HFXO does not work on nRF52832

Hi,

I cannot start HFXO on nRF52832. I'm using 32MHz crystal TSX-3225 32.0000MF20X-W0(from Mouser) wtih 12pF caps UMK105CG120JV-F(also from Mouser).

Checked with beeper on multimeter, no shorts between pins and between pin and GND.

Looks ok on MCU pin side(QFN package).

This is code

int main(void)
{
    NRF_LOG_INIT(NULL);
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    NRF_CLOCK->TASKS_HFCLKSTART = 1;
    while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);    
And PCB
I'm out of ideas.
Parents Reply
  • The data sheet for that crystal implies 7pF CL although the Mouser listing states 12pF, so 12pF load caps are not correct in either case.

    CL = (CaCb)/(Ca+Cb) + Cstray where Ca=Cb=12pF+Cpin=15pF and Cstray (not pins) say 1pF
         = 8.5pF

    CL = (CaCb)/(Ca+Cb) + Cstray where Ca=Cb=9pF+Cpin=12pF and Cstray (not pins) say 1pF
         = 7pF

    If the Mouser description of 12pF is correct then try 19pF

    CL = (CaCb)/(Ca+Cb) + Cstray where Ca=Cb=19pF+Cpin=22pF and Cstray (not pins) say 1pF
         = 12pF

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