Datasheet

MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
14
Maxim Integrated
A MAX9934 can be deselected by either forcing V
CS
low as shown in Figures 4 and 5, or by making V
CC
=
0V as shown in Figure 6. In all these conditions, the
MAX9934 maintains a high-impedance output with
0.1nA (typ) leakage current. In this state, OUT can rise
above V
CC
if necessary. Thus, different supply voltages
can be used to power different MAX9934 devices that
are multiplexed on the same OUT bus. Multiplexing by
forcing the MAX9934 to be powered down (V
CC
= 0V)
reduces its supply current to zero to help extend bat-
tery life in portable applications.
Choosing R
SENSE
and R
OUT
In the current-sense application, the monitored load
current (I
LOAD
) develops a sense voltage (V
SENSE
)
across a current-sense resistor (R
SENSE
). The
MAX9934 sources or sinks an output current that is pro-
portional to V
SENSE
. Finally, the MAX9934 output cur-
rent is provided to an output resistor (R
OUT
) to develop
an output voltage across R
OUT
that is proportional to
the sensed load current.
V
CC
= 3.3V
R
SENSE
-0.1V ≤ V
CM
≤ 5.5V
MAX9934
R
OUT
10kΩ
(OPTIONAL)
ADC
CS2
CS1
MICROCONTROLLER
CS
CS3
V
CC
= 3.3V
R
SENSE
-0.1V ≤ V
CM
≤ 5.5V
MAX9934
CS
V
CC
= 3.3V
R
SENSE
-0.1V ≤ V
CM
≤ 5.5V
MAX9934
CS
1/4 MAX4737
1/4 MAX4737
1/4 MAX4737
V
IN1
V
IN2
V
IN3
I
LOAD1
OUT3
OUT2
OUT1
0.1µF
0.1µF
0.1µF
I
LOAD3
I
LOAD2
Figure 6. Multiplexed Amplifiers with Power Saving