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Michal Dudka
Michal Dudka
Lead
May 10, 2019
Question

STM32H743V (Y revision) VREFBUF factory trim missing ?

  • May 10, 2019
  • 2 replies
  • 794 views

I've turned on VREFBUFF. Datasheet claims that factory trim values should be automaticaly loaded into VREFBUF->CCR. Thru debug i can see that CCR=00000 (no relevant value loaded). And measurments at VREF+ confirm that.

REF 2.5 = 2.431V

REF 2.048 = 1.992V

REF 1.8 = 1.754V

REF 1.5 = 1.462V

VREF+ pin is unloaded and filtered by 1uF+100nF, VDDA at 3.31V.

Is there any way how to find in FLASH factory trimming constants, or VREF wasn't trimmed at all, and looking for them will be waste of time ?

if somebody needs little bit better values than zeros, i've trim my part at:

REF 2.5 = 2.4997 at CCR = 0x1c

REF 2.048 = 2.048 at CCR = 0x1c

REF 1.8 = 1.800V at CCR = 0x1a

REF 1.5 = 1.500V at CCR = 0x1a

Michal Dudka

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2 replies

flyer31
flyer31
Senior
May 20, 2019

Did you try also to compare VREFBUF to VREFINT? (see Datasheet STM32H750 6.3.5 "Embedded reference voltage")?

I hope VREFINT is as exact as specified (1.216V +- ca. 0.04, -40...105°C, max. 70ppm/°C (typ 20), max. 1000ppm/VoltSupply (typ. 10) this is quite ok for my application... ).

Thomas9
Thomas9
Explorer
June 20, 2019

I am also having the issue where the VREFBUF->CCR register is all zero. According to the reference manual a factory calibration value is supposed to be loaded. When setting the reference voltage to 2.5V I measure between 2.415V and 2.45V. I did enable the VREFBUF clock :

 RCC->APB4ENR |= RCC_APB4ENR_VREFEN ;

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