ZHCSD75D March 2014 – January 2018
A protection network composed of resistors and zener diodes is recommended on each of the serial communication inputs to protect the fuel gauge from dangerous ESD transients. The Zener should be selected to break down at a voltage larger than the typical pullup voltage for these lines but less than the internal diode clamp breakdown voltage of the device inputs (~6 V). A zener voltage of 5.6 V is typically recommended. The series resistors are used to limit the current into the Zener diode and prevent component destruction due to thermal strain once it goes into breakdown. 100 Ω is typically recommended for these resistance values.
For HDQ-based designs, a pullup resistor is normally designed in on the battery pack PCB and can be connected to the RC2 input since a 1.8-V pullup voltage is readily available and provided by the fuel gauge.