AN2586 datasheet(6/28 Pages) STMICROELECTRONICS

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Power supplies

AN2586

6/28

Doc ID 13675 Rev 7

Power supplies

1.1

Introduction

The device requires a 2.0 V to 3.6 V operating voltage supply (VDD). An embedded regulator

is used to supply the internal 1.8 V digital power.

The real-time clock (RTC) and backup registers can be powered from the VBAT voltage when

the main VDD supply is powered off.

Figure 1.

Power supply overview

Note:

VDDA and VSSA must be connected to VDD and VSS, respectively.

1.1.1

Independent A/D converter supply and reference voltage

To improve conversion accuracy, the ADC has an independent power supply that can be

filtered separately, and shielded from noise on the PCB.

●

the ADC voltage supply input is available on a separate VDDA pin

●

an isolated supply ground connection is provided on the VSSA pin

When available (depending on package), VREF– must be tied to VSSA.

On 100-pin and 144-pin packages

To ensure a better accuracy on low-voltage inputs, the user can connect a separate external

reference voltage ADC input on VREF+. The voltage on VREF+ may range from 2.4 V to

VDDA.

A/D converter

VDD

VSS

I/O Ring

BKP registers

Temp. sensor

Reset block

Standby circuitry

PLL

(Wakeup logic,

IWDG)

RTC

Voltage regulator

Core

memories'

digital

peripherals

Low voltage detector

(VSSA) VREF–

VDDA domain

VDD domain

1.8 V domain

Backup domain

LSE crystal 32 KHz oscillator

RCC BDCR register

ai14863

(from 2.4 V up to VDDA) VREF+

(VDD) VDDA

(VSS) VSSA

(VDD) VBAT

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