XCAP settings

Assaf Blank

Other Parts Discussed in Thread: MSP430F5437

Dear forum members,

I need a clarification: We are using the MSP430F5437 with a 32Khz crystal (Crystal load capacitance as it appears in the datasheet = 12pF).

Do I need to add external capacitors or can I just set the XCAP settings to XCAP=3 (CL=12pF)?

Thanks in advance,

Assaf

over 14 years ago

0 Jens-Michael Gross over 14 years ago

Guru 227245 points

If you want to add external capacitors, you should use XCAP=0 (there's still 2pF per pin parasitic capacitance = 1pF load).The other XCAP settings enable on-chip capacitors, which are fin in most cases.

It might be necessary to use external caps if you want to add an adjustable capacitor for fine tuning, or if the required load cannot be generated with the internal caps.

0 Assaf Blank over 14 years ago in reply to Jens-Michael Gross

Prodigy 230 points

O.K.

But again, just to clear things to me: If I'm using an external oscillator with a load capacitance of 12pF, then using the XCAP=3 setting will do the job? Or must I use also an additional external capacitor?

0 Jens-Michael Gross over 14 years ago in reply to Assaf Blank

Guru 227245 points

Assaf Blank said:
If I'm using an external oscillator with a load capacitance of 12pF, then using the XCAP=3 setting will do the job?

Yes - in XT1LF mode. For HF crystals, the internal capacitors are unavailable. (an you usually need more than 12pF anyway)

0 Assaf Blank over 14 years ago in reply to Jens-Michael Gross

Prodigy 230 points

Thanks.

We do use in XT1LF mode.

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XCAP settings