Datasheet

MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
13
Maxim Integrated
In Figure 5, V
OUT
is equal to V
BIAS
when the sum of all
outputs is zero. For positive input-sense voltages, the
MAX9934 sources current causing its output voltage to
rise above V
BIAS
. For negative input-sense voltages,
the MAX9934 sinks current causing its output voltage to
be lower than V
BIAS
, thus allowing bidirectional current
sensing.
Since the ADC reference voltage, V
REF
, determines the
full-scale reading, a common choice for V
BIAS
is
V
REF
/2. The current output makes it possible to use a
simple resistor-divider from V
REF
to GND to generate
V
BIAS
. The output resistance for gain calculation is the
parallel combination of the two resistors. For example, if
two equal value resistors, R, are used to generate a
V
BIAS
= V
REF
/2, the output termination resistance for
gain calculation is R
OUT
= R/2. See Figure 5.
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
R
10kΩ
ADC
V
REF
CS2
CS1
MICROCONTROLLER
CS
CS
CS
TO EXTERNAL
REFERENCE
VOLTAGE
10kΩ
R
CS3
(OPTIONAL)
V
IN1
V
IN2
V
IN3
I
LOAD3
I
LOAD2
I
LOAD1
V
OUT
OUT3
OUT2
OUT1
R
OUT
=
R
2
Figure 5. Bidirectional Multiplexed Operation