SOFT POWER MANAGEMENT
The FDC37C93xFR employs soft power
on the button input or on any of the enabled
wakeup events (SPx) causes the nPowerOn
output to go active low which turns on the main
power supply. Even if the power supply is
completely lost (i.e., VTR is not present) the
power supply can still be turned on upon the
return of VTR by an alarm 2 event that has
already passed (if the alarm 2 remember bit is
enabled) or by a VTR power on reset (if the VTR
POR bit is enabled). These bits are described in
the Real Time Clock section.
management to allow the chip to enter low
power mode and to provide a variety of wakeup
events to power up the chip. This technique
allows for software control over powerdown and
wakeup events. In low power mode, the chip
runs off of the trickle voltage, VTR, which is 5
volts at 2mA maximum. In this mode, the chip
is ready to power up from either the power
button or from one of a number of wakeup
events including pressing a key, touching the
mouse or receiving data from one of the UARTs.
The alarm can also be set to power up the
system at a predetermined time to perform one
or more tasks.
The button input can be used to turn off the
power supply after a debounce delay. The
power supply can also be turned off under
software control (via
a
write to register
The implementation of Soft Power Management
is illustrated in Figure 9. A high to low transition
WDT_CTRL with bit 7 set).
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