For our battery pack product we are using BQ24250 IC. This IC have EN1, EN2 pins for controlling charge current. If we use this IC in our battery pack and set EN1=1, EN2=0 then ILIM is set by external resistor.
We will set ILIM to 1A and set ICHARGE to 900 mA. The battery pack will have USB input port but only VCC and GND pins are used. (D+ and D- enumeration lines will not be used).
We will select VDPM=4.36V.
1) In this case battery pack can work with universal charger adaptor, with source current more than 1A. So battery pack will get charged with all universal charger.
2) If we connect battery pack to PC. The USB port of PC will source 500 mA of current (since only supply pins are connected and no D+/D- pins connected), in this case ICHARGE is 900 mA, and Isource= 500 mA, so the USB voltage will drop down below 4.3V. If USB voltage is below 4.3V then input current limit falls down to prevent drop in supply voltage (DATASHEET PAGE 27). In such case what will be the range for adjusted current limit value? Will it be below 500 mA? if user used this IC in similar fashion will there be any degrade to IC?