ST10F271 datasheet(104/173 Pages) STMICROELECTRONICS

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Power reduction modes

ST10F271

104/173

Before entering Power Down mode (by executing the instruction PWRDN), bit VREGOFF in

XMISC register must be set.

Note:

Leaving the main voltage regulator active during Power Down may lead to unexpected

behavior (ex: CPU wake-up) and power consumption higher than what specified.

21.2.1

Protected power down mode

This mode is selected when PWDCFG (bit 5) of SYSCON register is cleared. The Protected

Power Down mode is only activated if the NMI pin is pulled low when executing PWRDN

instruction (this means that the PWRD instruction belongs to the NMI software routine). This

mode is only deactivated with an external hardware reset on RSTIN pin.

21.2.2

Interruptible power down mode

This mode is selected when PWDCFG (bit 5) of SYSCON register is set.

The Interruptible Power Down mode is only activated if all the enabled Fast External

Interrupt pins are in their inactive level.

This mode is deactivated with an external reset applied to RSTIN pin or with an interrupt

request applied to one of the Fast External Interrupt pins, or with an interrupt generated by

the Real Time Clock, or with an interrupt generated by the activity on CAN’s and I2C module

interfaces. To allow the internal PLL and clock to stabilize, the RSTIN pin must be held low

according the recommendations described in Chapter 20: System reset on page 78.

An external RC circuit must be connected to RPD pin, as shown in the Figure 36.

Figure 36.

External RC circuitry on RPD pin

To exit Power Down mode with an external interrupt, an EXxIN (x = 7...0) pin has to be

asserted for at least 40ns.

21.3

Stand-by mode

In Stand-by mode, it is possible to turn off the main VDD provided that VSTBY is available

through the dedicated pin of the ST10F271.

To enter Stand-by mode it is mandatory to held the device under reset: once the device is

under reset, the RAM is disabled (see XRAM2EN bit of XPERCON register), and its digital

interface is frozen in order to avoid any kind of data corruption.

A dedicated embedded low-power voltage regulator is implemented to generate the internal

low voltage supply (about 1.65V in Stand-by mode) to bias all those circuits that shall remain

active: the portion of XRAM (8Kbytes), the RTC counters and 32 kHz on-chip oscillator

amplifier.

RPD

VDD

220k

Ω minimum

µF Typical

ST10F271

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