AN2476 datasheet(5/49 Pages) STMICROELECTRONICS

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AN2476

Power supply and clocks

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1.3

Power supply schemes

1.3.1

Power scheme 1: single external 3.3V power source

In this configuration, the internal voltage regulators are switched on by forcing the

VREG_DIS pin to low level. The VCORE supply required for the kernel logic and the VBACKUP

supply required for the backup circuitry are generated internally by the Main Voltage

Regulator or the Low Power Voltage Regulator (depending on the selected low power

mode). This scheme has the advantage of requiring only one power source. Refer to

Figure 1 on page 5.

At power-up and during NORMAL mode (all operating modes except STOP and STANDBY

Modes):

●

The Main Voltage Regulator powers both VCORE supply required for the kernel logic

and the VBACKUP supply required for the backup circuitry.

●

The Low Power Regulator is not used

Figure 1.

Power supply scheme 1 (single 3.3V supply VREGDIS=0) in NORMAL

mode

3.3V

MAIN

VOLTAGE

GP I/Os

OUT

ADC

ADCIN

KERNEL LOGIC

BACKUP

V18_BKP

(CPU &

DIGITAL &

+/-0.3V

VIO=3.3V

VDD_ADC

VSS_ADC

PLL

3.3V

VSS_PLL

VSS_IO

VDD_IO

V18REG

VDD_PLL

VSS18

VSS_BKP

OSC32K, RTC

REGULATOR

MEMORIES)

CIRCUITRY

WAKEUP LOGIC,

VREG_DIS

BACKUP REGISTERS)

I/O LOGIC

IN STANDBY MODE THIS BLOCK IS KEPT POWERED ON

NORMAL

POWER

SWITCH

MODE

V18

10µF

33nF

1µF

LOW POWER

VOLTAGE

REGULATOR

VBACKUP

VCORE

V18

VLPVREG ~1.4V

VMVREG = 1.8V

VSS18

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