STM32L4 Bypass Oscillator

[Aaronium]

Hello,

I am designing a circuit that needs a HSE and a LSE oscillator for USB and RTC respectively, and need to solder it by hand. Would a bypass oscillators in a SOT23-5 package (i.e. the SiT2024BA-S2-33E-8.000000G

and the SIT1630AE-S6-DCC-32.768G) work? The RTC does not need to be especially accurate.

Also, if the 32.768 kHz bypass oscillator was powered by the same backup battery as the STM32 would the RTC still work in VBAT mode?

Thank you in advance!

[waclawek.jan]

> Would bypass oscillators in a SOT23-5 package (i.e. the SiT2024BA-S2-33E-8.000000G

> and the SIT1630AE-S6-DCC-32.768G) work?

Yes, if you set RCC_CR.HSEBYP and RCC_BDCR.LSEBYP.

> Also, if the 32.768 kHz bypass oscillator was powered by the same backup battery as the STM32 would the RTC still work in VBAT mode?

Yes.

You can test your setup using a Nucleo-64 board, with a bit of playing around with jumpers/solder bridges (most Nucleo-64 have the LSE crystal populated, but through 0R resistors which can be disconnected). The L4 DISCO would make a nice test vehicle for this purpose, but is unfortunately discontinued.

JW