Atmega and attiny power requirement to program with ISP mkii

[chipwitch]

I want to make a target board for programming Atmel MPU's but don't know how much power I need to make available.  I'm assuming 500mA is way more than necessary.  I plan on powering the board with a 9v battery, so the less power I waste on heating the lab the better.  I'm guessing peak current draw will be in the 20 to 30mA neighborhood, but haven't been able to confirm that.  I went through the Atmega 328 datasheet, but my current aspirations to be a novice hardly qualifies me to know what half that stuff means. 

[zapta]

I want to make a target board for programming Atmel MPU's but don't know how much power I need to make available.  I'm assuming 500mA is way more than necessary.  I plan on powering the board with a 9v battery, so the less power I waste on heating the lab the better.  I'm guessing peak current draw will be in the 20 to 30mA neighborhood, but haven't been able to confirm that.  I went through the Atmega 328 datasheet, but my current aspirations to be a novice hardly qualifies me to know what half that stuff means. 

Try, measure and add margin?

[FreddyVictor]

I'm guessing peak current draw will be in the 20 to 30mA neighborhood, but haven't been able to confirm that.

yep, thats in the right ballpark - I typically see less than 10mA just for mcu
don't forget that if you want to drive any LED's from your pins (low power ones only!) you'll need a fair bit more than this tho'
I would aim for a 100 or 200mA v-reg if this is a general purpose board

[poorchava]

Use a switch-mode power supply. In most cases this is the most efficient way to power anything, that is not high-precision analo (it's just matter of more caraful design in the latter case).

[Psi]

A good size output cap on your powersupply should take care of any large spikes in current draw during programming.

[chipwitch]

Thanks for all the replies.  I've measured the draw of my Mega 1280 board and it was down around 12mA, idle.  I didn't know if the act of programming might make that spike or not.

As I said, I'm using a 9v battery to power the target board.  I have some LM317 and some 5.1V Zeners to choose from for a voltage regulator.  I know they'll waste a little power, but if it only draws 20mA... a 150 ohm resister in series with the zener will keep the resistor under 1/8 watt.  An auto-shutoff circuit is probably in order.