9.2.1.2.1 Negative Output Voltage Protection

Reversely insert the battery pack into the charger output during production or hard shorts on battery to ground will generate negative output voltage on SRP and SRN pin. IC internal electrostatic-discharge (ESD) diodes from GND pin to SRP or SRN pins and two anti-parallel (AP) diodes between SRP and SRN pins can be forward biased and negative current can pass through the ESD diodes and AP diodes when output has negative voltage. Insert two small resistors for SRP and SRN pins to limit the negative current level when output has negative voltage. Suggest resistor value is 10 ohm for SRP pin and 7-8 Ω for SRN pin. After adding small resistors, the suggested pre-charge current is at least 192mA for a 10m ohm current sensing resistor. Another method is using a small diode parallel with output capacitor, when battery connection is reversed the diode turns on and limits the negative voltage level. Using diode protection method without insertion of small resistors into SRP and SRN pin can get the best charging current accuracy.