STM32F4 Power scale modes

bl · ‎2013-09-13

Posted on September 13, 2013 at 10:40

Hi Folks

I been looking for information on the power scale modes of the STM32F4 and I've not been able to find any information on them - is there a good doc out there that explans them??

Thanks

CS

#pwr #stm32f4-main-power-regulator

Tesla DeLorean · ‎2013-09-13

Posted on September 13, 2013 at 13:11

Well there's the reference manual and the examples.

You can dynamically change the processor speed which is quite impactful, and also spinning in WFI loops rather than grinding in regular code.

Other modes involve turning off clocks and power, which can be quite difficult to handle, and slow to exit. STANDBY exits via a RESET, so you have to be prepared to catch that case and initialize things appropriately.

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jpeacock2399 · ‎2013-09-13

Posted on September 13, 2013 at 15:50

A simple way to reduce power with minimal impact is to use sleep mode when idle. Sleep mode stops the CPU clock but retains SRAM and peripheral settings, so the CPU recovers quickly from sleep mode. Look at sleep mode and WFI instruction.

If your app is interrupt/event driven then sleep is a cheap power saver. I use it as the idle task in FreeRTOS.

Jack Peacock

waclawek.jan · ‎2013-09-13

Posted on September 13, 2013 at 16:16

If you are looking at how does/do the VOS bit/bits in PWR_CR impact the maximum clock/consumption, RM0090 refers you to the individual datasheets.

For example, for STM32F405/407, from Tab14 and its footnote follows, that setting VOS=0 requires maximum frequency to be 144MHz, and yields around 10% gain in power consumption.

JW