66AK2G02: load cap value for osc used in SYSOSC_IN?

Sung-IL

Part Number: 66AK2G02

Dear Champs,

Each OSCs used in EVM and ICE EVM have same load CAP(18pF), but different load CAP was used.(22pf in GP EVM, 24pf in ICE EVM).
From datasheet, load CAP can be caluculated Ccl = Cf1xCf2/(Cf1+Cf2) = 11pF in GP EVM and 12pF in ICE EVM. So, I'm confused on this.

Could you please let me know how load cap can be calculated?

Is this also applicable for AUDOSC?

Thanks and Best Regards,

SI.

over 8 years ago

0 Cvetolin Shulev-XID over 8 years ago

TI__Guru 65405 points

Hi SI,

I've forwarded this to the design experts. Their feedback should be posted here.

BR
Tsvetolin Shulev

0 Senthilkumar Srinivasan over 8 years ago

TI__Mastermind 43660 points

Sung-IL,

Please refer below application not to know about load capacitor calculations. What you have mentioned in your post is absolutely correct, the combination of C1 and C2 gives the load capacitor value. The different load capacitance value between GP EVM and ICE EVM might be due to different crystal part number. I would check the crystal parts and update you.

Regards,
Senthil

0 Brian Antheunisse over 8 years ago in reply to Senthilkumar Srinivasan

TI__Expert 5305 points

Can you guys elaborate a little here? My customer has the same question and this did not really get answered.

Those equations in the datasheet were clearly not followed by the EVM designers. Should we just follow the datasheet equations anyway? The problem if we do that is that our Cf1 and Cf2 would equal 36pF each and be out of spec for a crystal with 18pF...

Thanks,

Brian

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66AK2G02: load cap value for osc used in SYSOSC_IN?