Product Specs

Table Of Contents
18 POWER Power supply
Page
81
OFWARN
Figure 15: Power supply supervisor
18.4.1 Power-fail comparator
The power-fail comparator (POF) can provide the CPU with an early warning of impending power failure. It
will not reset the system, but give the CPU time to prepare for an orderly power-down.
The comparator features a hysteresis of V
HYST
, as illustrated in Figure 16: Power-fail comparator (BOR =
Brownout reset) on page 81. The threshold V
POF
is set in register POFCON on page 86. If the POF
is enabled and the supply voltage falls below V
POF
, the POFWARN event will be generated. This event will
also be generated if the supply voltage is already below V
POF
at the time the POF is enabled, or if V
POF
is re-
configured to a level above the supply voltage.
If power-fail warning is enabled and the supply voltage is below V
POF
the power-fail comparator will prevent
the NVMC from performing write operations to the NVM. See NVMC Non-volatile memory controller on
page 29 for more information about the NVMC.
VDD
V
POF
+V
HYST
V
POF
1.7V
t
BOR
Figure 16: Power-fail comparator (BOR = Brownout reset)
To save power, the power-fail comparator is not active in System OFF or in System ON when HFCLK is not
running.
VDD
C
Power on reset
V
BOR
Brownout reset
1.7V
P
Vpof
2.8V
MUX
POFCON
R
...........
MCU
POFWARN
POFWARN