The schematic is uploaded on github.
The chip has 5 pins
Pin 1 CHRG- connected in series to a resistor (1kohm) and a red LED to 5v pin of micro USB connector
Pin 2 is connected to GND
Pin 3 is connected to the Li Ion battery positive terminal.
Pin 4 is connected to the positive +5V pin of the micro USB. A 47uF capacitor is also connected from this pin to GND.
Pin 5 PROG pin is connected to GND through a 5.1kohm resistor. This gives the charger a maximum charging current of 200mA.
According to the datasheet, the CHRG pin will be connected to a low 20uA pulldown once charging completes. I am expecting the LED to turn off, because 20uA shouldn't be enough to make it glow. The open circuit voltage of my Li Ion battery is currently 4.21 volts, which I think has reached the level of charge expected.
Also, my battery has a charge protection circuit built inside it, which prevents over discharge, overcharging and short circuit protection.
My only question is- Why doesnt the LED turn off to denote that charging has completed?