BQ76925RGER

The Bq76925 is a host-controlled analog front-end (AFE) and is part of a complete battery pack monitoring, balancing, and protection system. This system is suitable for 3, 4, 5, or 6 series-connected lithium-ion and lithium-polymer batteries. The bq76925 device can easily monitor each cell voltage, battery pack current, and temperature through a host controller. The host can use this information to determine unsafe or faulty operating conditions, such as overvoltage, undervoltage, overheating, overcurrent, cell charge imbalance, state of charge, and state of health. The cell input voltage is output after level conversion, multiplexing, and scaling for measurement by the host ADC. A dedicated pin provides a calibrated low-drift reference voltage for accurate measurement. The voltage across the external sense resistor is amplified and output to the host ADC for charge and discharge current measurement. Two gain settings allow the device to be used with a variety of sense resistor values to operate under various battery pack currents. To enable the host to perform temperature measurement, the AFE provides a separate output pin to bias the external thermistor network. This output can be turned on/off under the control of the host to minimize power consumption. The bq76925 device includes a comparator with a dynamically selectable threshold for monitoring current. The comparator result is driven through an open-drain output to alert the host when the threshold is exceeded. This feature can be used to wake up the host after connecting a load or to report potential fault conditions to the host. The bq76925 device integrates cell balancing FETs that are fully controlled by the host. The balancing current is set through an external resistor and can be set up to 50 mA. These same FETs can be used in conjunction with the cell voltage measurement results to detect an open circuit on the cell detection line. The host communicates with the AFE through the I²C interface. Packet CRC can be optionally used to ensure communication robustness. The device can be placed in a low-current sleep mode through the I²C interface and can be woken up by pulling up the ALERT pin.

Applications

• Li-ion battery pack primary protection
• Cordless power tools
• Light electric vehicles (e-bikes and electric scooters, etc.)
• Uninterruptible Power Supply (UPS) systems
• Medical equipment
• Portable test equipment

Key features

• Analog interface for host cell voltage measurement
• Cell input multiplexer, level translator, and scaler
• Calibrated 1.5V/3.0V low-drift reference voltage for accurate ADC conversion
• Analog interface for host current measurement
• Variable-gain current sense amplifier, compatible with 1mΩ sense resistor
• Switchable thermistor bias output for host temperature measurement
• Overcurrent comparator with dynamically adjustable threshold — reports potential overcurrent faults to host
• Wakes host upon load connection
• Integrated cell balancing FET
• Individual host-controlled balancing current of 50mA per cell
• Cell sense wire open-circuit detection support
• Integrated 3.3V regulator for powering microcontroller or LED
• I²C interface for host communication
• Optional packet CRC for robust communication
• Supply voltage range: 4.2V to 26.4V
• Low power consumption: 40μA typical in normal mode, 1.5μA maximum in sleep mode
• Available in 20-pin HTSSOP or 24-pin VQFN package