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STM32WL DAC Sample-And-Hold: Internal capacitor?

surumadurum
Associate III

I want to generate a constant, steady voltage as COMP INPM in STOP1 with the DAC (using HAL libs at the moment).

Unfortunately I cannot get a steady signal. The voltage drifts around some seconds, stabilises and starts from the beginning (oddly seems to relate to COMP interrupt, but might be coincidence).

I was wondering whether this is possible without an external capacitor? The manual mentions an internal capacitor and gives formulas to calculate the sample, hold&refresh times, but the specs of the internal cap are nowhere stated.

surumadurum_0-1713209445540.png

Does this mean, sample and hold without external cap only works with disabled buffer and on-chip peripherals selected only?
What would be the correct values for sample,hold&refresh in this scenario?

 

Thanks,

Robert

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