SLUSDW2A November   2021  – February 2022 BQ27Z746

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configurations and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
      1. 6.5.1 Supply Current
      2. 6.5.2 Common Analog (LDO, LFO, HFO, REF1, REF2, I-WAKE)
      3. 6.5.3 Battery Protection (CHG, DSG)
      4. 6.5.4 Cell Sensing Output (BAT_SP, BAT_SN)
      5. 6.5.5 Gauge Measurements (ADC, CC, Temperature)
      6. 6.5.6 Flash Memory
    6. 6.6 Digital I/O: DC Characteristics
    7. 6.7 Digital I/O: Timing Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  BQ27Z746 Processor
      2. 7.3.2  Battery Parameter Measurements
        1. 7.3.2.1 Coulomb Counter (CC) and Digital Filter
        2. 7.3.2.2 ADC Multiplexer
        3. 7.3.2.3 Analog-to-Digital Converter (ADC)
        4. 7.3.2.4 Internal Temperature Sensor
        5. 7.3.2.5 External Temperature Sensor Support
      3. 7.3.3  Power Supply Control
      4. 7.3.4  Bus Communication Interface
      5. 7.3.5  Low Frequency Oscillator
      6. 7.3.6  High Frequency Oscillator
      7. 7.3.7  1.8-V Low Dropout Regulator
      8. 7.3.8  Internal Voltage References
      9. 7.3.9  Overcurrent in Discharge Protection
      10. 7.3.10 Overcurrent in Charge Protection
      11. 7.3.11 Short-Circuit Current in Discharge Protection
      12. 7.3.12 Primary Protection Features
      13. 7.3.13 Battery Sensing
      14. 7.3.14 Gas Gauging
      15. 7.3.15 Zero Volt Charging (ZVCHG)
      16. 7.3.16 Charge Control Features
      17. 7.3.17 Authentication
    4. 7.4 Device Functional Modes
      1. 7.4.1 Lifetime Logging Features
      2. 7.4.2 Configuration
        1. 7.4.2.1 Coulomb Counting
        2. 7.4.2.2 Cell Voltage Measurements
        3. 7.4.2.3 Auto Calibration
        4. 7.4.2.4 Temperature Measurements
  8. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design Requirements (Default)
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Changing Design Parameters
      3. 8.2.3 Calibration Process
      4. 8.2.4 Gauging Data Updates
        1. 8.2.4.1 Application Curve
  9. 9 Power Supply Requirements
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Orderable, and Packaging Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

10.1 Layout Guidelines

  • The quality of the Kelvin connections at the sense resistor is critical. The sense resistor must have a temperature coefficient no greater than 50 ppm to minimize current measurement drift with temperature. Choose the value of the sense resistor to correspond to the available overcurrent and short-circuit ranges of the BQ27Z746 gas gauge. Select the smallest value possible to minimize thermal dissipation and still maintain required measurement accuracy. The value of the sense resistor impacts the differential voltage generated across the BQ27Z746 SRP and SRN nodes during a short circuit. These pins have a differential voltage should not exceed VCC_IN of ± 0.1 V for normal operation. Parallel sense resistors can be used as long as good Kelvin sensing is ensured. The device is designed to support a 1-mΩ to 20-mΩ sense resistor.
  • BAT should be tied directly to the positive connection of the battery with a series 1-kΩ resistor. It should not share a path with the VDD pin and its 10-Ω series resistor.
  • In reference to the gas gauge circuit, the following features require attention for component placement and layout: VDD bypass capacitor, SRN and SRP differential low-pass filter, and I2C communication ESD external protection.
  • The BQ27Z746 gas gauge uses an integrating delta-sigma ADC for current measurements. Add a 100-Ω resistor from the sense resistor to the SRP and SRN inputs of the device. Place a 0.1-μF filter capacitor across the SRP and SRN inputs. Place all filter components as close as possible to the device. Route the traces from the sense resistor as differential pairs to the filter circuit. Adding a ground plane around the filter network can provide additional noise immunity.
  • The BQ27Z746 has an internal LDO that is internally compensated and does not require an external decoupling capacitor.
  • The I2C clock and data pins have integrated high-voltage ESD protection circuits; however, adding a Zener diode and series resistor provides more robust ESD performance. The I2C clock and data lines have an internal pulldown. When the gas gauge senses that both lines are low (such as during removal of the pack), the device performs auto-offset calibration and then goes into SLEEP mode to conserve power.