16F628A does not work at 3.3V

IceMetal · Joined: 20 Nov 2008 Posts: 79 Location: white Plains, NY

according to the datasheet
http://www.digikey.com/product-detail/en/PIC16F628A-I%2FP/PIC16F628A-I%2FP-ND/529766
the pic16f628 should work at 3.3V but I can not find the correct set of fuses to getting working at that voltage anything under 4.2V it turns off.
are this the correct fuses?
#FUSES INTRC
#fuses NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP, INTRC_IO

what am I missing?

Gabriel · Joined: 03 Aug 2009 Posts: 1067 Location: Panama

Maybe related to the oscillator speed?
Pager 136 of the datasheet...

.. thats a 100% maybe.
_________________
CCS PCM 5.078 & CCS PCH 5.093

temtronic · Posted: Wed Mar 20, 2013 12:24 pm

From what I read, you'll have to disable the brownout fuse.
"Brown-out Detect Voltage 3.7 4.0 4.3 V"

So my thinking is that since 3.3 < 3.7 , PIC sees a 'brownout' condition and will not operate.

Simple test to confirm....set fuse to NOBROWNOUT... and see what happens.

Also note that 3.3volts is close to 'not working' and the 'L' version should be used.

hth
jay

IceMetal · Joined: 20 Nov 2008 Posts: 79 Location: white Plains, NY

temtronic · Posted: Wed Mar 20, 2013 1:02 pm

some days I amaze myself of the seemingly useless trivia my mind retains....
glad it works.....
prof in college said..better to know which book the information is in, than trying to remember everything....life is too short.

jay

asmboy · Joined: 20 Nov 2007 Posts: 2128 Location: albany ny

DR. J strikes again ;-))

if this is for a commercial release,
you owe it to your customers to use the L , low volt version.

you are in MARGINAL performance land and might check for things like oscillator jitter while in this LV situation compared
with the standard F part.

Mustang1945 · Joined: 07 Jul 2015 Posts: 31 Location: Ecuador

drolleman · Joined: 03 Feb 2011 Posts: 116

The vdd programming voltage must be above 4.5v. Yes it will run at 3.0v +. If you look at table 17-1 it states that the vdd min must be at 4.5v for block erase (D132) to work, and programming. The 628a becomes a pain below 4.5, even the LF version.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

A good upgrade chip for the 16F628 or 16F628a is the 16F1847 (or LF).
It's pin compatible, is designed for low-power (especially the LF version),
has many new features, and costs much less. We did a cost reduction
mod on an old product and used this PIC. It does require ICD3 or Pickit3
or the CCS equivalent programmer. It's supported by MPLAB 8.92
and MPLAB-X and CCS.