Hi,
I work on the train during my commute, and I'd like to be able to power my uP development board from my laptop (its a small dev board), so I can do code development and testing.
I thought about using the USB port to provide 5V, and then using a MAX1811 or LTC4053 to charge a 4.2V Li battery, which in turn feeds a LT1308B or MAX1771 boost converter to give 5/9/12V etc. at a few 10s of mA.
Is this a reasonable idea? It shouldn't load the USB port too much - both the MAX & LT Li chargers are designed to run from a USB port, so shouldn't overload it, and the boost converter should give me fairly clean power at whatever voltage I need. I can charge the unit at work from the desk PCs, and therefore the loading on the laptop should be minimal for the hour on the train.
Are there better ways of doing this? Is there a cheap commercial alternative already available? This should end up very small and should cost about USD
15 to 20 when made on a PCB. Alternative chips would be a help too...Thanks for your input,
Mike