thankyou wrote:I'm confused about why the Attiny85 is more popular (on hobby electronics sites) than the picoPower microcontrollers like Attiny43U. Why doesn't everyone want the lowest current consumption, as well as an Attiny with a built in booster to 3V? I'm not sure if there's something I'm missing. I have been using the Attiny85 in my project, and I found out that it was responsible for the majority of the 20 mA current draw. Now I regret not using Attiny43U because I could have had much better battery life.
If the tiny85 is responsible for most of your 20mA draw, then changing to a tiny43U won't fix your problems. The actual AVR core has a max rated consumption of 8mA@8MHz/5V. You don't cross 10mA until about 16MHz@5V. Since you are talking about the tiny43U and its 3V booster, I'm going to assume you are using a 3V supply, in which case the tiny85 core maxes out around 4mA. This assumes that you have followed the "minimizing power consumption" suggestions in section 7.4 of the tiny85 datasheet. As a comparison, the tiny43U core is spec'd at 7mA@8MHz/5V and about 3mA@12MHz/3V.
So lets assume that you are running the chips at their max: 20MHz@5V. Switching chips is going to save you approx 3.75mA or 18.75%. While that is certainly a reasonable savings, it is not going to significantly increase battery life (I interpret significant as 50% increase or more). As I said, you've got other problems.
As a note, the AVR ADC has a conversion complete interrupt than can wake the chip from all but power down mode. In fact, there is a low noise/low power state specifically designed for ADC conversions that stops all the clocks on the chip except the ADC. And, entering this state automatically triggers an ADC conversion so if you are starting a conversion and then spinning of the completion status bit, you are definitely wasting power.