STM32L4 Wrong MSI speed

[Mikhail Lipatov]

Hello! I noticed a speed error on MCU L476 and L433. When setting MSI frequency to 1 MHz, the frequency is 1015.5. (Auto trimered by LSE, LSE enabled and work well) At higher frequencies, the operation is normal. What could be the reason?

[waclawek.jan]

And at lower frequencies?

Have you read out and checked RCC_CR.MSIPLLEN?

Have you checked that LSE is actually running?

JW

[Mikhail Lipatov]

at lower frequencies below 1Mhz MSI get wrong freq, wen i set freq abowe 1 MHz MSI work well.

LSE actually running.

I see this in the care of the frequency when heating and cooling the chip. Indeed, auto-tuning works excellently. When I turn off the MSI, the frequency is very temperature dependent. I would like to work on a frequency selective and below 1 MHz with auto-tuning by MSI.

[Mikhail Lipatov]

Set measured Error %

100000 98306 1,694

200000 196614 1,693

400000 393227 1,69325

800000 786453 1,693375

1000000 1015836 -1,5836

2000000 1998902 0,0549

4000000 3997804 0,0549

8000000 7995608 0,0549

16000000 15991217 0,05489375

24000000 23989823 0,0424041667

[waclawek.jan]

Okay, and with the MSIPLL on, the 1MHz is always off 1.5%, or does it change with temperature?

Can you please have a look at whether RCC_CR.MSIPLLEN stays on?

JW

[Mikhail Lipatov]

1MHz is always off 1.5%, good temperature stability. When I turn off the LSE, the frequency is 998 kHz and is very temperature dependent

RCC_CR.MSIPLLEN

SET_BIT(RCC->CR, RCC_CR_MSIPLLEN) ;

[waclawek.jan]

Sounds like a hardware bug, then...

JW

@Amel NASRI​  , @Viktor POHORELY​ 

[Mikhail Lipatov]

Yes, but in erratasheet not fixed.

I would like to work at low frequencies with quartz stability. But HSE quartz consumes a lot of energy (above 1mA)... It seems that you will have to work at a frequency above 2 MHz