LT1638 LINER [Linear Technology], LT1638 Datasheet - Page 12

• Manufacturer Part Number: LT1638
• Description: 1.2MHz, 0.4V/us Over-The-TopTM Micropower Rail-to-Rail Input and Output Op Amps
• Manufacturer: LINER [Linear Technology]

LT1638/LT1639
TYPICAL
The battery monitor in Figure 5 also demonstrates the
LT1638’s ability to operate with its inputs above the
positive rail. In this application, a conventional amplifier
would be limited to a battery voltage between 5V and
ground, but the LT1638 can handle battery voltages as
high as 44V. When the battery is charging, Amp B senses
the voltage drop across R
Q2 to drain sufficient current through R
input of Amp B. Likewise, Amp A and Q1 form a closed
RELATED PARTS
PART NUMBER
LT1078/LT1079
LT2078/LT2079
LT1178/LT1179
LT2178/LT2179
LT1366/LT1367
LT1490/LT1491
LT1636
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] FAX: [phone] www.linear-tech.com
APPLICATION
CHARGER
VOLTAGE
DESCRIPTION
Dual/Quad 55 A Max, Single Supply, Precision Op Amps
Dual/Quad 17 A Max, Single Supply, Precison Op Amps
Dual/Quad Precision, Rail-to-Rail Input and Output Op Amps
Dual/Quad Over-The-Top Micropower, Rail-to-Rail Input and
Output Op Amps
Single Over-The-Top Micropower Rail-to-Rail Input and Output
Op Amp
S
I
BATT
LOAD
. The output of Amp B causes
=
R
S
I
(R
BATT
, 0.2
S
)(R
U
+
G
V
/R
OUT
A
R
R
V
)(GAIN)
R A , 2k
R
BATT
A
B
B
B
',
'
, 2k
, 2k
2k
to balance the
= 12V
=
V
GAIN
OUT
Figure 5. Battery Monitor
1/4 LT1639
1/4 LT1639
+
–
+
–
AMPS
A
B
2N3904
S1
S1 = OPEN, GAIN = 1
S1 = CLOSED, GAIN = 10
loop when the battery is discharging. The current through
Q1 or Q2 is proportional to the current in R
current flows into R
D buffers and amplifies the voltage across R
compares the output of Amp A and Amp B to determine
the polarity of current through R
V
is 1V/100mA and currents as low as 500 A can be
measured.
Q2
OUT
10k
2N3904
with S1 open is 1V/A. With S1 closed the scale factor
Q1
COMMENTS
Input/Output Common Mode Includes Ground, 70 V V
and 2.5 V/ C Drift (Max), 200kHz GBW, 0.07V/ s Slew Rate
Input/Output Common Mode Includes Ground, 70 V V
and 4 V/ C Drift (Max), 85kHz GBW, 0.04V/ s Slew Rate
475 V V
Single Supply Input Range: – 0.4V to 44V, Micropower 50 A
per Amplifier, Rail-to-Rail Input and Output, 200kHz GBW
55 A Supply Current, V
Independent of V
R
10k
G
OS(MAX)
1/4 LT1639
1/4 LT1639
+
–
+
–
G
LOGIC HIGH (5V) = CHARGING
LOGIC LOW (0V) = DISCHARGING
, 500V/mV A
CC
R
V
and is converted into a voltage. Amp
C
D
A
S
; MSOP Package, Shutdown Function
= R
= 5V, 0V
90.9k
B
CM
Extends 44V above V
VOL(MIN)
LINEAR TECHNOLOGY CORPORATION 1998
16389f LT/TP 1098 4K • PRINTED IN USA
1638/39 F05
S
. The scale factor for
, 400kHz GBW
LOGIC
V
OUT
EE
,
S
G
. Amp C
and this
OS(MAX)
OS(MAX)