BQ76PL455的Fault怎么用？

BQ76PL455的Fault功能是不是用Fault_N引脚来通知MCU是否有Fault信息？如果有Fault信息，再通过UART读取Fault相关寄存器来获得具体的Fault信息？读完后如何reset？

你的理解是对的。

FAULT_N信号可以在UART通讯出问题，或者PL455 ADC等出问题时，还是可以通知MCU在PL455发生了异常，如OV等。

故障消失 ，手动发送命令清楚状态寄存器， 有些寄存器是unlatched， 不用清楚也会消失。

那如果要检测采样线是否断路，这些Fault是不是都没用了？是不是可以用欠压故障来检测采样线断路，欠压故障的值该怎么设置？

BQ76PL455A-Q1有专门的squeeze功能来做断线检测，如下：

A Squeeze function in the device helps to detect open-sense wire (to the monitored cell) conditions. When the
Squeeze function turns on, it places an approximately 5-kΩ resistance across adjacent VSENSE inputs, and
creates an additional voltage drop through the approximately 100-Ω series resistors. This causes the apparent
increase in the voltage applied to the window-comparator blocks immediately above, and below, the inputs that
have the Squeeze resistor applied. Only the comparators can see the increased voltage not the AFE. This in turn
may cause the OV comparator fault to trip, even if the external sense-pin voltage measurement says otherwise,
depending on the OV threshold.