AN2100 datasheet(3/23 Pages) STMICROELECTRONICS

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AN2100

Power supply

3/23

Power supply

1.1

Power supply pins

Figure 1 shows the recommended configuration for the power supply pins:

●

V33 is the 3.3 V main power supply pin. (V33 and V33IO-PLL are internally linked).

●

V18 must be connected to a capacitor of at least 10µF (Tantalum) + 33nF (ceramic) in

order to guarantee the stability of the 1.8 V supply to the core.

●

V18BKP can be used to provide an external 1.8 V supply to the backup block (RTC and

Wake-up logic) when bypassing the internal voltage regulator during STANDBY mode.

Caution:

In STANDBY mode, when using an external 1.8 V on V18BKP, the V33 pin must remain

connected to the 3.3V supply.

Figure 1.

STR71x power supply pins

When not using an external 1.8 V on the V18BKP pin, a 1 µF capacitor must be connected between this pin

and VSSBKP to guarantee on-chip voltage stability.

Connecting an external 1.8 V supply to the V18 pins is not supported.

STR71x

V33

V18

V18BKP

VSS

VSSBKP

VSS18

10µF

33nF

VSSBKP

1µF

VSS

1.8 V

V33IO-PLL

VSSIO-PLL

3.3 V

(Note 1)

optional

VSS18

(Note 2)

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