AN1775

1 Power management

5/27

●

V18 can be used to supply an externally regulated 1.8V, but V33 must supply the IOs

●

V18BKP pin can be used to externally supply the backup logic, but V33 must supply the

IOs

●

It is possible to switch-off the MVR and keep LPVR on when the device is in low-power mode

(SLOW, WFI, LPWFI, STOP or STANDBY). The LPVR has a different design from the main VR

and generates a non-stabilized and non-thermally-compensated voltage of approximately 1.6V.

In STANDBY mode the Low Power VR can be switched off when an external regulator provides

In this case we must to keep the 3.3V on pin V33 even if the two regulators are switch off to

keep stable state on the I/Os.

Remark:The PLL is automatically disabled (PLL off) when the MVR is switched off and the

maximum allowed operating frequency is 1 MHz. This is due to the limitation imposed by the

LPVR which is not able to generate sufficient current to operate in run mode.

main regulator.

For more details on the power regulators, refer to the STR71x Reference Manual.