MAX472ESA-T Maxim Integrated, MAX472ESA-T Datasheet - Page 9

• Manufacturer Part Number: MAX472ESA-T
• Description: Special Purpose Amplifiers
• Manufacturer: Maxim Integrated
• Series: MAX471, MAX472r

Specifications of MAX472ESA-T

• Number Of Channels: Single
• Input Offset Voltage: 0.14 mV
• Operating Supply Voltage: 5 V, 9 V, 12 V, 15 V
• Supply Current: 0.02 mA
• Maximum Power Dissipation: 471 mW
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Supply Voltage - Max: 36 V
• Supply Voltage - Min: 3 V

for current summing. A single scaling resistor is
required when summing OUT currents from multiple
devices (Figure 3). Current can be integrated by con-
necting OUT to a capacitive load.
The current at OUT indicates magnitude. The SIGN out-
put indicates the current’s direction. Operation of the
SIGN comparator is straightforward. When Q1 (Figures
1 and 2) conducts, the output of A1 is high while A2’s
output is zero. Under this condition, a high SIGN output
indicates positive current flow (from RS+ to RS-). In bat-
tery-operated systems, this is useful for determining
whether the battery is charging or discharging. The
SIGN output may not correctly indicate if the load cur-
rent is such that I
SIGN output accurately indicates the direction of cur-
rent flow for load currents greater than 7mA.
SIGN is an open-collector output (sinks current only),
allowing easy interface with logic circuits powered from
any voltage. Connect a 100kΩ pull-up resistor from
SIGN to the logic supply. The convention chosen for
the polarity of the SIGN output ensures that it draws no
current when the battery is being discharged. If current
direction is not needed, float the SIGN pin.
Precision, High-Side
Current-Sense Amplifiers
Figure 3. Paralleling MAX471s to Sense Higher Load Current
8
_______________________________________________________________________________________
3V
TO
36V
RS+
RS+
RS+
RS+
OUT
MAX471
MAX471
GND
GND
is less than 3.5µA. The MAX471’s
SIGN
SIGN
OUT
OUT
RS-
RS-
RS-
RS-
1k
LOGIC
SUPPLY
SIGN Output
100k
V
TO LOAD/
CHARGER
OUT
When SHDN is high, the MAX471/MAX472 are shut
down and consume less than 18µA. In shutdown mode,
SIGN is high impedance and OUT turns off.
The MAX471 obtains its power from the RS- pin. This
includes MAX471 current consumption in the total sys-
tem current measured by the MAX471. The small drop
across R
mance.
Since OUT delivers a current, an external voltage gain-
setting resistor (R
pin in order to get a voltage. R
MAX471. RG1 and RG2 are factory trimmed for an out-
put current ratio (output current to load current) of
500µA/A. Since they are manufactured of the same
material and in very close proximity on the chip, they
provide a high degree of temperature stability. Choose
R
- 1.5V (see the Current Output section).
Figure 4. MAX472 Standard Application Circuit
BATTERY
__________Applications Information
SOURCE
OUT
POWER
OR
for the desired full-scale output voltage up to RS-
SENSE
3V
TO
36V
does not affect the MAX471’s perfor-
OUT
1
2
3
4
RG1
SHDN
N.C.
RG1
GND
to ground) is required at the OUT
MAX472
R
SENSE
SENSE
SIGN
OUT
V
RG2
CC
Resistor Selection
RG2
8
7
6
5
is internal to the
TO LOAD/CHARGER
Shutdown
MAX471
100k
R
SUPPLY
OUT
LOGIC