AN4080 datasheet(9/35 Pages) STMICROELECTRONICS

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AN4080

Power supplies and reset sources of the STM32F0xx family

1.1.1

Independent analog converter supply

To improve conversion accuracy and to extend the supply flexibility, the analog domain has

an independent power supply which can be separately filtered and shielded from noise on

the PCB.

•

The ADC and DAC voltage supply input is available on a separate VDDA pin.

•

A separated supply ground connection is provided on pin VSSA.

The VDDA supply can be equal to or higher than VDD. This allows VDD to stay low while still

providing the full performance for the analog blocks.

When a single supply is used, VDDA must be externally connected to VDD. It is

recommended to use an external filtering circuit in order to ensure a noise free VDDA.

When VDDA is different from VDD, VDDA must be always higher or equal to VDD. To keep

safe potential difference between VDDA and VDD during power-up/power-down, an external

Schottky diode may be used between VDD and VDDA. Refer to the datasheet for the

maximum allowed difference.

Figure 3. Schottky diode connection

1.1.2

Battery backup

To retain the content of the Backup registers when VDD is turned off, the VBAT pin can be

connected to an optional standby voltage supplied by a battery or another source.

The VBAT pin also powers the RTC unit, allowing the RTC to operate even when the main

digital supply (VDD) is turned off.

The switch to the VBAT supply is controlled either by the POR/PDR circuitry embedded in

the reset block on STM32F0x1/x2 devices, or by the NPOR pin on STM32F0x8 devices.

If no external battery is used in the application, it is recommended to connect VBAT

externally to VDD.

AN4080 数据表(PDF) 9 Page - STMicroelectronics