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40 pin PIC Design question

Posted: Tue Mar 10, 2009 8:28 am
by Ron
Hi,

The 40 pin PIC;s have a Vss & Vdd on each side of the PIC. I know it is good practice to place cap across Vss & Vdd as close as possible to the chip.

1) Is it OK to run trace from one Vdd to the other under the chip, same with Vss?

If yes....

2) Do I need 2 caps, 1 per set of Vdd & Vss, or is a single cap fine. I intend to solder cap on bottom side of circuit boards directly under the chip.


Thank you,

Ron

Re: 40 pin PIC Design question

Posted: Tue Mar 10, 2009 12:27 pm
by Benj
Hi Ron

Yyou can choose to connect both of the VDD lines and VSS lines or you can connect only one and use the chip to forward the supply to the other pin.

The best practise is to have the supply rails going to both of the supply pins with caps at both sides of the chips. Soldering the caps directly underneath should work well. You also do not strictly need the caps but 1 is better then 0 and 2 is better then 1. Adding large electrolytics here also helps in very noisy situations.

Re: 40 pin PIC Design question

Posted: Tue Mar 10, 2009 10:01 pm
by Ron
Hi Benj,

Thank you for the help, I really appreciate it.

Any ideas when Flowcode V4 will be out for PIC?

Thanks

Ron

Re: 40 pin PIC Design question

Posted: Wed Mar 11, 2009 9:54 am
by Benj
No problem thanks Ron.

Flowcode V4 is looking like it will be ready for early next month. This has yet to be confimed though so dont take my word on it.