MAX4372 Maxim, MAX4372 Datasheet - Page 6

• Manufacturer Part Number: MAX4372
• Description: Low-Cost / SOT23 / Micropower / High-Side Current-Sense Amplifier with Voltage Output
• Manufacturer: Maxim

Low-Cost, SOT23, Micropower, High-Side
Current-Sense Amplifier with Voltage Output
The MAX4372 high-side current-sense amplifier fea-
tures a 0 to +28V input common-mode range that is
independent of supply voltage. This feature allows the
monitoring of current flow out of a battery in deep dis-
charge, and also enables high-side current sensing at
voltages far in excess of the supply voltage (V
Current flows through the sense resistor, generating a
sense voltage (Figure 1). Since A1’s inverting input is
high impedance, the voltage on the negative terminal
equals V
match its negative terminal; therefore, the voltage
across R
current to flow through R
transistor and current mirror amplify the current by a
factor of . This makes the current flowing out of the
current mirror equal to:
A2’s positive terminal presents high impedance, so this
current flows through R
R1 and R2 set the closed-loop gain for A2, which
amplifies V
The gain of the device equals:
The MAX4372 operates over a wide variety of current
ranges with different sense resistors. Table 1 lists com-
mon resistor values for typical operation of the
MAX4372.
6
_______________Detailed Description
__________Applications Information
SOT23-5
_______________________________________________________________________________________
—
1
2
3
4
5
V
OUT
V
IN
G1
V
SENSE
PIN
2+
Recommended Component Values
OUT
= R
- V
(V
, yielding:
V
IN
SENSE
2+
2, 5, 7
GD
SO
= R
3
4
1
8
6
- V1-) equals V
I
= R
M
·
GD
=
. A1 forces its positive terminal to
GD
· V
GD
·
V
SENSE
G1
SENSE
, with the following result:
(1 + R2 / R1) / R
NAME
· V
GND
OUT
RS+
N.C.
V
equal to V
RS-
CC
SENSE
/ R
/ R
SENSE
G1
G1
/ R
(1 + R2 / R1)
Ground
Output Voltage. V
Supply Voltage
Power Connection to the External Sense Resistor
Load-Side Connection to the External Sense Resistor
No Connection. Not internally connected.
SENSE
G1
. This creates a
G1
/ R
CC
G1
).
. The
OUT
is proportional to the magnitude of V
Given the gain and maximum load current, select
R
and V
currents more accurately, use a high value for R
A higher value develops a higher sense voltage, which
overcomes offset voltage errors of the internal current
amplifier.
In applications monitoring very high current, ensure
R
resistor’s rated power dissipation is exceeded, its value
may drift or it may fail altogether, causing a differential
voltage across the terminals in excess of the absolute
maximum ratings.
Figure 1. Functional Diagram
SENSE
SENSE
+2.7V
+28V
TO
OUT
V
OUT
such that V
CC
is able to dissipate its own I
FUNCTION
CURRENT
MIRROR
does not exceed +10V. To measure lower
MAX4372T/F/H
I
CC
M
R2
A1
A2
- V
OUT
V1+
V1-
SENSE
V2+
V2-
does not exceed +0.25V
Pin Description
R G1
R
R GD
R1
G2
Choosing R
(V
RS+
GND
RS+
RS-
2
R losses. If the
- V
R
RS-
SENSE
I
LOAD
0 TO +28V
).
LOAD
V
TO
IN
SENSE
SENSE
V
SENSE
.