AD8213

Rev. 0 | Page 12 of 16

APPLICATIONS INFORMATION

HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE

SWITCH

In such load control configurations, the PWM controlled 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 28). An advantage of placing the shunt on

the high side is that the entire current, including the recircu-

lation current, can be measured, because the shunt remains in

the loop when the switch is off. In addition, diagnostics can be

enhanced because shorts to ground can be detected with the

shunt on the high side. In this circuit configuration, when the

switch is closed, the common-mode voltage moves down to

near 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.

–IN2

1

+IN2

2

GND

3

OUT2

4

CF2

5

+IN1

9

V+

8

OUT1

7

CF1

6

AD8213

INDUCTIVE

LOAD

CLAMP

DIODE

SWITCH

SHUNT

BATTERY

INDUCTIVE

LOAD

CLAMP

DIODE

SWITCH

SHUNT

BATTERY

5V

CAP1

CAP2

Figure 28. Low-Side Switch

HIGH-SIDE CURRENT SENSING

In this configuration, the shunt resistor is referenced to the

battery. High voltage will be present at the inputs of the current

sense amplifier. In this mode, the recirculation current is again

measured and shorts to ground can be detected. When the

shunt is battery referenced the AD8213 produces a linear

ground referenced analog output. An AD8214 can also be used

to provide an overcurrent detection signal in as little as 100 ns.

This feature will be useful in high current systems, where fast

shutdown in overcurrent conditions is essential.

–IN2

1

+IN2

2

GND

3

OUT2

4

CF2

5

+IN1

9

V+

8

OUT1

7

CF1

6

AD8213

LOAD

SWITCH

CAP2

SHUNT

1

2

+IN

3

4

NC

8

–IN

7

NC

6

GND

5

OUT

AD8214

OVERCURRENT

DETECTION (<100ns)

LOAD

SWITCH

CAP1

SHUNT

1

2

+IN

3

4

NC

8

–IN

7

NC

6

GND

5

OUT

AD8214

OVERCURRENT

DETECTION (<100ns)

5V

Figure 29. Battery Referenced Shunt Resistor

LOW-SIDE CURRENT SENSING

In systems where low-side current sensing is preferred, the

AD8213 provides an integrated solution with great accuracy.

Ground noise is rejected, CMRR is typical higher than 90 dB, and

output linearity is not compromised, regardless of the input

differential voltage.

–IN2

1

+IN2

2

GND

3

OUT2

4

CF2

5

+IN1

9

V+

8

OUT1

7

CF1

6

AD8213

INDUCTIVE

LOAD

CLAMP

DIODE

SWITCH

SHUNT

BATTERY

INDUCTIVE

LOAD

CLAMP

DIODE

SWITCH

SHUNT

BATTERY

5V

Figure 30. Ground Referenced Shunt Resistor