Help me choose the right components! :) Boost converter, micro, etc.

[cahe]

Hello,

I'm thinking of creating my first more advanced (for me) project. It will be a boost converter for a 18650 battery (2.5V-4.2V) that will boost the voltage to 8v and when the time comes (when liion hits 2.75v) it will lover the boosted voltage to 7v (so a low battery alarm triggers on the device being powered). This solves one problem - the device is not designed to work with li-ion technology, and has higher low battery voltage alarm than ideal. Thus when using LiIon packs the alarm triggers much too early (noticable when charging that battery again. A 3000mAh battery only receives 1800mAh during charging)

This boost converter should have the highest (reasonably speaking) efficiency possible, so this is worthwhile. Right now the low voltage alarm rings at about 7V (so for 2S LiIon pack 3.5V per cell). The device draws about 350mA at 8V. I can configure the packs in 1S2P or 2S1P configuration to gain some efficiency. I'm interested in SMT components. The boost converter should be ideally controlled by a PWM signal, since I'm planning on adding some kind of micro controller (maybe with a screen, buzzer, etc.). The micro could also control the transistion from 8V to 7V.

Thanks in advance for all the suggestions and help!

[cahe]

I'm thinking about http://www.ti.com/product/TPS63070