LiPo: Simple charger

2013/7/1

this simple charger suitable integrated to some low power device, like dummy load, crystal checker.  

The schematic:

Note:

*charge voltage is  4.15*N+3

* 500R resistor need to be change to suitable value for allow 20mA current pass through the power transistor, or it might not be reach to ~ 350mA charge current, and constant charge period stop early.  if battery voltage is Vbat (4.15xN), then

     R ~= (3v-1.8v(led drop))/0.015

*6.8K need change to  （4.2*N/2.5）*10-10