RE: PICKit2 and PIC18F14K50 @ 5V + misc
The problem is unique to this part, and is this:
The PGC and PGD pins of the 18F14K50 are shared with the USB D+ and D- pins. Although the part may be run with a 5 Volt VDD, the maximum voltage that the D+/D- pins can handle is about 3.3V. This is noted in the datasheet and programming spec.
The PICkit 2 (and most other programmers) cannot limit the PGx signal voltages to a range different from VDD, so to prevent damaging a part when a user is unaware of the PGx limitation, the supply voltage is limited.
One way to work around this issue is to
1) Power the 18F14K50 VDD from a 5 volt supply.
2) Do not connect the PICkit 2 VDD pin to the target 5 Volt VDD (leave it unconnected)
- This makes the PICkit 2 think it needs to supply power, so it turns on VDD @ 3.3V
3) The target will now be powered at 5 V, but the PICkit 2 PGx signals will be limited to 3.3V
Another way is to power the target at 5V from a supply and use zeners or other clamping voltage limiters on the PGx pins.