AD8211 Data Sheet
Rev. C | Page 12 of 13
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 25). An advantage of placing the shunt on
the high side is that the entire current, including the recirculation
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.
5V
06824-024
INDUCTIVE
LOAD
CLAMP
DIODE
SHUNT
SWITCH
BATTERY
GND
2
V
IN+
V
IN–
1
5
OUT
V+
3
4
AD8211
123
54
Figure 25. Low-Side Switch
HIGH-SIDE CURRENT SENSING
In this configuration, the shunt resistor is referenced to the
battery. High voltage is 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 AD8211 produces a linear ground referenced,
analog output. An AD8214 can also provide an overcurrent
detection signal in as little as 100 ns. This feature is useful in
high current systems where fast shutdown in overcurrent
conditions is essential.
06824-025
5V
INDUCTIVE
LOAD
CLAMP
DIODE
SHUNT
SWITCH
BATTERY
1234
8765
AD8214
GND NC –INOUT
V
REG
+IN V
S
NC
OVERCURRENT
DETECTION (<100ns)
GND
2
V
IN+
V
IN–
1
5
OUT
V+
3
4
AD8211
123
54
Figure 26. Battery Referenced Shunt Resistor
LOW-SIDE CURRENT SENSING
In systems where low-side current sensing is preferred, the
AD8211 provides an integrated solution with great accuracy.
Ground noise is rejected, CMRR is typically higher than 90 dB,
and output linearity is not compromised, regardless of the
input differential voltage.
06824-026
GND
2
V
IN+
V
IN–
1
5
OUT
V+
3
4
AD8211
5V
INDUCTIVE
LOAD
CLAMP
DIODE
SHUNT
BATTERY
SWITCH
123
54
Figure 27. Ground Referenced Shunt Resistor
