Current Sense Solutions
InfoCard 27
Linear Technology Offers a Complete Range of High Side and Low Side Current
Sensing Solutions
LT1787/LT1787HV Precision High Side Current Sense Amplifier
12-Bit Dynamic Resolution Unidirectional Output into LTC1286 ADC
■
■
■
■
■
■
■
■
■
TO
LOAD
Input Offset Voltage: 75µV (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
I = 100A
1
RSENSE
0.0016Ω
8
FIL+
LT1787HV +
–
VS 7
2 VS
3
4
FIL–
DNC
VBIAS 6
ROUT
20k
VEE
5
VOUT
C2
0.1µF
2.5V TO 60V
R1
15k
C1
1µF
5V
VREF VCC
CS
+IN
LTC1286 CLK
–IN
D
GND OUT
TO µP
LT1634-1.25
VOUT = VBIAS + (8 • ILOAD • RSENSE)
Charge/Discharge Current Monitor on
Single Supply with VBIAS = 1.25V
1
FIL–
2
VS–
3
4
FIL+
LT1787HV
3.3V
TO
60V
C1
1µF
8
3.3V
VS+ 7
20k
5%
VBIAS 6
DNC
OUTPUT VOLTAGE – OUTPUT BIAS VOLTAGE (V)
IS
RSENSE
TO
CHARGER/
LOAD
Single Supply Output Voltage with VBIAS = 1.25V
ROUT
VEE
C2
1µF
5
VOUT
LT1634-1.25
C3
1000pF
OUTPUT
1.5
1.0
VS = 3.3V TO 60V
TA = – 40°C TO 85°C
0.5
0
–0.5
–1.0
–1.5
–128 –96 –64 –32 0
32 64 96
SENSE VOLTAGE (VS+ – VS–) (mV)
128
Precision Low Side Current Sensing with the LTC2050 Zero Drift Amplifier
■
5V
■
IS
3
■
+
7
LTC2050
2
RSENSE
–
8
■
VOUT
4
■
■
50k
50Ω
■
■
■
■
VOUT = 1000 • (IS • RSENSE)
■
SOT-23 Package
Maximum Offset Voltage of 3µV
Maximum Offset Voltage Drift of 30nV/°C
Noise: 1.5µVP-P (0.1Hz to 10Hz Typ)
Voltage Gain: 140dB (Typ)
PSRR: 130dB (Typ)
CMRR: 130dB (Typ)
Supply Current: 0.8mA (Typ)
Single Supply Operation: 2.7V to 10V
Extended Common Mode Input Range
Output Swings Rail-to-Rail
, LTC and LT are registered trademarks of Linear Technology Corporation.
Linear Technology Corporation • 1630 McCarthy Blvd. • Milpitas, CA 95035-7417 • (408) 432-1900 • www.linear-tech.com • Literature Only: 1-800-4-LINEAR
Current Sense Solutions
InfoCard 27
High Side Current Sensing Using Linear Technology’s Over-The-TopTM Op Amps
LTC’s Unique Over-The-Top Input Stage Allows Both Inputs
to Operate Above the Positive Supply Rail
5V TO 44V
R1
200Ω
VS
UP TO 88V
IS
RS
R
R
5V
RS
0.2Ω
+
+
Q1
2N3904
VOUT
(0V TO 4.3V)
R2
2k
LT1637
–
ILOAD
LOAD
ILOAD =
VOUT
(RS)(R2/R1)
–
LT1637
R′
V+
R′
VOUT
R′
R
VOUT = IS • RS •
Battery Monitor
RS
0.2Ω
CHARGER
VOLTAGE
RA
2k
+
A
1/4 LT1491A
RA'
2k
IBATT
Q1
2N3904
–
C
1/4 LT1491A
–
LOGIC
+
RB
2k
+
Q2
2N3904
–
LOAD
+
+
RG
10k
VBATT = 12V
S1
IBATT =
LOGIC HIGH (5V) = CHARGING
LOGIC LOW (0V) = DISCHARGING
B
1/4 LT1491A
R B'
2k
VOUT
V
= OUT AMPS
(RS)(RG /RA)(GAIN) GAIN
D
1/4 LT1491A
VOUT
–
10k
90.9k
S1 = OPEN, GAIN = 1
S1 = CLOSED, GAIN = 10
RA = RB
VS = 5V, 0V
Over-The-Top Op Amps
PART NUMBER
LT1490A/LT1491A
MAX INPUT CM
VSUPPLY
ISUPPLY (MAX)
GBW (TYP)
VOS (MAX)
IOUT
PACKAGE
44V
2V to 44V
50µA
200kHz
200µV
20mA
MS8, SO-8, S14
COMMENTS
Dual/Quad
LT1636
44V
2V to 44V
55µA
200kHz
225µV
18mA
MS8, SO-8
Single
LT1637
44V
2V to 44V
250µA
1.1MHz
350µV
25mA
MS8, SO-8
Single
LT1638/LT1639
44V
2.5V to 44V
230µA
1.2MHz
600µV
25mA
MS8, SO-8, S14
Dual/Quad
LT1782
18V
2.5V to 18V
55µA
200kHz
800µV
18mA
SOT-23
Single
LT1783
18V
2.5V to 18V
300µA
1.2MHz
800µV
18mA
SOT-23
Single
All Over-The-Top Op Amps from Linear Technology Also Offer Rail-to-Rail Inputs and Outputs
Over-The-Top is a trademark of Linear Technology Corporation.
Linear Technology Corporation • 1630 McCarthy Blvd. • Milpitas, CA 95035-7417 • (408) 432-1900 • www.linear-tech.com • Literature Only: 1-800-4-LINEAR
ic27 ©2000 LT/TP 0600 4K