AD8210

Data Sheet

Rev. D | Page 14 of 16

APPLICATIONS INFORMATION

The AD8210 is ideal for high-side or low-side current sensing.

Its accuracy and performance benefits applications, such as

3-phase and H-bridge motor control, solenoid control, and

power supply current monitoring.

For solenoid control, two typical circuit configurations are used:

high-side current sense with a low-side switch, and high-side

current sense with a high-side switch.

HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE

SWITCH

In this case, the PWM control switch is ground referenced. An

inductive load (solenoid) is tied to a power supply. A resistive

shunt is placed between the switch and the load (see Figure 33).

An advantage of placing the shunt on the high side is that the

entire current, including the recirculation current, can be meas-

ured because the shunt remains in the loop when the switch is

off. In addition, diagnostics can be enhanced because short circuits

to ground can be detected with the shunt on the high side.

INDUCTIVE

LOAD

CLAMP

DIODE

BATTERY

SHUNT

SWITCH

NC = NO CONNECT

5V

+IN

OUT

–IN

GND

NC

AD8210

0.1µF

Figure 33. Low-Side Switch

In this circuit configuration, when the switch is closed, the

common-mode voltage moves down to the negative rail. When

the switch is opened, the voltage reversal across the inductive

load causes the common-mode voltage to be held one diode

drop above the battery by the clamp diode.

HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE

SWITCH

This configuration minimizes the possibility of unexpected

solenoid activation and excessive corrosion (see Figure 34). In

this case, both the switch and the shunt are on the high side.

When the switch is off, the battery is removed from the load,

which prevents damage from potential short circuits to ground,

while still allowing the recirculation current to be measured and

diagnostics to be preformed. Removing the power supply from

the load for the majority of the time minimizes the corrosive

effects that could be caused by the differential voltage between

the load and ground.

INDUCTIVE

LOAD

CLAMP

DIODE

BATTERY

SHUNT

SWITCH

NC = NO CONNECT

5V

+IN

OUT

–IN

GND

NC

AD8210

0.1µF

Figure 34. High-Side Switch

Using a high-side switch connects the battery voltage to the

load when the switch is closed. This causes the common-mode

voltage to increase to the battery voltage. In this case, when the

switch is opened, the voltage reversal across the inductive load

causes the common-mode voltage to be held one diode drop

below ground by the clamp diode.

H-BRIDGE MOTOR CONTROL

Another typical application for the AD8210 is as part of the

control loop in H-bridge motor control. In this case, the AD8210

is placed in the middle of the H-bridge (see Figure 35) so that it

can accurately measure current in both directions by using the

shunt available at the motor. This configuration is beneficial for

measuring the recirculation current to further enhance the

control loop diagnostics.

SHUNT

2.5V

5V

CONTROLLER

NC = NO CONNECT

MOTOR

5V

+IN

OUT

–IN

GND

NC

AD8210

0.1µF

Figure 35. Motor Control Application

The AD8210 measures current in both directions as the H-bridge

switches and the motor changes direction. The output of the

AD8210 is configured in an external reference bidirectional

mode (see the Modes of Operation section).