SLUSA91C October   2010  – October 2015

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration 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: Supply Current
    6. 6.6  Power-On Reset (POR)
    7. 6.7  Wake From Sleep
    8. 6.8  RBI RAM Backup
    9. 6.9  3.3-V Regulator
    10. 6.10 2.5-V Regulator
    11. 6.11 PRES, SMBD, SMBC
    12. 6.12 CHG, DSG FET Drive
    13. 6.13 PCHG FET Drive
    14. 6.14 FUSE
    15. 6.15 Coulomb Counter
    16. 6.16 VC1, VC2, VC3, VC4
    17. 6.17 TS1, TS2
    18. 6.18 Internal Temperature Sensor
    19. 6.19 Internal Thermal Shutdown
    20. 6.20 High-Frequency Oscillator
    21. 6.21 Low-Frequency Oscillator
    22. 6.22 Internal Voltage Reference
    23. 6.23 Flash
    24. 6.24 OCD Current Protection
    25. 6.25 SCD1 Current Protection
    26. 6.26 SCD2 Current Protection
    27. 6.27 SCC Current Protection
    28. 6.28 SBS Timing Requirements
    29. 6.29 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Battery Parameter Measurements
      1. 7.1.1 Charge and Discharge Counting
      2. 7.1.2 Voltage
      3. 7.1.3 Current
      4. 7.1.4 Auto Calibration
      5. 7.1.5 Temperature
      6. 7.1.6 Communications
        1. 7.1.6.1 SMBus On and Off State
        2. 7.1.6.2 SBS Commands
  8. 8 Detailed Description
    1. 8.1 Overview
      1. 8.1.1 Configuration
        1. 8.1.1.1 Oscillator Function
        2. 8.1.1.2 System Present Operation
        3. 8.1.1.3 2-, 3-, or 4-Cell Configuration
        4. 8.1.1.4 Cell Balancing
          1. 8.1.1.4.1 Internal Cell Balancing
          2. 8.1.1.4.2 External Cell Balancing
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Primary (1st Level) Safety Features
      2. 8.3.2 Secondary (2nd Level) Safety Features
      3. 8.3.3 Charge Control Features
      4. 8.3.4 Gas Gauging
      5. 8.3.5 Lifetime Data Logging Features
      6. 8.3.6 Authentication
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 High-Current Path
          1. 9.2.2.1.1 Protection FETs
          2. 9.2.2.1.2 Chemical Fuse
          3. 9.2.2.1.3 Lithium-Ion Cell Connections
          4. 9.2.2.1.4 Sense Resistor
          5. 9.2.2.1.5 ESD Mitigation
        2. 9.2.2.2 Gas Gauge Circuit
          1. 9.2.2.2.1 Differential Low-Pass Filter
          2. 9.2.2.2.2 Power Supply Decoupling and RBI
          3. 9.2.2.2.3 System Present
          4. 9.2.2.2.4 SMBus Communication
          5. 9.2.2.2.5 FUSE Circuitry
          6. 9.2.2.2.6 PFIN Detection
        3. 9.2.2.3 Secondary-Current Protection
          1. 9.2.2.3.1 Cell and Battery Inputs
          2. 9.2.2.3.2 External Cell Balancing
          3. 9.2.2.3.3 PACK and FET Control
          4. 9.2.2.3.4 Regulator Output
          5. 9.2.2.3.5 Temperature Output
        4. 9.2.2.4 Secondary-Overvoltage Protection
          1. 9.2.2.4.1 Cell Inputs
          2. 9.2.2.4.2 Time-Delay Capacitor
      3. 9.2.3 Application Curves
    3. 9.3 System Example
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8 Detailed Description

8.1 Overview

The bq3055 device measures the voltage, temperature, and current to determine battery capacity and state-of-charge (SOC). The bq3050 monitors charge and discharge activity by sensing the voltage across a small value resistor (5 mΩ to 20 mΩ, typical) between the SRP and SRN pins and in series with the battery. By integrating charge passing through the battery, the battery’s SOC is adjusted during battery charge or discharge. Measurements of OCV and charge integration determine chemical SOC.

The Qmax values are taken from a cell manufacturers' data sheet multiplied by the number of parallel cells, and is also used for the value in Design Capacity. It uses the OCV and Qmax value to determine StateOfCharge() on battery insertion, device reset, or on command. The FullChargeCapacity() is reported as the learned capacity available from full charge until Voltage() reaches the EDV0 threshold. As Voltage() falls below the Shutdown Voltage for Shutdown Time and has been out of SHUTDOWN mode for at least Shutdown Time, the PF Flags1 () [VSHUT] bit is set. For additional details, see bq3055 Technical Reference Manual (SLUU440).

Fuel gauging is derived from the Compensated End of Discharge Voltage (CEDV) method, which uses a mathematical model to correlate remaining state of charge (RSOC) and voltage near to the end of discharge state. This requires a full-discharge cycle for a single-point FCC update. The implementation models cell voltage (OCV) as a function of battery SOC, temperature, and current. The impedance is also a function of SOC and temperature, which can be satisfied by using seven parameters: EMF, C0, R0, T0, R1, TC, and C1.

8.1.1 Configuration

8.1.1.1 Oscillator Function

The bq3055 fully integrates the system oscillators and does not require any external components to support this feature.

8.1.1.2 System Present Operation

The bq3055 checks the PRES pin periodically (1 s). If PRES input is pulled to ground by the external system, the bq3055 detects this as system present.

8.1.1.3 2-, 3-, or 4-Cell Configuration

In a 2-cell configuration, VC1 is shorted to VC2 and VC3. In a 3-cell configuration, VC1 is shorted to VC2.

8.1.1.4 Cell Balancing

The device supports cell balancing by bypassing the current of each cell during charging or at rest. If the device's internal bypass is used, up to 10 mA can be bypassed and multiple cells can be bypassed at the same time. Higher cell balance current can be achieved by using an external cell balancing circuit. In external cell balancing mode, only one cell at a time can be balanced.

The cell balancing algorithm determines the amount of charge needed to be bypassed to balance the capacity of all cells.

8.1.1.4.1 Internal Cell Balancing

When internal cell balancing is configured, the cell balance current is defined by the external resistor RVC at the VCx input. See Figure 4.

bq3055 int_cell_lus996.gif Figure 4. Internal Cell Balancing with RVC

8.1.1.4.2 External Cell Balancing

When external cell balancing is configured, the cell balance current is defined by RB. See Figure 5. Only one cell at a time can be balanced.

bq3055 ext_cell_lus996.gif Figure 5. External Cell Balancing with RB

8.2 Functional Block Diagram

bq3055 FunctionBD_3055.gif

8.3 Feature Description

8.3.1 Primary (1st Level) Safety Features

The bq3055 supports a wide range of battery and system protection features that can easily be configured. The primary safety features include:

  • Cell Overvoltage and Undervoltage Protection
  • Charge and Discharge Overcurrent
  • Short-Circuit
  • Charge and Discharge Overtemperature
  • AFE Watchdog

8.3.2 Secondary (2nd Level) Safety Features

The secondary safety features of the bq3055 can be used to indicate more serious faults through the FUSE pin. This pin can be used to blow an in-line fuse to permanently disable the battery pack from charging or discharging. The secondary safety protection features include:

  • Safety Overvoltage
  • Safety Overcurrent in Charge and Discharge
  • Safety Overtemperature in Charge and Discharge
  • Charge FET, Discharge FET, and Precharge FET Faults
  • Cell Imbalance Detection
  • Fuse Blow by Secondary Voltage Protection IC
  • AFE Register Integrity Fault (AFE_P)
  • AFE Communication Fault (AFE_C)

8.3.3 Charge Control Features

The bq3055 charge control features include:

  • Supports JEITA temperature ranges. Reports charging voltage and charging current according to the active temperature range
  • Handles more complex charging profiles. Allows for splitting the standard temperature range into two sub-ranges and allows for varying the charging current according to the cell voltage
  • Reports the appropriate charging current needed for constant current charging and the appropriate charging voltage needed for constant voltage charging to a smart charger using SMBus broadcasts
  • Reduce the charge difference of the battery cells in fully charged state of the battery pack gradually using a voltage-based cell balancing algorithm during charging. A voltage threshold can be set up for cell balancing to be active. This prevents fully charged cells from overcharging and causing excessive degradation and also increases the usable pack energy by preventing premature charge termination.
  • Supports precharging and zero-volt charging
  • Supports charge inhibit and charge suspend if battery pack temperature is out of temperature range
  • Reports charging fault and also indicate charge status through charge and discharge alarms

8.3.4 Gas Gauging

The bq3055 uses the CEDV algorithm to measure and calculate the available capacity in battery cells. The bq3055 accumulates a measure of charge and discharge currents and compensates the charge current measurement for the temperature and state-of-charge of the battery. The bq3055 estimates self-discharge of the battery and also adjusts the self-discharge estimation based on temperature. See the bq3055 Technical Reference Manual (SLUU440) for further details.

8.3.5 Lifetime Data Logging Features

The bq3055 offers limited lifetime data logging for the following critical battery parameters:

  • Lifetime Maximum Temperature
  • Lifetime Minimum Temperature
  • Lifetime Maximum Battery Cell Voltage
  • Lifetime Minimum Battery Cell Voltage

8.3.6 Authentication

  • The bq3055 supports authentication by the host using SHA-1.
  • SHA-1 authentication by the gas gauge is required for unsealing and full access.

8.4 Device Functional Modes

The bq3055 supports three power modes to reduce power consumption:

  • In NORMAL Mode, the bq3055 performs measurements, calculations, protection decisions, and data updates in 0.25-s intervals. Between these intervals, the bq3055 is in a reduced power stage.
  • In SLEEP Mode, the bq3055 performs measurements, calculations, protection decisions, and data updates in adjustable time intervals. Between these intervals, the bq3055 is in a reduced power stage. The bq3055 has a wake function that enables exit from Sleep mode when current flow or failure is detected.
  • In SHUTDOWN Mode, the bq3055 is completely disabled.