APM32F103RBT7-R datasheet(22/78 Pages) GEEHY

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P a g e 21

4.5.3

RTC and backup register

RTC has a set of continuously running counters, which can provide calendar, alarm interrupt

and periodic interrupt functions together with software. Its clock source can be an external

32.768KHz crystal oscillator, an internal 40KHz low-speed RC oscillator or an external

high-speed clock with 128 frequency division. In addition, RTC clock error can be calibrated by

a 512Hz signal.

Backup register of 10 16-bit registers is used to save 20 bytes of user data when VDD is

disabled.

RTC and backup register are powered by VDD when VDD is valid; otherwise, they are powered

by VBAT pin. Reset of system or power reset source and wake-up from standby mode will not

cause reset of RTC and backup register.

4.6

Power supply and power supply management

4.6.1

Power supply scheme

Table6 Power Supply Scheme

Name

Voltage range

Description

VDD

2.0～3.6V

VDD powers IO interface directly, and powers core circuit through voltage

regulator.

VDDA

2.4～3.6V

It is connected to VDD, and supplies power to ADC, reset module, RC oscillator

and PLL analog part. When ADC is used, VDDA is greater than or equal ato 2.4V.

VDDA and VSSA should be connected to VDD and VSS respectively.

VBAT

1.8～3.6V

When VDD is disabled, RTC, external 32KHz oscillator and backup register are

powered automatically.

Note: See Figure 7 Power Supply Scheme for more detailed information about how to connect

the power pins

4.6.2

Voltage regulator

The working mode of MCU can be adjusted through voltage regulator so as to reduce power

consumption. It mainly has three working modes.

Table7 Operating Mode of Voltage Regulator

Name

Description

Main mode (MR)

Provide 1.6 power supply (core, memory and peripheral) in normal power mode.

Low-power mode (LPR)

Provide 1.6V power supply in low-power mode, to save the content of register and SRAM.

Power-down mode

Used in the standby mode of CPU; the voltage regulator stops power supply, and except for the

standby circuit and backup area, all contents of registers and SRAM will be lost.

Note: The voltage regulator is always in working state after reset, and outputs with high impedance in power-down

mode.

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