Analog Front End for 3 to 6 Series Lithium-Ion Cells - BQ76925

BQ76925 (ACTIVE)

Analog Front End for 3 to 6 Series Lithium-Ion Cells

 

Description

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 device allows a Host controller to monitor individual cell voltages, pack current and temperature easily. The Host may use this information to determine unsafe or faulty operating conditions such as overvoltage, under- voltage, overtemperature, overcurrent, 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 dedicated pin provides a low-drift calibrated reference voltage 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 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 on connection of the load, or to alert the Host to a potential fault condition.

The bq76925 device 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 through 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 through the I2C interface and awakened by pulling up the ALERT pin.

Features

  • 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-mΩ Sense Resistor
  • Switchable Thermistor Bias Output for Host Temperature Measurements
  • Overcurrent Comparator With Dynamically Adjustable Threshold
    • Alerts Host to Potential Overcurrent Faults
    • Wakes 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 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 VQFN Package

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Parametrics Compare all products in Battery Monitor, Protection & Authentication Solutions

 
Function
Number of Series Cells (Min)
Number of Series Cells (Max)
Communication Interface
Features
Typical Operating Current (Typ) (uA)
Rating
Vin (Max) (V)
Pin/Package
BQ76925
Monitoring (Analog Front-End)   
3   
6   
I2C   
Analog current sense
Cell Balancing
LDO
Requires separate MCU
Temperature sense
Short-circuit Discharge (SCD)   
40   
Catalog   
26.4   
20TSSOP
24VQFN