about Atmega128a and crystal load capacitance

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Hello!

I got a question. 

 

I wanna configure an external clock circuit in AVR.

but, To select the crystal,11.0592MHz 

I found load capacitance of crystal. 

 

the load capacitance -> C_Load, capacitance on PCB line(1pF~2pF), and 

internal capacitance in IC -> C_in

 

i found out that i need to match X-tal's C_Load to C_IC + C_stray. 

 

and I put 30pF capacitor for external 

I can count C_load =  (30+Cin)/2+C_strary .

 

I couldn't find the internal capacitance of atmega128  

and what crystal is recommended. 

 

I'm gonna use 11.0592MHz crystal, ATS

WHat  crystal of capacity should i use ??

 

THANK YOU!

 

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Hi! AVR

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It's not super critical. 22-33pF should be adequate. 

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Where is your m128 mounted?  Breadboard or pcb?

you may need smaller caps (18pf) or smaller on a breadboard said the stray cap is higher.

Also you need bypass caps on each power pin pairs, 100nf across both VCC/GND and a Avcc/GND pair.

And while we are talking about m128, most newbies get caught by the m103 fuse that is on by default.

jim

 

 

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