I am working on a pcb that has an on board AVR microcontroller. I am providing a 6 pin programming header for the chip but I want to be able to program the chip without powering the rest of the board. What is the normal setup for something like this? I am thinking I can throw a Zener Diode on the power line to prevent power to the chip from flowing back onto the board and the rest of the components. During normal operation it is just powered from the power plane. Is this a good setup?