
Negative Supply Current
V
SENSE
= 0V
q
60
120
A
I
OUT
Output Current
V
SENSE
=
128mV
50
A
V
OUT
Output Voltage
V
SENSE
=
128mV, V
S
+
3.3V
V
BIAS
1.024
V
Ripple Rejection
V
S
+
= V
S
= 20V,
V
S
Supply = 1V, f = 1kHz
q
80
88
dB
V
OMIN
Minimum Output Voltage
V
SENSE
= 0V, V
BIAS
= 0V
q
30
45
mV
V
SENSE
= V
S
+
V
S
= 128mV, V
BIAS
= 0V
10
mV
Unipolar Output
V
SENSE
= 2mV, V
BIAS
= 0V
q
32
50
mV
Saturation Voltage
V
SENSE
= 4mV, V
BIAS
= 0V
q
38
55
mV
V
SENSE
= 5mV, V
BIAS
= 0V
q
43
60
mV
V
SENSE
= 6mV, V
BIAS
= 0V
q
49
65
mV
V
OMAX
Maximum Output Voltage
V
S
+
0.75
V
R
G1A,
R
G2A
Input Gain-Setting Resistor
Pin 1 to Pin 2, Pin 7 to Pin 8
1.25
k
R
OUT
Output Resistor
Pin 5 to Pin 6
20
k
(Note 4)
4
LT1787/LT1787HV
Output Voltage vs Sense Voltage
(Unidirectional Mode)
Gain vs Frequency
Gain vs Temperature
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
SENSE VOLTAGE (V
S
+
V
S
) (mV)
0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
120
1787 G07
30
60
90
150
OUPUT VOLTAGE (V)
V
S
= 2.5V TO 60V
T
A
= 40
C TO 85
C
V
BIAS
= V
EE
TEMPERATURE (
C)
40
GAIN (V/
V)
8.195
8.185
8.175
8.165
8.155
8.145
8.135
20
0
20
40
60
1787 G08
80
85
V
S
= (2.5V + |V
SENSE
|)TO 60V
V
S
+
> V
S
V
S
+
< V
S
FREQUENCY (Hz)
0.1k
1k
GAIN (dB)
10k
1M
100k
10M
100M
1787 G09
30
20
10
0
10
20
30
40
50
V
SENSE
= 10mV
Input Offset Voltage vs
Negative Supply Voltage
Output Voltage vs Sense Voltage
(Bidirectional Mode)
Input Offset Voltage vs
Temperature
NEGATIVE SUPPLY VOLTAGE (V)
0
INPUT OFFSET VOLTAGE (
V)
30
20
10
0
10
20
30
5
10
15
20
25
1787 G04
30
T
A
= 25
C
T
A
= 85
C
V
S
+
= V
S
= 2.5V
V
BIAS
= 1V
T
A
= 40
C
TEMPERATURE (
C)
40
INPUT OFFSET VOLTAGE (
V)
50
40
30
20
10
0
10
20
30
40
50
20
0
20
40
60
1787 G05
80
85
V
S
+
= V
S
V
BIAS
= 0V
V
EE
= 1.25V
SENSE VOLTAGE (V
S
+
V
S
) (mV)
250
OUTPUT VOLTAGE (V)
2.5
2.0
1.5
1.0
0.5
V
BIAS
0.5
1.0
1.5
2.0
2.5
150
1787 G06
150
50
50
250
V
S
= 5.5V TO 60V
V
BIAS
= 2.5V
V
EE
= 0V
No Load Output Voltage
vs Supply Voltage
TOTAL SUPPLY VOLTAGE (V)
0
10
OUTPUT VOLTAGE (
V)
20
40
30
50
60
1787 G02
400
300
200
100
0
100
200
300
400
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
V
S
+
= V
S
V
BIAS
= 0V
V
EE
= 1.25V
TOTAL SUPPLY VOLTAGE (V)
0
OUTPUT CURRENT (nA)
10
20
30
40
1787 G03
50
10
8
6
4
2
0
2
4
6
8
10
60
V
BIAS
= 1V
V
EE
= 0V
V
S
+
= V
S
T
A
= 25
C
T
A
= 85
C
T
A
= 40
C
No Load Output Current vs
Supply Voltage
TOTAL SUPPLY VOLTAGE (V)
0
INPUT OFFSET VOLTAGE (
V)
10
20
30
40
1787 G01
50
50
40
30
20
10
0
10
20
30
40
50
60
V
S
+
= V
S
V
BIAS
= 0V
V
EE
= 1.25V
T
A
= 25
C
T
A
= 85
C
T
A
= 40
C
Input Offset Voltage vs
Supply Voltage
5
LT1787/LT1787HV
Supply Current vs Supply Voltage
Negative Input Sense Current vs
Sense Voltage
TOTAL SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
A)
75
70
65
60
55
50
45
40
1787 G10
0
10
20
30
40
50
60
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
V
S
+
= V
S
0V
100mV
0V
500mV
1V
C
OUT
= 1000pF
1787 G14
Step Response at
V
SENSE
= 0V to 128mV
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
SENSE VOLTAGE (V
S
+
V
S
) (mV)
128
NEGATIVE INPUT SENSE CURRENT (
A)
120
110
100
90
80
70
60
50
40
30
64
0
32
1787 G11
96
32
64
96
128
V
S
= (2.5V + |V
SENSE
|) TO 60V
T
A
= 25
C
T
A
= 85
C
T
A
= 40
C
SENSE VOLTAGE (V
S
+
V
S
) (mV)
128
POSITIVE INPUT SENSE CURRENT (
A)
60
50
40
30
20
10
0
64
0
32
1787 G17
96
32
64
96
128
V
S
= (2.5V + |V
SENSE
|) TO 60V
T
A
= 85
C
T
A
= 40
C
T
A
= 25
C
Positive Input Sense Current vs
Sense Voltage
Step Response at
V
SENSE
= 0V to 10mV
Step Response at
V
SENSE
= 0V to 128mV
10mV
0V
80mV
0V
C
OUT
= 0pF
1787 G12
100mV
0V
1V
500mV
0V
C
OUT
= 1000pF
1787 G13
Step Response at
V
SENSE
= 0V to 128mV
100mV
0V
1V
500mV
0V
C
OUT
= 0pF
1787 G18
Step Response at
V
SENSE
= 0V to 128mV
0V
100mV
0V
500mV
1V
C
OUT
= 0
1787 G19
Step Response at
V
SENSE
= 128mV to 128mV
0V
100mV
1V
100mV
0V
1V
C
OUT
= 0
1787 G20
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