Post by thread:[EE]: PCB routing across unused pin?

(I always hate putting EE on my subject line. I have an undergrad degree in EE, so I always feel like I should know this) :-) I was wondering if there is any way to route across an unused pin pad on an SMT PIC? If I set up the pin as an output, then it is high-impedence, correct? So, to the circuit it is not there? Thanks! Alex -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu>

> I was wondering if there is any way to route across an unused pin pad on > an SMT PIC? If I set up the pin as an output, then it is > high-impedence, correct? So, to the circuit it is not there? You must set it as an input, not output, and even then the voltage on that pin must not go outside the allowed input for a PIC pin. What about bending that pin up so it doesn't make contact with the pad? Are you doing SMD or through hole? You could just cut the pin off. TTYL -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu>

On Mon, 30 Jun 2003 11:39:46 -0400, you wrote: >> I was wondering if there is any way to route across an unused pin pad on >> an SMT PIC? If I set up the pin as an output, then it is >> high-impedence, correct? So, to the circuit it is not there? > > You must set it as an input, not output, and even then the voltage on that >pin must not go outside the allowed input for a PIC pin. What about bending >that pin up so it doesn't make contact with the pad? Are you doing SMD or >through hole? You could just cut the pin off. TTYL This would be a VERY bad idea for a 'production' product, as it would cause problems when (not if) someone forgets to cut/lift the pin. -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu>

> >> I was wondering if there is any way to route across an unused > pin pad on > >> an SMT PIC? If I set up the pin as an output, then it is > >> high-impedence, correct? So, to the circuit it is not there? > > > > You must set it as an input, not output, and even then > the voltage on that > >pin must not go outside the allowed input for a PIC pin. What > about bending > >that pin up so it doesn't make contact with the pad? Are you doing SMD or > >through hole? You could just cut the pin off. TTYL > > This would be a VERY bad idea for a 'production' product, as it > would cause problems when (not if) > someone forgets to cut/lift the pin. I don't see why, the pin will already be set as input, so unless you are doing something wierd with that trace the "cutting of the pin" is only a backup. -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu>

Except for very good reaason(s), such as a safety or security-based mandate from a customer, e.g., DOD, FAA, FDA, NRC, etc., why would any designer deliberately make a pin unavailable? IMHO it is preferable to keep one's options open. Why burn bridges? Doug Hewett Software engineer, CSDP {Original Message removed}

Herbert Graf wrote: > > > ...You could just cut the pin off. TTYL I am not sure mechanical (and power dissipation) specs would be valid in this case. Mike. -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu>

I'll assume you won't/can't route between pins, but how about switching the functionality of the wire you need to come from the unused pins. Yes, I know you code may not be as clean, but in most cases it should be just as functional, and code is cheap. I've tweaked many a piece of code to help PCB layout. Cheers, -Neil. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads