Electronics > Microcontrollers

ATMEGA 328P Crystal pf

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zapta:

--- Quote from: sleemanj on May 07, 2014, 05:03:23 am ---If you want to get into specifics though, there is a formula for calculating the capacitor values, given the load capacitance of the crystal from a datasheet.

  CX = 2(CL - Cstray)

CX is the capacitor value you use (assuming you use the same value for both caps),
CL is the load capacitance specified by the crystal
Cstray is stray capacitance inherent in the construction

--- End quote ---

I always assume that Cstray ~ 0,  and CX = CL.  No problem so far but I should spend more time reading the datasheet. ;-)

miguelvp:
based on the previous post to yours, if Cstray is ~0 wouldn't that mean that:

CX = 2*CL ?

But I only read the last two posts :)

dannyf:
In a typical pierce oscillator the two capacitors are in serial and then parallel with the stray capacitance (which is not negligible vs. the load capacitance).

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