The design integrates a full set of battery cell protections, including: cell overvoltage, cell undervoltage, two levels of overcurrent discharge, overcurrent charge, discharge short circuit, and overtemperature and undertemperature protections. Furthermore, this design also monitors lots of system-level faults, including: cell open wire, host watch dog, charge and discharge MOSFETs faults, MOSFETs overtemperature, and so on. Some of the protections were tested in a TI lab.

Figure 3-7 Cell Overvoltage Protection

Figure 3-9 Overcurrent Discharge Protection

Figure 3-11 Short-Circuit Discharge Protection

Figure 3-13 Short-Circuit Discharge Protection - MOSFET On

Figure 3-8 Cell Undervoltage Protection

Figure 3-10 Overcurrent Charge Protection

Figure 3-12 Short-Circuit Discharge Protection - MOSFET Off

The short circuit discharge protections are tested with the following processes:

1. Both charge and discharge MOSFET are off with DET floating
2. PACK port shorted together with air switch
3. Turn on both charge and discharge MOSFET on with DET connected

Figure 3-14 3.3-V Short and HWD Protections

When 3.3 V is shorted, the MCU is powered off and both BQ76942 devices detect HWD after some delay. Since TIDA-010247 configures MCU wake up from entering lower power mode (no communication with the BQ76942 to save power) every 5s, observe a range of 5s to 10s delay with 10s HWD delay configurations.

Figure 3-15 120 V On-PACK Port – Bottom AFE Maximum Voltage

Figure 3-16 120 V On-PACK Port – Top AFE Maximum Voltage

The 120-V on PACK port test is carried out with both CHG and DSG MOSFET off with DET floating.