MAX9934 Maxim, MAX9934 Datasheet - Page 12

• Manufacturer Part Number: MAX9934
• Description: The MAX9934 high-precision, low-voltage, high-side current-sense amplifier is ideal for both bidirectional (charge/discharge) and unidirectional current measurements in battery-powered portable and laptop devices
• Manufacturer: Maxim

High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
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
Figure 4. Typical Application Circuit Showing Chip-Select Multiplexing
12
______________________________________________________________________________________
V
V
V
IN1
IN2
IN3
UNIDIRECTIONAL OPERATION
Chip-Select Functionality
-0.1V ≤ V
for Multiplexed Systems
-0.1V ≤ V
-0.1V ≤ V
CM
CM
CM
≤ 5.5V
≤ 5.5V
≤ 5.5V
R
R
R
I
I
I
LOAD1
SENSE
LOAD2
LOAD3
SENSE
SENSE
MAX9934
MAX9934
MAX9934
V
V
V
CC
CC
CC
= 3.3V
= 3.3V
= 3.3V
0.1µF
0.1µF
0.1µF
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
10kΩ
OUT3
V
OUT1
OUT2
OUT
(OPTIONAL)
CS1
CS2
CS3
MICROCONTROLLER
OUT
ADC
to a midrail voltage V
BIAS
.