Battery Protection Li-Ion 20-Pin TSSOP T/R

The bq76925 Host controlled analog front end (AFE) is part of a complete pack monitoring, balancing and protection system for 3-, 4-, 5-, or 6-series cell Li-Ion and Li-Polymer batteries.The bq76925 allows a Host controller to easily monitor individual cell voltages, pack current and temperature. This information may be used by the Host to determine unsafe or faulty operating conditions such as overvoltage, undervoltage, over-temperature and overcurrent, as well as cell imbalance, state of charge and state of health conditions. Cell input voltages are level-shifted, multiplexed, scaled, and output for measurement by a Host ADC. A low-drift calibrated reference voltage is provided on a dedicated pin to enable accurate measurements. The voltage across an external sense resistor is amplified and output to a Host ADC for both charge and discharge current measurements. Two gain settings enable operation with a variety of sense resistor values over a wide range of pack currents. To enable temperature measurements by the Host, the AFE provides a separate output pin for biasing an external thermistor network.This output can be switched on and off under Host control to minimize power consumption. The bq76925 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 on connection of the load, or to alert the Host to a potential fault condition. The bq76925 integrates cell balancing FETs that are fully controlled by the Host. The balancing current is set by external resistors up to a maximum value of 50 mA. These same FETs may be utilized in conjunction with cell voltage measurements to detect an open wire on a cell sense-line. The Host communicates with the AFE via an I2C interface. A packet CRC may optionally be used to ensure robust operation. The device may be put into a low-current sleep mode via the I2C interface and awakened by pulling up the ALERT pin.

Analog Interface for Host cell Measurement

• Cell Input MUX, Level Shifter, and Scaler
• 1.5-/ 3.0-V Low-Drift, Calibrated Reference Allows
  Accurate Analog to Digital Conversions

Analog Interface for Host Current Measurement

• Variable Gain Current Sense Amplifier Capable of Operation
  with 1-mO Sense Resistor

Switchable Thermistor Bias output for Host Temperature Measurements

Overcurrent Comparator with Dynamically Adjustable Threshold

• Alerts Host to Potential Overcurrent Faults
• May be used to Wake up Host on Load Connect

Integrated Cell Balancing FETs

• Individual Host Control
• 50 mA per-cell Balancing Current

Supports Cell Sense-line Open Wire Detection

Integrated 3.3-V Regulator for Powering Micro-controller and/or LEDs

I²C Interface for Host Communications

• Optional Packet CRC for Robust Operation

Supply Voltage Range From 4.2 to 26.4 V

Low Power Consumption

• 40 µA Typical in Normal Mode
• 1.5 µA Maximum in Sleep Mode

20-pin TSSOP or 24-pin QFN Package