JAJSW05A March   2020  – January 2025 BQ24800

PRODUCTION DATA  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements
    7. 5.7 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Device Power Up
        1. 6.3.1.1 Battery Only
        2. 6.3.1.2 Adapter Detect and ACOK Output
          1. 6.3.1.2.1 Adapter Overvoltage (ACOV)
        3. 6.3.1.3 REGN LDO
      2. 6.3.2 System Power Selection
      3. 6.3.3 Current and Power Monitor
        1. 6.3.3.1 High Accuracy Current Sense Amplifier (IADP and IDCHG)
        2. 6.3.3.2 High Accuracy Power Sense Amplifier (PMON)
      4. 6.3.4 Processor Hot Indication for CPU Throttling
      5. 6.3.5 Input Current Dynamic Power Management
        1. 6.3.5.1 Setting Input Current Limit
      6. 6.3.6 Two-Level Adapter Current Limit (Peak Power Mode)
      7. 6.3.7 EMI Switching Frequency Adjust
      8. 6.3.8 Device Protections Features
        1. 6.3.8.1 Charger Timeout
        2. 6.3.8.2 Input Overcurrent Protection (ACOC)
        3. 6.3.8.3 Charge Overcurrent Protection (CHG_OCP)
        4. 6.3.8.4 Battery Overvoltage Protection (BATOVP)
        5. 6.3.8.5 Battery Short
        6. 6.3.8.6 Thermal Shutdown Protection (TSHUT)
        7. 6.3.8.7 Inductor Short, MOSFET Short Protection
    4. 6.4 Device Functional Modes
      1. 6.4.1 Battery Charging in Buck Mode
        1. 6.4.1.1 Setting the Charge Current
        2. 6.4.1.2 Setting the Charge Voltage
        3. 6.4.1.3 Automatic Internal Soft-Start Charger Current
      2. 6.4.2 Hybrid Power Boost Mode
      3. 6.4.3 Battery Only Boost Mode
        1. 6.4.3.1 Setting Minimum System Voltage in Battery Only Boost Mode
      4. 6.4.4 Battery Discharge Current Regulation in Hybrid Boost Mode and Battery Only Boost Mode
      5. 6.4.5 Battery LEARN Cycle
      6. 6.4.6 Converter Operational Modes
        1. 6.4.6.1 Continuous Conduction Mode (CCM)
        2. 6.4.6.2 Discontinuous Conduction Mode (DCM)
        3. 6.4.6.3 Non-Sync Mode and Light Load Comparator
    5. 6.5 Programming
      1. 6.5.1 SMBus Interface
        1. 6.5.1.1 SMBus Write-Word and Read-Word Protocols
        2. 6.5.1.2 Timing Diagrams
    6. 6.6 Register Maps
      1. 6.6.1  Battery-Charger Commands
      2. 6.6.2  Setting Charger Options
        1. 6.6.2.1 ChargeOption0 Register
      3. 6.6.3  ChargeOption1 Register
      4. 6.6.4  ChargeOption2 Register
      5. 6.6.5  ChargeOption3 Register
      6. 6.6.6  ProchotOption0 Register
      7. 6.6.7  ProchotOption1 Register
      8. 6.6.8  ProchotStatus Register
      9. 6.6.9  Charge Current Register
      10. 6.6.10 Charge Voltage Register
      11. 6.6.11 Discharge Current Register
      12. 6.6.12 Minimum System Voltage Register
      13. 6.6.13 Input Current Register
      14. 6.6.14 Register Exceptions
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Typical System Schematic
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1  Adapter Current Sense Filter
          2. 7.2.1.2.2  Negative Output Voltage Protection
          3. 7.2.1.2.3  Reverse Input Voltage Protection
          4. 7.2.1.2.4  Reduce Battery Quiescent Current
          5. 7.2.1.2.5  CIN Capacitance
          6. 7.2.1.2.6  L1 Inductor Selection
          7. 7.2.1.2.7  CBATT Capacitance
          8. 7.2.1.2.8  Buck Charging Internal Compensation
          9. 7.2.1.2.9  CSYS Capacitance
          10. 7.2.1.2.10 Battery Only Boost Internal Compensation
          11. 7.2.1.2.11 Power MOSFETs Selection
          12. 7.2.1.2.12 Input Filter Design
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Migration from Previous Devices (Does not Support Battery Only Boost)
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
          1. 7.2.2.2.1 CSYS Capacitance
        3. 7.2.2.3 Application Curves
  9. 8 Power Supply Recommendations
  10. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Examples
      1. 9.2.1 Layout Consideration of Current Path
      2. 9.2.2 Layout Consideration of Short Circuit Protection
      3. 9.2.3 Layout Consideration for Short Circuit Protection
  11. 10Device and Documentation Support
    1. 10.1 サード・パーティ製品に関する免責事項
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 ドキュメントの更新通知を受け取る方法
    4. 10.4 サポート・リソース
    5. 10.5 Trademarks
    6. 10.6 静電気放電に関する注意事項
    7. 10.7 用語集
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

6.3.2 System Power Selection

The BQ24800 device automatically switches adapter or battery power to system. An automatic break-before-make logic prevents shoot-through currents when the selectors switch. The system is powered across the body diode of the BATFET during the brief period between the first selector turning off and the second turning on.

The ACDRV drives a pair of common-source (CMSRC) N-channel power MOSFETs (ACFET and RBFET) between the adapter and ACP. The ACFET separates adapter from system and battery, and limits inrush current when the adapter is plugged in by controlling the ACFET turn-on time. Additionally, it protects the adapter when the system or battery is shorted. The RBFET provides negative input voltage protection and battery discharge protection when adapter is shorted to ground, and minimizes system power dissipation with its low RDS(on) compared to a Schottky diode.

When the voltage measured at the ACDET pin is less than 2.4 V, it is determined that a valid adapter is not present. Under this condition, ACDRV is pulled to CMSRC to keep ACFET and RBFET off, isolating the adapter input from the system rail. BATDRV stays at VBATSRC + 6 V to connect battery to system if all of the following conditions are valid:

  • VVCC > VUVLO
  • VACN < VSRN + 200 mV
  • ACFET/RBFET off

When the voltage measured at the ACDET pin is greater than 2.4 V, a valid adapter is determined to be present. Under this condition, the ACDRV is driven above CMSRC to turn ACFET and RBFET on, and the system power source switches from battery to adapter if all of the following conditions are valid:

  • ACOK high with all conditions in Section 6.3.1.2 valid.
  • Not in LEARN mode
  • In LEARN mode and VSRN < battery depletion threshold

The gate drive voltage on ACFET and RBFET is VCMSRC + 6 V. If the ACFET/RBFET have been turned on for 20 ms, and the voltage across gate and source is still less than 5.7 V, ACFET and RBFET are turned off. After 1.3 sec delay, it resumes turning on ACFET and RBFET. If such a failure is detected seven times within 90 seconds, ACFET/RBFET are latched off and an adapter removal is required to force ACDET < 0.6 V to remove the latch. After the latch is reset, ACFET/RBFET can be turned on again.

To turn off ACFET/RBFET, one of the following conditions must be valid:

  • In LEARN mode and VSRN is above battery depletion threshold;
  • ACOK low

To limit the adapter inrush current during ACFET turn-on, the Cgs and Cgd external capacitor of ACFET must be carefully selected following the guidelines below:

  • Minimize total capacitance on system
  • Cgs should be 40× or higher than Cgd to avoid ACFET false turn on during adapter hot plug-in
  • Fully turn on ACFET within 20 ms, otherwise, charger IC will consider turn-on failure
  • Check with MOSFET vendor on peak current rating
  • Place 4-kΩ resistor in series with ACDRV, CMSRC, and BATDRV pin to limit inrush current