CHAPTER 7-2: VBAT Domain(A)
246 FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E
1. Overview of VBAT Domain
The power consumed while the RTC is in operation can be reduced by using the VBAT power supply pin,
which provides independent power supply for the RTC (calendar circuit) and the 32 kHz oscillator.
Configuration of Power Supply Domain
This family consists of the following three power supply domains.
CPU Domain
This domain consists of the following circuits.
− CPU
− On-chip Flash memory
− On-chip SRAM*
− Peripheral functions
This domain receives power supply from the VCC power supply pin. The power supply is cut off in deep
standby RTC mode and deep standby stop mode.
*: SRAM0, SRAM1, and SRAM2 are provided and SRAM2 can be set to keep data.
Always-ON Domain
This domain consists of the following circuits.
− On-chip regulator
− Power management circuit
− Port circuit
− Main oscillation circuit and I/O Port
This domain receives power supply from the VCC power supply pin.
The VCC power supply pin receives power from the system power supply (on-board regulator).
VBAT Domain
This domain consists of the following circuits.
− RTC
− 32 kHz oscillation circuit
− Power-on circuit
− Backup registers
− Port circuit
This domain always receives power supply from the VBAT power supply pin.
The VBAT power supply pin receives power from a backup power supply (such as a battery) and the
system power supply.
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