USB Programmers

This is a question out of curiosity;

There are pic programmers on the market which can operate from USB power. How is this done? The standard USB interface provides 5 volt power alone. If so, where does the 12 or 13 volts come from to allow a flash pic to enter the programming mode?

Also, in reading the programming specs for flash pics F6xx it is stated that programming high voltage is internally generated. How is this posssible, and if so is it also the case for all other flash pics?

Anybody?

Dick

IMO, those programmer use LVP(low voltage programming) or there's an internal circuit to shift-up the voltage.

DI:

Boost converters are dime a dozen these days - especially considering the 13volt supply does not require any large currents. Boosting 5 volts to 15volts (voltage tripling) can be done using a 555 timer and a few diodes and capacitors.

If these USB programmers are meant for most PIC devices, Low Voltage Programming is not always recommended!

-warrier

I am using a PIC16F876 in conjunction with a CP2101 chip that cost $5.00 from digikey. This chip converts to serial data coming from the PIC to USB serial. I power the PIC from the USB as well. However, not being gifted in electronics, I use a max734 to boost the voltage from 5V to 12V and then take down to a nice steady 5V with a 78L05. The USB 5V power supply flucutates too much and since I am using an AD converter I find it easier to do it this way. The CP2101 is a tiny chip but using solder paste and an oven does the job quite well.