What Voltage needed to Clear Fuses?

soonc · Joined: 03 Dec 2013 Posts: 215

Most older PIC18F run on 3 Volts but require 5Volts to clear fuses.

What parameter in the data sheet defines what voltage level is required to erases fuses.

Some newer PIC18 allow fuses to be erase when the chip is powered with 3Volt.

Is there a parameter in the chip header file that would allow me to see what level is required ?

Example: PIC18F67K22 fuses can be cleared with chip at Vdd 3.3V
PIC18F6722 requires 5 Volts. This adds a complication requiring isolation for parts that only tolerate 3V3 .

Thanks

Ttelmah · Joined: 11 Mar 2010 Posts: 19369

The 6722, does not require 5v.

It requires 4.2v, which is Vmin for the chip.

It is not rated to run below Vmin anyway.....

It is the line in the data sheet that specifies the minimum voltage for a row erase (which is what is required to clear a fuse).

soonc · Joined: 03 Dec 2013 Posts: 215

Ttelmah · Joined: 11 Mar 2010 Posts: 19369

This is very common. A lot of the chips have the data sheet being for the whole family, and you have to look at the electrical characteristics section to verify what version is needed for different voltages. The 67K22 is a better choice, but beware the erratum on the ADC if you are using this.

Best Wishes

temtronic · Posted: Thu May 29, 2014 5:37 pm

Just a 'heads up' that the 18F46K22 can run at 3 volts all day long but at less than 20 MHz.
I don't know if you can use it as I don't know what the '67' has vs the '46'.

There's just too many PICs to remember the specs on !!

The 'devils in the details' as the saying goes.....

sigh

Jay

dyeatman · Joined: 06 Sep 2003 Posts: 1924 Location: Norman, OK

Lately I have been using the 18F27J13 which runs great at 48MHZ in my
3V designs. Not as a big a variety of peripherals but has lots of ROM/RAM.
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