Rainbow Electronics MAX9920 - Manual (Page 14)

Uni-/Bidirectional Operation
The MAX9918/MAX9919/MAX9920 support both unidi-
rectional and bidirectional operation. The devices oper-
ate in unidirectional mode with V
REFIN
= GND. The
output is then referenced to ground and the output volt-
age V
OUT is proportional to the positive voltage drop
(V SENSE ) from RS+ to RS- (Figure 1).
The MAX9918/MAX9919 operate in bidirectional mode
by application of a low-source impedance reference
voltage in the 0V to V
CC - 1.9V range, (typically V CC /2),
to REFIN. For the MAX9920, the reference voltage range
is 0V to V
CC - 2.4V (typically V CC /2). The output voltage
V
OUT
relative to V
REFIN
is then proportional to the
±V SENSE voltage drop from RS+ to RS- (Figure 2).
MAX9918/MAX9919/MAX9920
-20V to +75V Input Range, Precision
Uni-/Bidirectional, Current-Sense Amplifiers
14 ______________________________________________________________________________________
I DISCHARGE
R SENSE
LOAD
TO ADC V CC
GND
RS+ RS-
REFIN
OUT
30mV 10mV 20mV 20mV 0
DISCHARGE
CURRENT
0.9V
3.6V
2.7V
G = 90V/V
5V
1.8V
SHDN
MAX9919N
V SENSE
V OUT
Figure 1. Unidirectional Operation
I DISCHARGE
R SENSE
I CHARGE
LOAD
TO ADC
2.5V
V CC
GND
RS+ RS-
REFIN
OUT
-20mV 10mV 20mV 0
DISCHARGE
CURRENT
CHARGE
CURRENT
-1.8V
1.8V
0.9V
G = 90V/V
V SENSE
5V
-0.9V
-10mV
SHDN
V OUT - V REFIN
MAX9919N
Figure 2. Bidirectional Operation