LPCXpresso IDEのトピックCLKOUT less than perfect square wave

CLKOUT less than perfect square wave

lpcware — Wed, 15 Jun 2016 23:10:16 GMT

Content originally posted in LPCWare by tkreyche on Fri Oct 01 18:26:18 MST 2010
I was expecting a better looking square wave from the CLKOUT pin on the LPC1114...see photo for 4 MHz output.

I'm considering using it to drive an external ADC. No problem running it through a clock buffer to clean it up, but still.

Image is from my Tectronix 2445 150 MHz analog scope.

Comments?

Re: CLKOUT less than perfect square wave

lpcware — Wed, 15 Jun 2016 23:10:17 GMT

Content originally posted in LPCWare by Luis Digital on Fri Oct 01 19:53:21 MST 2010

Quote: tkreyche
I was expecting a better looking square wave from the CLKOUT pin...see photo for 4 MHz output. No problem running it through a clock buffer to clean it up, but still.

I'm considering using it to drive an external ADC.

Image is from my Tectronix 2445 150 MHz scope.

Comments?

What is the output of another microcontroller that operates at 4 MHz and 3.3 volts?

I have the same plans, but at 50 MHz, and my ADC is 5.0 volts, so I'll need a buffer. Any recommendations about the buffer is welcome.

Re: CLKOUT less than perfect square wave

lpcware — Wed, 15 Jun 2016 23:10:18 GMT

Content originally posted in LPCWare by Ex-Zero on Fri Oct 01 21:45:05 MST 2010
Perhaps a Schmitt-trigger like:

http://ics.nxp.com/products/lvc/datasheet/74lvc1g14.pdf

Re: CLKOUT less than perfect square wave

lpcware — Wed, 15 Jun 2016 23:10:18 GMT

Content originally posted in LPCWare by Luis Digital on Sat Oct 02 06:15:56 MST 2010
Thanks for the information.

Re: CLKOUT less than perfect square wave

lpcware — Wed, 15 Jun 2016 23:10:19 GMT

Content originally posted in LPCWare by leon_heller on Sat Oct 02 09:29:41 MST 2010
The ringing looks like a measurement artefact. Try using a very short ground connection for the scope probe, attached to a ground close to the pin.