Datasheet

MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
10
Maxim Integrated
Detailed Description
The MAX9934 high-side, current-sense amplifier moni-
tors current through an external current-sense resistor
by amplifying the voltage across the resistor (V
SENSE
)
to create an output current (I
OUT
). An output voltage
(V
OUT
) then develops across the external output resis-
tor (R
OUT
). See the Typical Operating Circuit .
The MAX9934 uses precision amplifier design tech-
niques to achieve a low-input offset voltage of less than
10µV. These techniques also enable extremely low-input
offset voltage drift over time and temperature and
achieve gain error of less than 0.25%. The precision V
OS
specification allows accurate current measurements with
a low-value current-sense resistor, thus reducing power
dissipation in battery-powered systems, as well as load-
regulation issues in low-voltage DC power supplies.
The MAX9934 high-side current-sense amplifier fea-
tures a -0.1V to +5.5V input common-mode range that
is independent of supply voltage (V
CC
). This ability to
sense at voltages beyond the supply rail allows the
monitoring of currents out of a power supply even in a
shorted condition, while also enabling high-side current
sensing at voltages greater than the MAX9934 supply
Pin Description
PIN/BUMP
UCSP µMAX
NAME FUNCTION
A1 1 V
CC
Power Supply
A2 2 OUT
Current Output. OUT provides an output current proportional to input V
SENSE
. Connect an
external resistor (R
OUT
) from OUT to GND for unidirectional sensing or to an external reference
voltage for bidirectional sensing.
A3 3 GND Ground
B1 8 RS+ Sense Resistor Power Side Connection
B2 7 RS- Sense Resistor Load Side Connection
B3 6 CS
Chip-Select Input. Drive CS high to enable OUT, drive CS low to put OUT in a high-impedance
state.
— 4, 5 N.C. No Connection. Not internally connected.
% FINAL VALUE
V
OUT
±1V STEP
t
S
2V
1V
t
S
% FINAL VALUE
V
SENSE
Figure 1. Output Settling Time
CS
OUT
GND
RS-
RS+
V
CC
*R
GAIN
G
m
MAX9934
G
m
*R
GAIN
= 40Ω FOR THE MAX9934T AND
R
GAIN
= 200Ω FOR THE MAX9934F.
Functional Diagram