SLUUB65B May   2015  – December 2022

 

  1.   Read This First
    1.     Formatting Conventions Used in This Document
    2.     Related Documentation from Texas Instruments
    3.     Trademarks
  2. 1 Introduction
  3. 2 Basic Measurement System
    1. 2.1 Introduction
    2. 2.2 Current and Coulomb Counting
    3. 2.3 Voltage
    4. 2.4 Temperature
  4. 3 Device Power Modes
    1. 3.1 Introduction
      1. 3.1.1 NORMAL Mode
      2. 3.1.2 SLEEP Mode
      3. 3.1.3 FULLSLEEP Mode
      4. 3.1.4 HIBERNATE Mode
    2. 3.2 Power Control
      1. 3.2.1 Reset Functions
      2. 3.2.2 Wake-Up Comparator
      3. 3.2.3 Flash Updates
  5. 4 Device Configuration Registers
    1. 4.1 Introduction
    2. 4.2 Registers Subclass
      1. 4.2.1 Pack Configuration Register
      2. 4.2.2 Pack Configuration B Register
      3. 4.2.3 Pack Configuration C Register
      4. 4.2.4 Pack Configuration D
  6. 5 System Control Function
    1. 5.1 Introduction
    2. 5.2 SHUTDOWN Mode
    3. 5.3 INTERRUPT Mode
    4. 5.4 Low Capacity
    5. 5.5 Battery Level
    6. 5.6 Safety Conditions
      1. 5.6.1 Overtemperature Fault Conditions During Charge/Discharge
      2. 5.6.2 Tab Disconnect Detection
      3. 5.6.3 ISD Faults
    7. 5.7 Battery Trip Point Interrupt Function
  7. 6 Impedance Track Fuel Gauging
    1. 6.1 Introduction
      1. 6.1.1 System Design Parameters
        1. 6.1.1.1 Design Voltage
        2. 6.1.1.2 Cycle Count
        3. 6.1.1.3 Cycle Count Threshold
        4. 6.1.1.4 Design Capacity
        5. 6.1.1.5 Design Energy
        6. 6.1.1.6 State of Health Load I
        7. 6.1.1.7 Design Energy Scale
        8. 6.1.1.8 System Design Parameters DF
    2. 6.2 Gauge FW Operation Modes
      1. 6.2.1 CHARGE Mode
      2. 6.2.2 RELAXATION Mode
      3. 6.2.3 DISCHARGE Mode
    3. 6.3 Current/Power Profiles
      1. 6.3.1 Load Select
      2. 6.3.2 Thermal Rise Factor
      3. 6.3.3 Thermal Time Constant
    4. 6.4 Qmax Update
      1. 6.4.1 Charge Hysteresis Voltage Shift
    5. 6.5 Fast Qmax Update
    6. 6.6 Resistance Update
    7. 6.7 Fast Resistance Scaling
    8. 6.8 StateOfCharge() Smoothing
      1. 6.8.1 SOC Smoothing in Charge/Discharge
      2. 6.8.2 SOC Smoothing in Relaxation
      3. 6.8.3 SOC Smoothing in Overcharge and Overdischarge Conditions
      4. 6.8.4 StateofCharge() Hold at 99%
      5. 6.8.5 StateofCharge() Hold at 1%
    9. 6.9 Additional Impedance Track Gauging Features
      1. 6.9.1 Trace and Downstream Resistance Compensation
      2. 6.9.2 Imax Calculation
      3. 6.9.3 Predict Outside Temp Time
      4. 6.9.4 State Subclass
        1. 6.9.4.1 Qmax Cell 0
        2. 6.9.4.2 Update Status
      5. 6.9.5 OCV Table Class
        1. 6.9.5.1 OCVa Table Subclass
          1. 6.9.5.1.1 Chemistry Identification
      6. 6.9.6 Ra Table Class
        1. 6.9.6.1 Ra0 Subclass
        2. 6.9.6.2 Ra0x Subclass
  8. 7 Charging Features
    1. 7.1 Introduction
    2. 7.2 Charge Suspend
    3. 7.3 Charge Inhibit
    4. 7.4 JEITA Charging Profile
    5. 7.5 Full Charge Termination Detection
    6. 7.6 Pulse Loads
    7. 7.7 Terminate Voltage Valid Time
    8. 7.8 Charge Termination Subclass
      1. 7.8.1 DOD at EOC Delta Temperature
  9. 8 Lifetime Data Logging Features
    1. 8.1 Introduction
    2. 8.2 Lifetime Data Logging Parameters
    3. 8.3 Feature Access
    4. 8.4 Lifetime Data Subclass, Lifetime Resolution Subclass
      1. 8.4.1 Maximum Temperature, Minimum Temperature, Temperature Resolution
      2. 8.4.2 Maximum Pack Voltage, Minimum Pack Voltage, Voltage Resolution
      3. 8.4.3 Maximum Charge Current, Maximum Discharge Current, Current Resolution
    5. 8.5 Lifetime Resolution Subclass
      1. 8.5.1 Lifetime Update Time
    6. 8.6 Lifetime Temp Samples Subclass
      1. 8.6.1 Flash Write Count
  10. 9 Authentication
    1. 9.1 Introduction
    2. 9.2 Key Programming (Data Flash Key)
    3. 9.3 Key Programming (Secure Memory Key)
    4. 9.4 Executing an Authentication Query
    5. 9.5 Codes Subclass
      1. 9.5.1 Sealed to Unsealed
      2. 9.5.2 Unsealed to Full Access
      3. 9.5.3 Authentication Keys
  11. 10Communications
    1. 10.1 HDQ Single-Pin Serial Interface
    2. 10.2 HDQ Host Interruption Feature
      1. 10.2.1 Low Battery Capacity
      2. 10.2.2 Temperature
    3. 10.3 I2C Interface
      1. 10.3.1 I2C Time Out
      2. 10.3.2 I2C Command Waiting Time
      3. 10.3.3 I2C Clock Stretching
  12. 11Manufacturer Information
    1. 11.1 Manufacturer Information Blocks
    2. 11.2 Manufacturer Information Subclass
      1. 11.2.1 Block A and Block B
  13. 12Manufacturer Data
    1. 12.1 Introduction
    2. 12.2 Manufacturer Data Subclass
      1. 12.2.1 Pack Lot Code
      2. 12.2.2 PCB Lot Code
      3. 12.2.3 Firmware Version
      4. 12.2.4 Hardware Revision
      5. 12.2.5 Cell Revision
      6. 12.2.6 Data Flash Configuration Version
  14. 13Integrity Data or Checksum
    1. 13.1 Introduction
    2. 13.2 Data Flash Checksum
  15. 14Calibration
    1. 14.1 Introduction
    2. 14.2 Current Calibration
    3. 14.3 Offset Calibration
      1. 14.3.1 Coulomb Counter Offset/Board Offset
      2. 14.3.2 Internal/External Temperature Offset
      3. 14.3.3 Pack Voltage Offset
      4. 14.3.4 145
    4. 14.4 Current Measurement Noise Filtering
      1. 14.4.1 Filter
      2. 14.4.2 Deadband
      3. 14.4.3 CC Deadband
      4. 14.4.4 150
  16. 15Data Commands
    1. 15.1 Standard Data Commands
      1. 15.1.1  Control(): 0x00 and 0x01
        1. 15.1.1.1  CONTROL_STATUS: 0x0000
        2. 15.1.1.2  DEVICE_TYPE: 0x0001
        3. 15.1.1.3  FW_VERSION: 0x0002
        4. 15.1.1.4  HW_VERSION: 0x0003
        5. 15.1.1.5  RESET_DATA: 0x0005
        6. 15.1.1.6  PREV_MACWRITE: 0x0007
        7. 15.1.1.7  CHEM_ID: 0x0008
        8. 15.1.1.8  BOARD_OFFSET: 0x0009
        9. 15.1.1.9  CC_OFFSET: 0x000A
        10. 15.1.1.10 DF_VERSION: 0x000C
        11. 15.1.1.11 SET_FULLSLEEP: 0x0010
        12. 15.1.1.12 SET_HIBERNATE: 0x0011
        13. 15.1.1.13 CLEAR_HIBERNATE: 0x0012
        14. 15.1.1.14 SET_SHUTDOWN: 0x0013
        15. 15.1.1.15 CLEAR_SHUTDOWN: 0x0014
        16. 15.1.1.16 SET_HDQINTEN: 0x0015
        17. 15.1.1.17 CLEAR_HDQINTEN: 0x0016
        18. 15.1.1.18 STATIC_CHEM_CHKSUM: 0x0017
        19. 15.1.1.19 ALL_DF_CHKSUM: 0x0018
        20. 15.1.1.20 STATIC_DF_CHKSUM: 0x0019
        21. 15.1.1.21 SYNC_SMOOTH: 0x001E
        22. 15.1.1.22 SEALED: 0x0020
        23. 15.1.1.23 IT ENABLE: 0x0021
        24. 15.1.1.24 IMAX_INT_CLEAR: 0x0023
        25. 15.1.1.25 CAL_ENABLE: 0x002D
        26. 15.1.1.26 RESET: 0x0041
        27. 15.1.1.27 EXIT_CAL: 0x0080
        28. 15.1.1.28 ENTER_CAL: 0x0081
        29. 15.1.1.29 OFFSET_CAL: 0x0082
      2. 15.1.2  AtRate(): 0x02 and 0x03
      3. 15.1.3  UnfilteredSOC(): 0x04 and 0x05
      4. 15.1.4  Temperature(): 0x06 and 0x07
      5. 15.1.5  Voltage(): 0x08 and 0x09
      6. 15.1.6  Flags(): 0x0A and 0x0B
      7. 15.1.7  NomAvailableCapacity(): 0x0C and 0x0D
      8. 15.1.8  FullAvailableCapacity(): 0x0E and 0x0F
      9. 15.1.9  RemainingCapacity(): 0x10 and 0x11
      10. 15.1.10 FullChargeCapacity(): 0x12 and 0x13
      11. 15.1.11 AverageCurrent(): 0x14 and 0x15
      12. 15.1.12 TimeToEmpty(): 0x16 and 0x17
      13. 15.1.13 FilteredFCC(): 0x18 and 0x19
      14. 15.1.14 SafetyStatus(): 0x1A and 0x1B
      15. 15.1.15 UnfilteredFCC(): 0x1C and 0x1D
      16. 15.1.16 Imax(): 0x1E and 0x1F
      17. 15.1.17 UnfilteredRM(): 0x20 and 0x21
      18. 15.1.18 FilteredRM(): 0x22 and 0x23
      19. 15.1.19 BTPSOC1Set(): 0x24 and 0x25
      20. 15.1.20 BTPSOC1Clear(): 0x26 and 0x27
      21. 15.1.21 InternalTemperature(): 0x28 and 0x29
      22. 15.1.22 CycleCount(): 0x2A and 0x2B
      23. 15.1.23 StateOfCharge(): 0x2C and 0x2D
      24. 15.1.24 StateOfHealth(): 0x2E and 0x2F
      25. 15.1.25 ChargingVoltage(): 0x30 and 0x31
      26. 15.1.26 ChargingCurrent(): 0x32 and 0x33
      27. 15.1.27 PassedCharge(): 0x34 and 0x35
      28. 15.1.28 DOD0(): 0x36 and 0x37
      29. 15.1.29 SelfDischargeCurrent(): 0x38 and 0x39
    2. 15.2 Extended Data Commands
      1. 15.2.1  PackConfiguration(): 0x3A and 0x3B
      2. 15.2.2  DesignCapacity(): 0x3C and 0x3D
      3. 15.2.3  DataFlashClass(): 0x3E
      4. 15.2.4  DataFlashBlock(): 0x3F
      5. 15.2.5  BlockData(): 0x40 Through 0x5F
      6. 15.2.6  BlockDataCheckSum(): 0x60
      7. 15.2.7  BlockDataControl(): 0x61
      8. 15.2.8  DODatEOC(): 0x62 and 0x63
      9. 15.2.9  Qstart(): 0x64 and 0x65
      10. 15.2.10 FastQmax(): 0x66 and 0x67
      11. 15.2.11 Reserved—0x68 to 0x6C
      12. 15.2.12 Reserved—0x6E and 0x6F
      13. 15.2.13 Reserved—0x70 and 0x71
      14. 15.2.14 Reserved—0x72 and 0x73
      15. 15.2.15 AveragePower(): 0x76 and 0x77
      16. 15.2.16 AN_COUNTER: 0x79
      17. 15.2.17 AN_CURRENT_LSB: 0x7A
      18. 15.2.18 AN_CURRENT_MSB: 0x7B
      19. 15.2.19 AN_VCELL_LSB: 0x7C
      20. 15.2.20 AN_VCELL_MSB: 0x7D
      21. 15.2.21 AN_TEMP_LSB: 0x7E
      22. 15.2.22 AN_TEMP_MSB: 0x7F
  17. 16Data Flash Summary
    1. 16.1 Introduction
    2. 16.2 Data Flash Interface
      1. 16.2.1 Accessing the Data Flash
      2. 16.2.2 Access Modes
      3. 16.2.3 Sealing or Unsealing Data Flash
    3. 16.3 Data Flash Summary Tables
  18. 17Factory Calibration
    1. 17.1  General I2C Command Information
    2. 17.2  Calibration
      1. 17.2.1 Method
      2. 17.2.2 Sequence
    3. 17.3  Enter CALIBRATION Mode
    4. 17.4  Exit CALIBRATION Mode
    5. 17.5  CC Offset
    6. 17.6  Board Offset
    7. 17.7  Obtain Raw Calibration Data
    8. 17.8  Current Calibration
    9. 17.9  Voltage Calibration
    10. 17.10 Temperature Calibration
    11. 17.11 Floating Point Conversion
  19. 18Updating the BQ27542-G1 Firmware
    1. 18.1 Data Flash Stream (.DFFS)/BMS Data Flash Stream (.BQFS) Files
    2. 18.2 Write Command
    3. 18.3 Read and Compare Command
    4. 18.4 Wait Command
    5. 18.5 Firmware Updating Flow
    6. 18.6 Debugging BQFS Reader and Programmer
    7. 18.7 Creating a BQFS and DFFS Containing User-Specific DFI
  20. 19Impedance Track Gauge Configuration
    1. 19.1 Introduction
    2. 19.2 Determining ChemID
    3. 19.3 Learning Cycle
    4. 19.4 Common Problems Seen During the Learning Cycle
    5. 19.5 Test Gauge and Optimize
    6. 19.6 Finalize Golden File
    7. 19.7 Program and Test the PCB
  21. 20Revision History

6.1 Introduction

The BQ27542-G1 fuel gauge measures the cell voltage, current, and temperature to determine battery SOC based on outputs from the Impedance Track™ algorithm (see the Theory and Implementation of Impedance Track Battery Fuel-Gauging Algorithm Application Report [SLUA450] for more information). The fuel gauge monitors charge and discharge activity by sensing the voltage across a small-value resistor (5-mΩ to 20-mΩ typical) between the SRN and SRP pins and in series with the cell. By integrating charge passing through the battery, the SOC is accurately adjusted during charge or discharge operation. The total chemical capacity of the battery (Qmax) is found by comparing states of charge before and after applying a discharge that results in charge passed of at least 37% of Design Capacity.

The initial Qmax Cell 0 and Design Capacity are set based on values from the applicable cell manufacturers' data sheet multiplied by the number of parallel cells. When a system load is applied, the impedance of the cell is calculated from the OCV, the measured voltage under load, and the discharge current or power as configured in Load Select. The Load Select parameter can be set to various options such as average discharge current from the last cycle (Avg I Last Run), present average discharge current, 14s-filtered AverageCurrent(), Design Capacity/5 discharge rate, a user-defined discharge rate written to AtRate(), or the value programmed in User Rate-mA. The Load Mode parameter extends this further by supporting the same options with respect to power instead of current.

During battery discharge, the fuel gauge simulates an iterative discharge based on the selected load profile and sums the resulting charge it takes to reach Terminate Voltage, the charge passed since the last OCV measurement, and the starting charge passed that is required to reach the last OCV point to determine FullChargeCapacity(), which is the total capacity that can be extracted from a fully charged battery based on the present load profile and temperature. The predicted capacity left in the battery, or RemainingCapacity(), is simply the summed charge from present SOC to Terminate Voltage as determined by the simulation result. The fuel gauge uses the battery impedance and OCV profiles, Qmax, and present SOC to achieve this accurate prediction.

During battery charge, the fuel gauge coulomb counts up from where the last discharge ended and stores the battery voltage once charge termination is detected (V at Chg Term) to compute the depth-of-discharge (DOD) at end of charge (DOD@EOC). This provides a more accurate 100% SOC reference point for deriving starting charge passed (Qstart) since most systems do not charge the battery to absolutely full. In addition to RemainingCapacity() and FullChargeCapacity(), the fuel gauge also reports uncompensated (that is, <C/20) versions of capacity in NominalAvailableCapacity() and FullAvailableCapacity(), respectively. At relaxation entry (|AverageCurrent()| < Quit Current for Chg Relax Time or Dsg Relax Time, depending on previous state), the fuel gauge waits 60 seconds before beginning to take OCV measurements to check that the battery is in a well-relaxed state (dV/dt < 1 µV/s) and to update the reported SOC every hour (although accumulated charge can result in change to SOC between these updates).