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RM0367 Rev 7 161/1043

RM0367 Power control (PWR)

172

To further reduce power consumption in Stop mode, the internal voltage regulator can be put

in low-power mode. This is configured by the LPSDSR bit in the PWR_CR register (see

Section 6.4.1). The internal voltage regulator can also be kept in Main mode but the

consumption will be much higher. As a result, it is always implicitly assumed that the

regulator is in low-power mode during Stop mode. The only advantage of keeping the

regulator in Main mode is that the wakeup time from Stop mode is shorter.

If Flash memory programming or an access to the APB domain is ongoing, the Stop mode

entry is delayed until the memory or APB access has completed.

In Stop mode, the following features can be selected by programming individual control bits:

• Independent watchdog (IWDG): the IWDG is started by writing to its Key register or by

hardware option. Once started it cannot be stopped except by a Reset. Refer to

Section 25.3: IWDG functional description in Section 25: Independent watchdog

(IWDG).

• Real-time clock (RTC): this is configured by the RTCEN bit in the RCC_CSR register

(see Section 7.3.21).

• Internal RC oscillator (LSI RC): this is configured by the LSION bit in the RCC_CSR

• External 32.768 kHz oscillator (LSE OSC): this is configured by the LSEON bit in the

RCC_CSR register.

The ADC, DAC and LCD can also consume power in Stop mode, unless they are disabled

before entering it. To disable them, the ADDIS bit in the ADC_CR register must be set to 1

and the ENx bit in the DAC_CR register must be written to 0.

Exiting Stop mode

Refer to Section 6.3.6: Exiting low-power mode and to Table 37 for details on how to exit

Stop mode.

When exiting Stop mode by issuing an interrupt or a wakeup event, the MSI or HSI16 RC

oscillator is selected as system clock depending the bit STOPWUCK in the RCC_CFGR

When the voltage regulator operates in low-power mode, an additional startup delay is

incurred when waking up from Stop mode. By keeping the internal regulator ON during Stop

mode, the consumption is higher although the startup time is reduced.

ST STM32L0x3 User Manual

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