JAJSL08H september   2009  – february 2021 BQ24040 , BQ24041 , BQ24045

PRODUCTION DATA  

  1.   1
  2. 特長
  3. アプリケーション
  4. 概要
  5. Revision History
  6. Device Comparison
  7. Pin Configuration and Functions
  8. 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 Operational Characteristics (Protection Circuits Waveforms)
  9. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Power-Down or Undervoltage Lockout (UVLO)
      2. 8.3.2 Power-up
      3. 8.3.3 Sleep Mode
      4. 8.3.4 New Charge Cycle
      5. 8.3.5 Overvoltage-Protection (OVP) – Continuously Monitored
      6. 8.3.6 Power Good Indication ( PG)
      7. 8.3.7 CHG Terminal Indication
    4. 8.4 Device Functional Modes
      1. 8.4.1  CHG and PG LED Pull-up Source
      2. 8.4.2  Auto Start-up (BQ24041)
      3. 8.4.3  IN-DPM (VIN-DPM or IN-DPM)
      4. 8.4.4  OUT
      5. 8.4.5  ISET
      6. 8.4.6  PRE_TERM – Pre-Charge and Termination Programmable Threshold, BQ24040/5
      7. 8.4.7  ISET2
      8. 8.4.8  TS (BQ24040/5)
      9. 8.4.9  Termination and Timer Disable Mode (TTDM) - TS Terminal High
      10. 8.4.10 Timers, BQ24040 and BQ24045 only
      11. 8.4.11 Termination
      12. 8.4.12 Battery Detect Routine
      13. 8.4.13 Refresh Threshold
      14. 8.4.14 Starting a Charge on a Full Battery
  10. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Typical Application: BQ24040 and BQ24045
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Calculations
            1. 9.2.1.2.1.1 Program the Fast Charge Current, ISET:
            2. 9.2.1.2.1.2 Program the Termination Current Threshold, ITERM:
            3. 9.2.1.2.1.3 TS Function (BQ24040)
            4. 9.2.1.2.1.4 CHG and PG
          2. 9.2.1.2.2 Selecting In and Out Terminal Capacitors
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Typical Application Circuit: BQ24041, with ASI and ASO
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
  11. 10Power Supply Recommendations
  12. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
      1. 11.3.1 Leakage Current Effects on Battery Capacity
  13. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 サード・パーティ製品に関する免責事項
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 ドキュメントの更新通知を受け取る方法
    4. 12.4 サポート・リソース
    5. 12.5 Trademarks
    6. 12.6 静電気放電に関する注意事項
    7. 12.7 用語集
  14. 13Mechanical, Packaging, and Orderable Information

Thermal Considerations

The BQ2404x family is packaged in a thermally enhanced MLP package. The package includes a thermal pad to provide an effective thermal contact between the IC and the printed circuit board (PCB). The power pad should be directly connected to the VSS terminal. Full PCB design guidelines for this package are provided in the application note entitled: QFN/SON PCB Attachment Application Report. The most common measure of package thermal performance is thermal impedance (RθJA ) measured (or modeled) from the chip junction to the air surrounding the package surface (ambient). The mathematical expression for RθJA is:

Equation 8. RθJA = (TJ – T) / P

where

  • TJ = Chip junction temperature
  • T = Ambient temperature
  • P = Device power dissipation

Factors that can influence the measurement and calculation of RθJA include:

  1. Whether or not the device is board mounted
  2. Trace size, composition, thickness, and geometry
  3. Orientation of the device (horizontal or vertical)
  4. Volume of the ambient air surrounding the device under test and airflow
  5. Whether other surfaces are in close proximity to the device being tested

Due to the charge profile of Li-Ion and Li-Pol batteries the maximum power dissipation is typically seen at the beginning of the charge cycle when the battery voltage is at its lowest. Typically after fast charge begins the pack voltage increases to ≉3.4V within the first 2 minutes. The thermal time constant of the assembly typically takes a few minutes to heat up so when doing maximum power dissipation calculations, 3.4V is a good minimum voltage to use. This is verified, with the system and a fully discharged battery, by plotting temperature on the bottom of the PCB under the IC (pad should have multiple vias), the charge current and the battery voltage as a function of time. The fast charge current will start to taper off if the part goes into thermal regulation.

The device power dissipation, P, is a function of the charge rate and the voltage drop across the internal PowerFET. It can be calculated from the following equation when a battery pack is being charged:

Equation 9. P = [V(IN) – V(OUT)] × I(OUT) + [V(OUT) – V(BAT)] × I(BAT)

The thermal loop feature reduces the charge current to limit excessive IC junction temperature. It is recommended that the design not run in thermal regulation for typical operating conditions (nominal input voltage and nominal ambient temperatures) and use the feature for non typical situations such as hot environments or higher than normal input source voltage. With that said, the IC will still perform as described, if the thermal loop is always active.