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Inconsistencies HRM vs. EvalBoard

Question asked by enpa on Oct 6, 2014
Latest reply on Oct 6, 2014 by LiamR

Hello and sorry for bothering you again.

 

I have found two incosistencies between documentation and evaluation board.

Since I am designing my own board I'd like to understand the matter.

 

HFXTAL:

The datasheet states that 12 pF < Cext1 = Cext2 < 18 pF, with a typical value of 15 pF.

The evaluation board uses two 24 pF capacitors. My assumption is that the value in the datasheet is the total loading. The equivalent load of the evalboard is indeed 12 pF + some stray capacitance, which fits the values of the datasheet. I would like to get my thoughts confirmed or corrected

 

VCCM_DIG decoupling:

Page 469 of Rev. A of UG-587 states that VCCM_DIG has to be decoupled with 4.7 uF to DGND. In the evalboard the capacitor has (according to the schematic) a capacity of just 100 nF. Which value is correct?

 

Regards,

Enrico

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