The BQ7961x-Q1 device is a stackable battery monitor that measures cell voltages and temperature. The device supports 6 to 16 series-connected (6S to 16S) battery cells. It allows up to 3 bus bar connections and measurements using cell sensing input channels or a dedicated bus bar channel maximizing the device flexibility to support various battery module sizes.

Multiple devices can be connected in a daisy chain. Each device has a pair of high (north) and low (south) vertical differential communication ports, requiring only one twisted pair cable. The device supports either capacitive only, capacitive and choke, or transformer isolation. Communication is reclocked on each daisy-chained device, ensuring communication integrity for long distances. An optional RING connection is supported to reverse the daisy chain communication direction in case of cable failure. Each device includes a SPI master configured through the GPIOs.

The device is ASIL-D compliant on voltage and temperature measurements, and communication. The ADCs in the daisy-chained devices can be configured to align the start of cell voltage measurements and all cell voltages can be measured within 128 μs. Each cell sensing channel includes with a post-ADC digital low-pass filter (LPF) for noise reduction as well as providing moving average measurement results. The device has 8 GPIOs, all of which are configurable for NTC thermistor connections or use as general purpose I/O. All 8 GPIOs can be measured within 1.6 ms.

The device supports passive balancing through an internal cell balancing MOSFET (CBFET) for each cell. The balancing function runs autonomously without microcontroller (MCU) interaction. It includes an option to pause and then resume balancing based on a programmable threshold detected by the external thermistor or if the die temperature is too high (greater than 105°C). Once balancing starts, the device tracks the balancing time on each cell. MCU can read out the remaining balancing time at any time.

The device includes a hardware OVUV comparator and an OTUT comparator with user configurable thresholds. These can be used as a second-level protector for cell over- and undervoltage and thermistor over- and undertemperature detections independent of ADC measurements.

The device provides an option to embed fault status information to the communication frame. When a device in the daisy chain detects a fault condition, this information is embedded and travels along the communication response frame to the bottom device which can be configured to trigger an NFAULT pin as an interrupt signal to the system. This provides a way to reduce communication overhead without adding an additional twisted pair cable and isolation for faster fault detection.

The device has SLEEP and SHUTDOWN modes for lower power consumption. All functions work in ACTIVE mode, balancing and hardware comparators for OVUV and OTUT also work in SLEEP mode. While in SHUTDOWN, all active functions are turned off. A HW reset function is available and can be activated by the host MCU. The HW reset provides a POR-like event to the device without actual battery removal. This provides a reliable, low cost, and recoverable option to improve overall system robustness.