MSP430F149: 32KHz crystal

gaurav gothoskar

Part Number: MSP430F149

Tool/software:

Hello,

I am using a 32KHz crystal (ECS-327-12.5-17x-TR) on the XIN (Pin8) and XOUT(Pin9). I am not connecting any external load capacitors. Can I use the internal load capacitors ? I am experiencing some variable timing issues causing some UART based issues. Can not connecting external capacitors cause these issues? if yes, what nominal values should I use?

Thanks.

5 days ago

0 Diego Abad Sajamin 5 days ago

TI__Expert 8762 points

Hi Gaurav,
I would recommend following the MSP430 Crystal guide for this application.

Best Regards,

Diego Abad

0 gaurav gothoskar 5 days ago in reply to Diego Abad Sajamin

Prodigy 40 points

Thanks Diego. is there a reference design that uses the MSP430F149 or an evaluation board that I can reference.?

0 Diego Abad Sajamin 4 days ago in reply to gaurav gothoskar

TI__Expert 8762 points

Hi gaurav,
There isn't a reference design for this part or an evaluation board. However, it seems you should be able to use the internal load capacitors. The values for them should be 12-pF. You can find more information about them in the TRM's 4.2.2 LFXT1 Oscillator chapter.
Best Regards,
Diego Abad

0 Bruce McKenney 4 days ago

Guru 95385 points

I've used the internal (LFXT) capacitors on an F2 series device (i.e. without external capacitors) with a 12.5pF crystal. I haven't done this on an F1, but I suppose they work the same.

What sort of issues are you seeing? Are you fairly certain the LFXT is oscillating? [It looks like you can output ACLK on P5.6.]

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MSP430F149: 32KHz crystal