AD8215 Data Sheet
Rev. B | Page 12 of 13
APPLICATIONS INFORMATION
HIGH-SIDE CURRENT SENSING 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 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.
07203-027
INDUCTIVE
LOAD
CLAMP
DIODE
SHUNT
SWITCH
BATTERY
54
5V
8 7 6
2 3
5
14
NC V+IN+
IN–
OUT
NCNCGND
AD8215
Figure 28. 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 AD8215 produces a linear ground-referenced
analog output. An AD8214 can also provide an overcurrent
detection signal in as little as 100 ns (see Figure 29). This feature
is useful in high current systems where fast shutdown in over-
current conditions is essential.
07203-028
54
5V
INDUCTIVE
LOAD
CLAMP
DIODE
SHUNT
SWITCH
BATTERY
1234
8765
AD8214
GND NC –INOUT
V
REG
+IN V
S
NC
OVERCURRENT
DETECTION (<100ns)
5 6 7
3 2
8
41
NCV+ IN+
IN–
OUT
NC NC GND
AD8215
Figure 29. Battery-Referenced Shunt Resistor
LOW-SIDE CURRENT SENSING
In systems where low-side current sensing is preferred, the
AD8215 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.
07203-029
INDUCTIVE
LOAD
CLAMP
DIODE
SHUNT
BATTERY
SWITCH
5
4
5V
5 6 7
3 2
8
41
NCV+ IN+
IN–
OUT
NC NC GND
AD8215
Figure 30. Ground-Referenced Shunt Resistor
