Datasheet

AD8207
Rev. 0 | Page 14 of 16
APPLICATIONS INFORMATION
MOTOR CONTROL
3-Phase Motor Control
The AD8207 is ideally suited for monitoring current in 3-phase
motor applications.
The 150 kHz typical bandwidth of the AD8207 allows for
instantaneous current monitoring. Additionally, the typical
low offset drift of 500 nV/°C means that the measurement
error between the two motor phases will be at a minimum
over temperature. The AD8207 rejects PWM input common-
mode voltages in the range of −4 V to +65 V (with a 5 V
supply). Monitoring the current on the motor phase allows
for sampling of the current at any point and allows for
diagnostic information such as a short to GND and battery.
Refer to Figure 34 for a typical phase current measurement
setup with the AD8207.
H-Bridge Motor Control
Another typical application for the AD8207 is as part of
the control loop in H-bridge motor control. In this case, the
shunt resistor is placed in the middle of the H-bridge (see
Figure 33) so that it can accurately measure current in both
directions by using the shunt available at the motor. This is
a better solution than a ground referenced op amp because
ground is not typically a stable reference voltage in this type
of application. The instability of the ground reference causes
inaccuracies in the measurements that could be made with a
simple ground referenced op amp. The AD8207 measures
current in both directions as the H-bridge switches and the
motor changes direction. The output of the AD8207 is config-
ured in an external referenced bidirectional mode (see the
Bidirectional Operation section).
AD8207
+IN
SHUNT
MOTOR
V
REF
1
+V
S
OUT
–IN GND
5V
CONTROLLER
V
REF
2RANGE
5V
2.5V
09160-020
Figure 33. H-Bridge Motor Control Application
AD8207
BIDIRECTIONAL CURRENT MEASUREMENT
REJECTION OF HIGH PWM COMMON-MODE VOLTAGE (–4V TO +65V)
AMPLIFICATION
HIGH OUTPUT DRIVE
AD8214
INTERFACE
CIRCUIT
V
+
I
U
I
V
I
W
V–
OPTIONAL
PART FOR
OVERCURRENT
PROTECTION AND
FAST (DIRECT)
SHUTDOWN OF
POWER STAGE
AD8207
CONTROLLER
5V 5V
M
09160-017
Figure 34. 3-Phase Motor Control