AD8207WBRZ-R7 datasheet(14/16 Pages) AD

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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

VREF1 +VS OUT

–IN

GND

CONTROLLER

VREF2RANGE

2.5V

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+

V–

OPTIONAL

PART FOR

OVERCURRENT

PROTECTION AND

FAST (DIRECT)

SHUTDOWN OF

POWER STAGE

AD8207

CONTROLLER

Figure 34. 3-Phase Motor Control

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