Data Sheet

AD8417-2

APPLICATIONS INFORMATION

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Rev. 0 | 13 of 15

MOTOR CONTROL

3-Phase Motor Control

The AD8417-2 is ideally suited for monitoring current in 3-phase

motor applications.

The 250 kHz typical bandwidth of the AD8417-2 provides instanta-

neous current monitoring. Additionally, the typical low offset drift

of 0.1 µV/°C means that the measurement error between the two

motor phases is at a minimum over temperature. The AD8417-2

rejects PWM input common-mode voltages in the −2 V to +70 V

(with a 5 V supply) range. Monitoring the current on the motor

phase allows sampling of the current at any point and provides

diagnostic information, such as a short to GND and the battery. See

Figure 33 for the typical phase current measurement setup with the

AD8417-2.

H-Bridge Motor Control

Another typical application for the AD8417-2 is to form part of

the control loop in H-bridge motor control. In this case, place the

shunt resistor in the middle of the H-bridge to accurately measure

current in both directions by using the shunt available at the motor

(see Figure 32). Using an amplifier and shunt in this location 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 can be made with a simple ground referenced

op amp. The AD8417-2 measures current in both directions as the

H-bridge switches and the motor changes direction. The output of

the AD8417-2 is configured in an external referenced bidirectional

mode (see the Bidirectional Operation section).

Figure 32. H-Bridge Motor Control

Figure 33. 3-Phase Motor Control