PIC VPP 13v how much current?

[William At MyBlueRoom]

Please pick one; (A) No real standards I'm aware of. Or, (B) Everyone has their own standard (grin).

I used a pinout that matches the melabs serial and usb programmers so that I could use my melabs programming adapter board.

You could always use an RJ14 connector for an ICD2 compatible ICSP interface.

BTW, did you happen to notice that a VPP voltage of 12v seems to cover more PIC devices than a VPP voltage of 13v?

I chose mine to match the ICD2 adapter cable & the ICD2 clone on ebay (not a good clone; uses the 16F877A so needs a modded bootloader)

I think 13v is so popular because of the 0.7v drop across a typical VPP transistor. 12.3v VPP, and it even works with the 18F series.

 

[Mike - K8LH]

I chose mine to match the ICD2 adapter cable & the ICD2 clone on ebay (not a good clone; uses the 16F877A so needs a modded bootloader)

I think 13v is so popular because of the 0.7v drop across a typical VPP transistor. 12.3v VPP, and it even works with the 18F series.

Not an issue with MOSFET drivers, but an understandable design consideration (bibolar transistors are much cheaper than P-channel MOSFETs).

 

[Nigel Goodwin]

BTW, did you happen to notice that a VPP voltage of 12v seems to cover more PIC devices than a VPP voltage of 13v?

The reason for the almost universal use of 13V was basically to ensure the devices got switched to programing mode - the spec (back in the old days) called for 12V, but if it was only 11.9V it might not work, far easier to aim for 13V and gain reliability.

 

[phamthaihoa]

Great, that's easy. I can get 1 to 2 ma without effort.

I think your schematic have a problem.

Voltage from pin which you use on MAX232 is 8.6V, you use 2 elec-caps and 2 diodes. Vpp generated by that circuit is about 16V - Its too high.
You can use a regulator such as LM317, (resistor: 1K and 220 on ADJ) to generate 13V.

 

[phamthaihoa]

VPP
VDD
GND
PGD
PGC

Microchip ICD2 is like this ! Other manufacture such as Olimex use this.