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PWang.5
PWang.5
Associate II
August 17, 2021
Solved

STM32F429IGT6's RTC Hardware Design

  • August 17, 2021
  • 2 replies
  • 1406 views

Hi Sir,

We want to use STM32F429IGT6's internal RTC, so we connect pin 6 to backup battery, and add a 32.768K crystal to pin8 pin9, Are there any additional details I missed?

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Best answer by Peter BENSCH

The RTC works in the backup domain, so it makes sense to connect a backup battery to pin VBAT, i.e. pin 6 on your LQFP176. But the LSE pins for the 32 kHz crystal are not pins 8/9, but pins 9/10.

You should also read AN2867, which contains a lot of very helpful information on choosing the right crystal (section 4), load capacitors and creating the layout (section 7.2). In the latter, it is particularly advisable to fully understand Fig. 11 (PCB with separated GND plane and guard ring around the oscillator).

Good luck!

Regards

/Peter

2 replies

Peter BENSCH
Peter BENSCHBest answer
ST Technical Moderator
August 17, 2021

The RTC works in the backup domain, so it makes sense to connect a backup battery to pin VBAT, i.e. pin 6 on your LQFP176. But the LSE pins for the 32 kHz crystal are not pins 8/9, but pins 9/10.

You should also read AN2867, which contains a lot of very helpful information on choosing the right crystal (section 4), load capacitors and creating the layout (section 7.2). In the latter, it is particularly advisable to fully understand Fig. 11 (PCB with separated GND plane and guard ring around the oscillator).

Good luck!

Regards

/Peter

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PWang.5
PWang.5Author
Associate II
August 18, 2021

Hi Peter,

Thanks so much, I correct my question, the LSE pins are pin 9/10, I will read AN2867, and thanks again.

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