Data Sheet

AD8417

APPLICATIONS INFORMATION

MOTOR CONTROL

3-Phase Motor Control

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

motor applications.

The 250 kHz typical bandwidth of the AD8417 provides

instantaneous 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 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 battery. Refer to Figure 33 for the typical phase current

measurement setup with the AD8417.

H-Bridge Motor Control

Another typical application for the AD8417 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 measures current

in both directions as the H-bridge switches and the motor changes

direction. The output of the AD8417 is configured in an external

referenced bidirectional mode (see the Bidirectional Operation

section).

AD8417

+IN

SHUNT

MOTOR

OUT

–IN

GND

5V

CONTROLLER

NC

5V

2.5V

Figure 32. H-Bridge Motor Control

AD8417

BIDIRECTIONAL CURRENT MEASUREMENT

REJECTION OF HIGH PWM COMMON-MODE VOLTAGE (–2V TO +70V)

AMPLIFICATION

HIGH OUTPUT DRIVE

AD8214

INTERFACE

CIRCUIT

V+

V–

OPTIONAL

DEVICE FOR

OVERCURRENT

PROTECTION AND

FAST (DIRECT)

SHUTDOWN OF

POWER STAGE

AD8417

CONTROLLER

5V

5V

M

Figure 33. 3-Phase Motor Control

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