7805 5v regulator or Zener Diode for pic?

Chet · Post by **Chet** » Wed Nov 14, 2007 4:30 am

I'm struggling with power supply issues and was wondering if
someone has a bullet proof 5v power supply scheme.
Currently I use a 7805 regulator with .1uf tant caps on the input of
the regulator and right next to the pic. This is powered from a 12v
switching power supply. Batteries are not an option.
The problem occurs when power cycle times are less than 30 sec.
I have a 12F675 pic and it gets very upset if I don't wait long enough
to reapply power
Typical config bit settings:

WDT off
PUT ON
BOD off

Post by **Benj** » Wed Nov 14, 2007 10:41 am

Hello Chet

Does the problem still remain if you disable the Power Up Timer (PUT)

Chet · Post by **Chet** » Wed Nov 14, 2007 2:18 pm

I was under the impression that PUT should always be on, but I can
try.
Besides WDT What are the "Standard" settings used by Matrix?

Post by **Benj** » Wed Nov 14, 2007 2:41 pm

Hello Chet

The standard settings for advanced mode are to use the HS crystal oscillator, Enable MCLR and disable everything else.

However Disabling the MCLR and using the Internal Oscillator should be fine too.

The power up timer should only be on if you have a very slow rising voltage curve. With a 7805 and .1uf caps the power up timer should not be required.

Chet · Post by **Chet** » Thu Nov 15, 2007 5:13 am

Thanks, maybe you could add your last comment to the Help file
for Flowcode and Also mention in Flowcourse.