LPC2478 LCD clock

sivaramakrishna — Wed, 12 Sep 2018 11:09:58 GMT

HI,

I have configured the LPC2478 LCDDCLK clock to 24MHz O/P and observed that the clock is not reaching to full 0VDC on the negative transition.

I have made the following measurements and observe the issue:

1) Configured the DCLK at Pin 150 to 14MHz and observed the sine wave clk with slow rise and fall times.

2) When it is configured to 24MHz clock the clock signal is not reaching to complete 0VDC on the negative transition.

Can you please suggest the root cause and possible trouble shooting techniques on this.Measurement WF are attached for reference.

Thanks ,

Siva Bommaraju

Re: LPC2478 LCD clock

CarlosCasillas — Fri, 14 Sep 2018 20:11:09 GMT

Hi Siva,

If you are using a custom board, you should verify the general design recommendations for clock signals, as it seems to be hardware related (i.e. unbalanced impedances/capacitances).

As complementary information, you could take a look to the following links:

https://www.nxp.com/docs/en/application-note/AN10778.pdf

http://www.onarm.com/forum/20290/

Hope this will be useful for you.
Best regards!
/Carlos
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LPC2478 LCD clock

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