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7.4.2 Auxiliary
voltage detector (AVD)
The voltage detector function (AVD) is based on an analog comparison between a V
IT-(AVD)
and V
IT+(AVD)
reference value and the V
DD
main supply voltage (V
AVD
). The V
IT-(AVD)
reference value for falling voltage is lower than the V
IT+(AVD)
reference value for rising
voltage in order to avoid parasitic detection (hysteresis).
The output of the AVD comparator is directly readable by the application software through a
real time status bit (AVDF) in the SICSR register. This bit is read only.
Monitoring the V
DD
main supply
The AVD threshold is selected by the AVD[1:0] bits in the AVDTHCR register.
If the AVD interrupt is enabled, an interrupt is generated when the voltage crosses the
V
IT+(AVD)
or V
IT-(AVD)
threshold (AVDF bit is set).
In the case of a drop in voltage, the AVD interrupt acts as an early warning, allowing
software to shut down safely before the LVD resets the microcontroller. See
.
The interrupt on the rising edge is used to inform the application that the V
DD
warning state
is over
Note:
Make sure the right combination of LVD and AVD thresholds is used as LVD and AVD levels
are not correlated. Refer to
and
for more details.
Figure 17.
Using the AVD to monitor V
DD
V
DD
V
IT+(AVD)
V
IT-(AVD)
AVDF bit
0
1
RESET
IF AVDIE bit = 1
V
hyst
AVD INTERRUPT
REQUEST
INTERRUPT Cleared by
V
IT+(LVD)
V
IT-(LVD)
LVD RESET
Early Warning Interrupt
(Power has dropped, MCU not
not yet in reset)
0
1
hardware
INTERRUPT Cleared by
reset
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