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PSoC 5, 3 & 1

Anonymous
Not applicable

I'm developing a USB-CAN bridge using the PSoC5LP. I can see from http://www.cypress.com/?app=forum&id=2233&rID=87297 and also from http://www.cypress.com/?id=4&rID=58952 that the PSoC5LP does not require an external crystal for USB communications, unlike the PSoC5.

   

 

   

The TRM states that when using USB with the 5LP the IMO clock frequency spec is +/- 0.25%. This is up from the (best case) +/- 1% for IMO at 3MHz and +/- 4% at 24MHz when not using USB.

   

 

   

My question is whether the +/- 0.25% frequency accuracy is good enough for reliable CAN communications, or if I still require an external crystal to reliably communicate with CAN. 

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ETRO_SSN583
Esteemed Contributor

This might help in clock calulations -

   

 

   

    

   

          http://cache.freescale.com/files/microcontrollers/doc/app_note/AN1798.pdf

   

 

   

Regards, Dana.

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ETRO_SSN583
Esteemed Contributor

This might help in clock calulations -

   

 

   

    

   

          http://cache.freescale.com/files/microcontrollers/doc/app_note/AN1798.pdf

   

 

   

Regards, Dana.

View solution in original post

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Anonymous
Not applicable

Thank you, Dana, that is really good general CAN advice. I think that the takeaway from that is that with a +/- 0.25% IMO accuracy we will not have an issue even at 1Mbaud on CAN.

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