Datasheet

MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
12
Maxim Integrated
Chip-Select Functionality
for Multiplexed Systems
The MAX9934 features a CS that can be used to dese-
lect the output current - source achieving a high-imped-
ance output with 0.1nA leakage current. Thus, different
supply voltages can be used to power different
MAX9934 devices that are multiplexed on the same
bus. This technique makes it possible for advanced
current monitoring and power-management schemes to
be implemented when a limited number of ADC chan-
nels are available.
In a multiplexed arrangement, each MAX9934 is typi-
cally placed near the load being monitored and all
amplifier outputs are connected in common to a single
load resistor located adjacent to the monitoring ADC.
This resistor is terminated to the ADC ground reference
as shown in Figure 4 for unidirectional applications.
Figure 5 shows a bidirectional multiplexed application.
Terminating the external resistor at the ground refer-
ence of the ADC minimizes errors due to ground shift
as discussed in the
Advantages of Current-Output
Architecture section.
The MAX9934 is capable of both sourcing and sinking
current from OUT, and thus can be used as a precision
bidirectional current-sense amplifier. To enable this
functionality, terminate R
OUT
to a midrail voltage V
BIAS
.
V
CC
= 3.3V
V
CC
= 3.3V
V
CC
= 3.3V
R
SENSE
-0.1V ≤ V
CM
≤ 5.5V
R
SENSE
-0.1V ≤ V
CM
≤ 5.5V
R
SENSE
-0.1V ≤ V
CM
≤ 5.5V
MAX9934
MAX9934
MAX9934
10kΩ
(OPTIONAL)
ADC
CS3
CS2
CS1
MICROCONTROLLER
V
IN1
V
IN2
V
IN3
I
LOAD3
I
LOAD2
I
LOAD1
V
OUT
0.1µF
0.1µF
0.1µF
OUT3
OUT2
OUT1
UNIDIRECTIONAL OPERATION
Figure 4. Typical Application Circuit Showing Chip-Select Multiplexing