SLUSA75B July   2010  – January 2020 BQ24650

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 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 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Battery Voltage Regulation
      2. 8.3.2  Input Voltage Regulation
      3. 8.3.3  Battery Current Regulation
      4. 8.3.4  Battery Precharge
      5. 8.3.5  Charge Termination and Recharge
      6. 8.3.6  Power Up
      7. 8.3.7  Enable and Disable Charging
      8. 8.3.8  Automatic Internal Soft-Start Charger Current
      9. 8.3.9  Converter Operation
      10. 8.3.10 Synchronous and Non-Synchronous Operation
      11. 8.3.11 Cycle-by-Cycle Charge Undercurrent
      12. 8.3.12 Input Overvoltage Protection (ACOV)
      13. 8.3.13 Input Undervoltage Lockout (UVLO)
      14. 8.3.14 Battery Overvoltage Protection
      15. 8.3.15 Cycle-by-Cycle Charge Overcurrent Protection
      16. 8.3.16 Thermal Shutdown Protection
      17. 8.3.17 Temperature Qualification
      18. 8.3.18 Charge Enable
      19. 8.3.19 Inductor, Capacitor, and Sense Resistor Selection Guidelines
      20. 8.3.20 Charge Status Outputs
      21. 8.3.21 Battery Detection
        1. 8.3.21.1 Example
    4. 8.4 Device Functional Modes
      1. 8.4.1 Converter Operation
      2. 8.4.2 Synchronous and Non-Synchronous Operation
  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 Inductor Selection
        2. 9.2.2.2 Input Capacitor
        3. 9.2.2.3 Output Capacitor
        4. 9.2.2.4 Power MOSFETs Selection
        5. 9.2.2.5 Input Filter Design
        6. 9.2.2.6 MPPT Temperature Compensation
      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 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.21 Battery Detection

For applications with removable battery packs, the BQ24650 provides a battery absent detection scheme to reliably detect insertion or removal of battery packs.

BQ24650 batt_flow_lusa75.gifFigure 12. Battery Detection Flowchart

When the device has powered up, a 6-mA discharge current is applied to the SRN terminal. If the battery voltage falls below the LOWV threshold within 1 second, the discharge source is turned off, and the charger is turned on at low charge current (125 mA). If the battery voltage gets up above the recharge threshold within 500 ms, there is no battery present and the cycle restarts. If either the 500 ms or 1 second timer time out before the respective thresholds are hit, a battery is detected and a charge cycle is initiated.

BQ24650 batt_tim_dia_lusa75.gifFigure 13. Battery Detect Timing Diagram

Take care that the total output capacitance at the battery node is not so large that the discharge current source cannot pull the VFB voltage below the LOWV threshold during the 1 second discharge time. The maximum output capacitance can be calculated according to Equation 9:

Equation 9. BQ24650 EQ9_cmax_lusa75.gif

where

  • CMAX is the maximum output capacitance,
  • IDISCH is the discharge current,
  • tDISCH is the discharge time,
  • and R2 and R1 are the voltage feedback resistors from the battery to the VFB pin.

The 0.5 factor is the difference between the RECHARGE and the LOWV thresholds at the VFB pin.