The BQ77915 device is a full-feature stackable primary protector for Li-ion/Li-polymer batteries with a smart cell-balancing algorithm. The device implements a suite of protections that include the following:

• Cell voltage: overvoltage, undervoltage
• Current: overcurrent charge, overcurrent discharge 1 and 2, short circuit discharge
• Temperature: overtemperature and undertemperature in charge and discharge
• PCB: cell open-wire connection
• FET body diode protection

Protection thresholds and delays are factory-programmed and available in a variety of configurations.

The BQ77915 device supports 3-series to 5-series cell configurations. Up to four devices stack to support ≥6-series cell configurations, providing protections up to a 20-series cell configuration. It is possible to support greater than 20-series cell configurations, but with careful consideration of delays.

The device has an ultra-low current HIBERNATE mode for shipping and storage. The device also features a smart cell-balancing algorithm to minimize cell-to-cell imbalance. The BQ77915 has built-in CHG and DSG drivers for low-side N-channel FET protection, which automatically open up the CHG and/or DSG FETs after protection delay time when a fault is detected. A set of CHG/DSG overrides enables disabling the CHG and/or DSG driver externally. Although the host system can use this function to disable the FET control, the main usage of these pins is to channel down the FET control signal from the upper device to the lower device in a cascading configuration in ≥6-series battery packs.