AD8218 查看數據表（PDF） - Analog Devices
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AD8218 Datasheet PDF : 16 Pages
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Data Sheet
APPLICATION NOTES
SUPPLY (VS) CONNECTIONS
The AD8218 includes an internal LDO, which allows the user
to leave the VS pin floating, powering the AD8218 directly from
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 29.
ILOAD
ICHARGE
BATTERY
4V
SHUNT
TO
80V
+IN
–IN
VS
REF
AD8218
ENB
OUT
GND
LOAD
2.5V
Figure 29. Operation with No VS Connection
The AD8218 can also be powered from a separate low impedance
supply at Pin 2 (VS); however, this voltage can only be in the 4 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 30.
ILOAD
ICHARGE
BATTERY
4V
SHUNT
TO
80V
+IN
–IN
CF 5V
VS
REF
AD8218
ENB
OUT
GND
LOAD
2.5V
Figure 30. 5 V Supply Operation
AD8218
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 31.
ILOAD
BATTERY
4V
SHUNT
TO
80V
+IN
–IN
VS
REF
AD8218
ENB
OUT
GND
LOAD
Figure 31. Enabling the Internal 80 mV Reference
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
OUT (V) = OUT (V) = (20 × VIN) + 0.08 V
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.
Rev. B | Page 11 of 16
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