LT1490/LT1491
Dual and Quad
Micropower Rail-to-Rail
Input and Output Op Amps
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FEATURES
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DESCRIPTIO
Rail-to-Rail Input and Output
Single Supply Input Range: – 0.4V to 44V
Micropower: 50µA/Amplifier Max
µ
MSOP Package
Specified on 3V, 5V and ±15V Supplies
High Output Current: 20mA
Output Drives 10,000pF with Output Compensation
Reverse Battery Protection to 18V
No Supply Sequencing Problems
High Voltage Gain: 1500V/mV
High CMRR: 98dB
No Phase Reversal
Gain Bandwidth Product: 200kHz
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APPLICATIO S
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Battery- or Solar-Powered Systems
Portable Instrumentation
Sensor Conditioning
Supply Current Sensing
Battery Monitoring
Micropower Active Filters
4mA to 20mA Transmitters
, LTC and LT are registered trademarks of Linear Technology Corporation.
The dual LT ®1490 and quad LT1491 op amps operate on all
single and split supplies with a total voltage of 2V to 44V
drawing only 40µA of quiescent current per amplifier. These
amplifiers are reverse supply protected; they draw no current
for reverse supply up to 18V. The input range of the LT1490/
LT1491 includes both supplies and the output swings to both
supplies. Unlike most micropower op amps, the LT1490/
LT1491 can drive heavy loads; their rail-to-rail outputs drive
20mA. The LT1490/LT1491 are unity-gain stable and drive all
capacitive loads up to 10,000pF when optional 0.22µF and
150Ω compensation is used.
The LT1490/LT1491 have a unique input stage that operates and remains high impedance when above the positive
supply. The inputs take 44V both differential and common
mode even when operating on a 3V supply. Built-in resistors protect the inputs for faults below the negative supply
up to 22V. There is no phase reversal of the output for inputs
22V below V – or 44V above V –, independent of V +.
The LT1490 dual op amp is available in the 8-pin MSOP,
SO and PDIP packages. The quad LT1491 is available in
the 14-pin SO and PDIP packages.
For new designs it is recommended that the LT1490A/
LT1491A be used instead of the LT1490/LT1491. See the
LT1490A/LT1491A data sheet for details.
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TYPICAL APPLICATIO
Battery Monitor
RS
0.2Ω
CHARGER
VOLTAGE
RA
2k
RA'
2k
IBATT
+
A
1/4 LT1491
Q1
2N3904
–
C
1/4 LT1491
–
LOGIC
+
RB
2k
RB'
2k
LOAD
+
Q2
2N3904
–
+
+
RG
10k
VBATT = 12V
S1
IBATT =
LOGIC HIGH (5V) = CHARGING
LOGIC LOW (0V) = DISCHARGING
B
1/4 LT1491
V
VOUT
= OUT AMPS
(RS)(RG /RA)(GAIN) GAIN
D
1/4 LT1491
VOUT
–
10k
90.9k
S1 = OPEN, GAIN = 1
S1 = CLOSED, GAIN = 10
RA = RB
VS = 5V, 0V
1490/91 TA01
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