AP32 PLL does not lock

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AP32 PLL does not lock

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etolocka
Contributor I
Hi!

I have a problem with the AP32 using a 32.768 KHz xtal. I´m using the values suggested in DE001 errata (10M, 330K and 15pF). I have oscillations with all pieces, but in several cases (a hig percentage) the PLL does not rise its LOCK flag.

The initialization of the PLL is as follows:

PCTL_BCS=0;
PCTL_PLLON=0;

PCTL=0x02; //P=0, E=2

PMSH=3;
PMSL=0xd1; //N=3d1

PMRS=0x28; //L=40

PMDS=1; //R=1

PBWC_AUTO=1;

PCTL_PLLON=1;

while (!PBWC_LOCK);

PCTL_BCS=1; //System clock = VCO


When I comment the wait for LOCK bit, the 100% of pieces works fine.

Sometimes, the program passes the while loop when I touch the xtal or pin 11 with a finger..

What can I do? Try other values for the osc capacitors?
Not to wait for LOCK bit?

Thankfully,
Ernesto.
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etolocka
Contributor I
Additional info:

I use SDIP pieces with 2L47P mask.

Ernesto.
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rhinoceroshead
Contributor I
I would look into the PLL loop filter.  Are you using the recommended values there?  If you're using the first order filter, you could try the second-order filter instead.
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