[HH] low battery indicator

[Tom Metro]

FYI, the June 2012 issue of "Circuit Cellar" has an article on the
Renesas RL78[1] (page 22), which is apparently a low power
microcontroller designed specifically for battery operation, with a
supply voltage from 1.6 V to 5.5 V. It has a snooze mode where you can
choose any of several major sections of the CPU (and integrated
peripherals) to turn off.

1. http://www.renesas.com/products/mpumcu/rl78/index.jsp

Interestingly it seems to have the ability to have the ADC continue to
operate while the rest of the CPU is asleep, and wake up the CPU when a
voltage threshold is reached.

However, keeping the ADC running still consumes 0.5 mA.

(The article is part of some "RL78 Green Energy Design Challenge":
http://www.circuitcellar.com/contests/renesasRL78challenge/
Looks like you need to submit a project proposal, and if they like it,
they send you a free dev kit, and you have a chance to win some of the
$17K in prize money.)

 -Tom