Pic18F452 - Power-up problem

bloues · Joined: 25 Nov 2003 Posts: 3

Hi all

I have a power-up problem with the Pic18F452. Have a look at the design schematic below. The circuit works fine when programmed with the ICD2. When unplugging the ICD, the system starts up correctly and eveything works fine again. But, when shutting down the power and putting it back on again, the system won't start up, then I need to reset it with the ICD2 or a wire from signal_ground to MCLR. I've tried different resistor (R1) values and taken of the cap (C1), but no luck at all.

Can sombebody help me out here?

Thanks
Willie

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martin gordon · Joined: 15 Sep 2003 Posts: 6 Location: Edinburgh

Hi

Your problem could be with the 4K7 and the 10uF =47ms time constant. Reset could take several times this, On power off the cap may not discharge for some time.

Try reducing the cap to 10nF or 1nF

Martin

Guest · Posted: Thu Dec 18, 2003 8:06 am

Hi

The cap (C1) value is actually 10nF and the resistor (R1) is 47k. This doesn't solve my problem.

Thanks for the reply
Willie