Hard-wire a small telecom type relay into the circuit where it breaks the connection when the PIC powers down.
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Hard-wire a small telecom type relay into the circuit where it breaks the connection when the PIC powers down.
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pic stays on
Bruce that a good Idea!! Im still wondering why this would happen these things are made to handle this I would think its something internal in the chip they should not bleed into the power rail !!
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The external power feeds through the I/O-pins internal protection diodes.
Look at the port pin block diagrams and you'll see why. You might also try to enable BOR, but I'm not sure that's the best route. Of course, there's always the option of powering your external device from the same power supply. When it's off, it's all off.
Check the attached graphic. With the PIC powered off, and +V applied to the input pin, it goes right through the high-side diode to VDD.
Last edited by Bruce; - 27th August 2010 at 02:25.
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