At 11:06 AM 1/19/01 +0100, Jeszs wrote: >Dear piclisters, > >I am using RA4 as output pin to attack a TTL chip. Most of the time this >pin shall be 0 V. > >Since RA4 is open drain output, I need some kind of pull-up circuit. >Frequency is not an issue but could be in the future. >The basic pull-up resistor would be continuously consuming energy and this >is what I see 'ugly' in my design. Are you using 'real' TTL? If so, TTL inputs normally float HI and consume about 1 mA then pulled LO. In other words, the current consumption from a pullup resistor is minor compared to the quiescent current consumed by your TTL logic. If you *are* using real TTL, use a pullup resistor of 4.7K - its gonna cost you 1 mA. If you are using LS TTL, go to 10K. If using HC, go to 100K. dwayne Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 17 years of Engineering Innovation (1984 - 2001) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.