ZHCSD75D March 2014 – January 2018
A ceramic capacitor at the input to the BAT pin is used to bypass AC voltage ripple to ground, greatly reducing its influence on battery voltage measurements. It proves most effective in applications with load profiles that exhibit high frequency current pulses (that is, cell phones) but is recommended for use in all applications to reduce noise on this sensitive high impedance measurement node.
The series resistor between the battery and the BAT input is used to limit current that could be conducted through the chip-scale package's solder bumps in the event of an accidental short during the board assembly process. The resistor is not likely to survive a sustained short condition (depends on power rating), however, it sacrifices the much cheaper resistor component over suffering damage to the fuel gauge die itself.