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3v power-up problem with 16LF628

 
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Grailman



Joined: 01 Aug 2005
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3v power-up problem with 16LF628
PostPosted: Mon Aug 29, 2005 10:04 pm     Reply with quote
I have issue with a 16LF628 PIC that will not power up using a 3.1 v suppply. It works fine if I use a 5v supply but when I switch to a 3.1v supply, it just does not power-up. The fuses I set are:

#fuses INTRC_IO, NOLVP, NOWDT, MCLR, BROWNOUT, PUT

where the MCLR pin had a 10K to Vdd and a .1uF cap to gnd. I also tried it without the cap and using the NOMCLR fuse. Neither one worked with the 3.1v supply. If anyone has some pointers about how I should debug this I would sure appreciate some pointers.

Thanks,
Grailman
asmallri



Joined: 12 Aug 2004
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Location: Perth, Australia

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PostPosted: Mon Aug 29, 2005 10:17 pm     Reply with quote
You want nobrownout.
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!
Guest
PostPosted: Tue Aug 30, 2005 11:08 am     Reply with quote
So is there no way to use brown out with a lower voltage?
PCM programmer



Joined: 06 Sep 2003
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PostPosted: Tue Aug 30, 2005 1:17 pm     Reply with quote
Quote:
So is there no way to use brown out with a lower voltage?

Some new PICs allow you to select the Brownout voltage, but not
the 16LF628.

You could use an external Reset Supervisor such as the MCP120 to
do this. The MCP120-270 would work with a PIC running at +3.3v.
It connects to the MCLR pin on the PIC. You need the normal pullup
resistor on MCLR.

Here's a table of all Microchip supervisor chips:
http://www.microchip.com/ParamChartSearch/chart.aspx?mid=11&lang=en&branchID=9008

MCP120 page:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1335&dDocName=en010686

If you're using ICSP to program your PIC, here is a link to AN820
which talks about using ICSP with Reset Supervisors:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011977
Guest
PostPosted: Wed Aug 31, 2005 5:49 am     Reply with quote
Thanks for the great input. This should help out quite a bit!
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