SLUSBK2I October   2013  – March 2022 BQ76920 , BQ76930 , BQ76940

PRODMIX  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
    1. 6.1 Versions
    2. 6.2 BQ76920 Pin Diagram
    3. 6.3 BQ76930 Pin Diagram
    4. 6.4 BQ76940 Pin Diagram
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Subsystems
        1. 8.3.1.1 Measurement Subsystem Overview
          1. 8.3.1.1.1 Data Transfer to the Host Controller
          2. 8.3.1.1.2 14-Bit ADC
            1. 8.3.1.1.2.1 Optional Real-Time Calibration Using the Host Microcontroller
          3. 8.3.1.1.3 16-Bit CC
          4. 8.3.1.1.4 External Thermistor
          5. 8.3.1.1.5 Die Temperature Monitor
          6. 8.3.1.1.6 16-Bit Pack Voltage
          7. 8.3.1.1.7 System Scheduler
        2. 8.3.1.2 Protection Subsystem
          1. 8.3.1.2.1 Integrated Hardware Protections
          2. 8.3.1.2.2 Reduced Test Time
        3. 8.3.1.3 Control Subsystem
          1. 8.3.1.3.1 FET Driving (CHG AND DSG)
            1. 8.3.1.3.1.1 High-Side FET Driving
          2. 8.3.1.3.2 Load Detection
          3. 8.3.1.3.3 Cell Balancing
          4. 8.3.1.3.4 Alert
          5. 8.3.1.3.5 Output LDO
        4. 8.3.1.4 Communications Subsystem
    4. 8.4 Device Functional Modes
      1. 8.4.1 NORMAL Mode
      2. 8.4.2 SHIP Mode
    5. 8.5 Register Maps
      1. 8.5.1 Register Details
      2. 8.5.2 Read-Only Registers
  9. Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Device Timing
      2. 9.1.2 Random Cell Connection
      3. 9.1.3 Power Pin Diodes
      4. 9.1.4 Alert Pin
      5. 9.1.5 Sense Inputs
      6. 9.1.6 TSn Pins
      7. 9.1.7 Unused Pins
      8. 9.1.8 Configuring Alternative Cell Counts
    2. 9.2 Typical Applications
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Step-by-Step Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
    3. 12.3 Related Links
    4. 12.4 Receiving Notification of Documentation Updates
    5. 12.5 Trademarks
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information
14-Bit ADC

Each BQ769x0 device measures cell voltages and temperatures using a 14-bit ADC. This ADC measures all differential cell voltages, thermistors and/or die temperature with a nominal full-scale unsigned range of 0–6.275 V and LSB of 382 µV.

To enable the ADC, the [ADC_EN] bit in the SYS_CTRL1 register must be set. This bit is set automatically whenever the device enters NORMAL mode. When enabled, the ADC ensures that the integrated OV and UV protections are functional.

For each contiguous set of five cells (VC1 to VC5, VC6 to VC10), when no cells in that particular set are being balanced, each cell is measured over a 50-ms decimation window and a complete update is available every 250 ms. In the BQ76930 and BQ76940, every set of five cells above the primary five cells is measured in parallel. The 50-ms decimation greatly assists with removing the aliasing effects present in a noisy motor environment.

When any cells in a contiguous set of 5 cells are being balanced, those affected cells are measured in a reduced 12.5-ms decimation period, to allow the cell balancing to function properly without affecting the integrated OV and UV protections. Since cell balancing is typically only performed during pack charge or idle periods, the shortened decimation periods should not impact accuracy as the system noise during these times is greatly reduced. This reduced decimation period is only applied to sets where one of the cells is being balanced. The following summarizes this for the BQ76920–BQ76940 devices:

  • VC1 to VC5 measurements are each taken in a 50-ms decimation period when all bits in CELLBAL1 register are 0, and a 12.5-ms decimation period when any bits in CELLBAL1 register are 1.
  • VC6 to VC10 measurements are each taken in a 50-ms decimation period when all bits in CELLBAL2 register are 0, and a 12.5-ms decimation period when any bits in CELLBAL2 register are 1.
  • VC11 to VC15 measurements are each taken in a 50-ms decimation period when all bits in CELLBAL3 register are 0, and a 12.5-ms decimation period when any bits in CELLBAL3 register are 1.
  • Total update interval is 250 ms.

Each differential cell input is factory-trimmed for gain or offset, such that the resulting reading through I2C is always consistent from part-to-part and requires no additional calibration or correction factor application.

The ADC is required to be enabled in order for the integrated OV and UV protections to be operating.

The following shows how to convert the 14-bit ADC reading into an analog voltage. Each device is factory calibrated, with a GAIN and OFFSET stored into EEPROM.

The ADC transfer function is a linear equation defined as follows:

Equation 1. V(cell) = GAIN x ADC(cell) + OFFSET

GAIN is stored in units of µV/LSB, while OFFSET is stored in mV units.

Some example cell voltage calculations are provided in the table below. For illustration purposes, the example uses a hypothetical GAIN of 380 µV/LSB (ADCGAIN<4:0> = 0x0F) and OFFSET of 30 mV (ADCOFFSET<7:0> = 0x1E).


14-Bit ADC ResultADC Result in DecimalGAIN (µV/LSB)OFFSET (mV)Cell Voltage (mV)
0x18006144380302365
0x1F107952380303052
Note:

When entering NORMAL mode from SHIP mode, please allow for the following times before reading out initial cell voltage data:

BQ76920: 250 ms

BQ76930: 400 ms

BQ76940: 800 ms