LT1498/LT1499
14989fg
24
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2009
LT 0410 REV G • PRINTED IN USA
RELATED PARTS
TYPICAL APPLICATION
Bidirectional Current Sensor
A bidirectional current sensor for battery-powered sys-
tems is shown in Figure 3. Two outputs are provided: one
proportional to charge current, the other proportional
to discharge current. The circuit takes advantage of the
LT1498’s rail-to-rail input range and its output phase
reversal protection. During the charge cycle, the op amp
A1 forces a voltage equal to (I
L
)(R
SENSE
) across R
A
. This
voltage is then amplifi ed at the Charge Out by the ratio of
R
B
over R
A
. In this mode, the output of A2 remains high,
keeping Q2 off and the Discharge Out low, even though
the (+) input of A2 exceeds the positive power supply.
During the discharge cycle, A2 and Q2 are active and the
operation is similar to the charge cycle.
Figure 3. Bidirectional Current Sensor
–
+
–
+
A1
1/2 LT1498
A2
1/2 LT1498
Q2
MTP23P06
V
O
= I
L
= 1V/A
FOR R
A
= 1k, R
B
= 10k
R
SENSE
DISCHARGE
OUT
CHARGE
OUT
Q1
MTP23P06
R
A
R
B
R
B
R
A
R
A
R
A
V
BATTERY
V
BATTERY
14989 F03
DISCHARGE
I
L
CHARGE
R
A
R
SENSE
0.1Ω
R
B
()
V
O
I
L
PART NUMBER DESCRIPTION COMMENTS
LT C
®
1152 Rail-to-Rail Input and Output, Zero-Drift Op Amp High DC Accuracy, 10μV V
OS(MAX)
, 100nV/°C Drift, 1MHz GBW, 1V/μs
Slew Rate, Max Supply Current 2.2mA
LT1211/LT1212 Dual/Quad 14MHz, 7V/μs, Single Supply Precision Op Amps Input Common Mode Includes Ground, 275μV V
OS(MAX)
, 6μV/°C Max
Drift, Max Supply Current 1.8mA per Op Amp
LT1213/LT1214 Dual/Quad 28MHz, 12V/μs, Single Supply Precision Op Amps Input Common Mode Includes Ground, 275μV V
OS(MAX)
, 6μV/°C Max
Drift, Max Supply Current 3.5mA per Op Amp
LT1215/LT1216 Dual/Quad 23MHz, 50V/μs, Single Supply Precision Op Amps Input Common Mode Includes Ground, 450μV V
OS(MAX)
, Max Supply
Current 6.6mA per Op Amp
LT1366/LT1367 Dual/Quad Precision, Rail-to-Rail Input and Output Op Amps 475μV V
OS(MAX)
, 400kHz GBW, 0.13V/μs Slew Rate, Max Supply
Current 520μA per Op Amp
LT1490/LT1491 Dual/Quad Micropower, Rail-to-Rail Input and Output Op Amps Max Supply Current 50μA per Op Amp, 200kHz GBW, 0.07V/μs Slew
Rate, Operates with Inputs 44V Above V
–
Independent of V
+
LT1884/LT1885 Dual/Quad, Rail-to-Rail Output Picoamp Input Precision Op Amps I
CC
= 650μA, V
OS
< 50μV, I
B
< 400pA
