ad8218brmz-rl Analog Devices, Inc., ad8218brmz-rl Datasheet - Page 11

• Manufacturer Part Number: ad8218brmz-rl
• Description: Zero Drift, Bidirectional Current Shunt Monitor Ad8218
• Manufacturer: Analog Devices, Inc.

APPLICATION NOTES
SUPPLY (V
The AD8218 includes an internal LDO, which allows the user
to leave the V
the voltage present at Pin 1 (+IN), provided this voltage is in the
4 V to 80 V range. A typical connection for the part in this
configuration is shown in Figure 28.
The AD8218 can also be powered from a separate low impedance
supply at Pin 2 (V
to 5.5 V range. In cases where the high voltage bus is susceptible
to noise, transients, or high voltage fluctuations and a 5 V supply is
available, the AD8218 can be used in the mode depicted in
Figure 29.
BATTERY
BATTERY
C
F
S
S
Figure 28. Operation with No V
) CONNECTIONS
pin floating, powering the AD8218 directly from
5V
S
); however, this voltage can only be in the 4 V
Figure 29. 5 V Supply Operation
I
4V
TO
80V
4V
TO
80V
LOAD
I
LOAD
V
ENB
V
ENB
+IN
+IN
S
S
AD8218
AD8218
SHUNT
SHUNT
GND
GND
OUT
REF
OUT
REF
–IN
–IN
S
I
I
CHARGE
CHARGE
Connection
LOAD
LOAD
2.5V
2.5V
Rev. A | Page 11 of 16
ENABLE PIN (ENB) OPERATION
The AD8218 includes an internal reference that can be enabled
by connecting Pin 3 (ENB) to ground. This mode of operation
is shown in Figure 30.
In this configuration, the internal 80 mV reference is activated,
and the output of the AD8218 is 80 mV when the differential
input voltage is 0 V and the voltage at Pin 7 (REF) is also 0 V. This
internal reference is useful in unidirectional current measurements
where the current being monitored has a very wide range. Setting
the output starting point to 80 mV means that when the load
current through the shunt resistor is 0 A, the output is 80 mV.
This ensures that the output errors due to initial offset and the
output saturation range of the amplifier are overcome. In this
mode, the transfer function of the AD8218 becomes
If Pin 3 is connected to ground, and therefore the internal
reference is enabled, 80 mV must always be added to the
transfer function of the AD8218.
OUT (V) = OUT (V) = (20 × V
BATTERY
Figure 30. Enabling the Internal 80 mV Reference
4V
TO
80V
V
ENB
+IN
S
AD8218
SHUNT
I
GND
LOAD
IN
REF
OUT
–IN
) + 0.08 V
LOAD
AD8218