CHAPTER 7-2: VBAT Domain(A)
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 271
4. Hibernation Control
This section shows an example of circuit configuration for controlling off-chip power gating through the
microcontroller and an example of the sequence of controlling off-chip gating through the microcontroller.
Overview of Hibernation Control
Hibernation control turns on or off the VCC power supply (for both Always-on Domain and CPU Domain)
by controlling the standby function of the on-board regulator through the VBAT Domain.
To execute hibernation control, supply the VBAT pin with a backup power supply other than the VCC
power supply (system power supply).
Below are the two sources for making the microcontroller return from the hibernation state.
− Alarm interrupt of the RTC
− Wakeup request to the P49/VWAKEUP pin (A request is made at a rising edge.)
To use the alarm interrupt of the RTC to make the microcontroller return from the hibernation state, keep
the 32 kHz oscillation operating even when the VCC power supply is off.
External Connection Examples of FM4 Family
Figure 4-1 Example of External Connection with Input Voltage (VI) of On-board Regulator Lower than 5.5 V
Many on-board regulators enter the standby state when their "STBY" input is L level.
The P48/VREGCTL pin of the VBAT I/O ports is 5 V tolerant and is a pseudo-open drain pin.
Connect the P48/VREGCTL to the "STBY" input of the on-board regulator, and connect a pull-up resistor
to the input voltage (VI) of the on-board regulator
Table 4-1 shows how the on-board regulator operates when the standby signal of the system is buffered
by an open collector buffer, and the buffered standby signal and the P48/VREGCTL are connected by a
wired OR logic circuit.
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