ZHCSMR2B December 2020 – December 2021 BQ76942
The FUSE pin on the BQ76942 device can be used to blow a chemical fuse in the presence of a permanent fail (PF), as well as to detect if an external secondary protector in the system has detected a fault and is attempting to blow the fuse itself. The pin is intended to drive the gate of an NFET, which can be combined with the drive from an external secondary protector, as shown in Figure 12-1. When the FUSE pin is not asserted by the BQ76942 device, it remains in a high-impedance state and detects a voltage applied at the pin by a secondary protector. The device can be configured to generate a PF if it detects a high signal at the FUSE pin.
The device can be configured to blow the fuse when a PF occurs. In this case, the device only attempts to blow the fuse if the stack voltage is above a programmed threshold, based on a system configuration with the fuse placed between the top of stack and the high-side protection FETs. If instead the fuse is placed between the FETs and the PACK+ connector, then the device instead bases its decision on the PACK pin voltage (based on configuration setting). This voltage threshold check is disregarded under certain cases, as described in the BQ76942 Technical Reference Manual.