SLUS618I August   2004  – December 2014

UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Power Flow Diagram
  5. 5 Revision History
  6. 6 Description (continued)
  7. 7 Device Options
  8. 8 Pin Configuration and Functions
  9. 9 Specifications
    1. 9.1 Absolute Maximum Ratings
    2. 9.2 ESD Ratings
    3. 9.3 Recommended Operating Conditions
    4. 9.4 Thermal Information
    5. 9.5 Dissipation Ratings
    6. 9.6 Electrical Characteristics
    7. 9.7 Typical Characteristics
  10. 10Detailed Description
    1. 10.1 Overview
    2. 10.2 Functional Block Diagram
    3. 10.3 Feature Description
      1. 10.3.1  bq24038 Differences
      2. 10.3.2  Power-Path Management
        1. 10.3.2.1 Case 1: AC Mode (PSEL = High)
          1. 10.3.2.1.1 System Power
          2. 10.3.2.1.2 Charge Control
          3. 10.3.2.1.3 Dynamic Power-Path Management (DPPM)
        2. 10.3.2.2 Case 2: USB (PSEL = Low) bq24030/31/32A/38
          1. 10.3.2.2.1 System Power
          2. 10.3.2.2.2 Charge Control
          3. 10.3.2.2.3 Dynamic Power-Path Management (DPPM)
          4. 10.3.2.2.4 Battery Temperature Monitoring
      3. 10.3.3  Charge Status Outputs
      4. 10.3.4  ACPG, USBPG Outputs (Power Good), bq24030/31/32A/35
      5. 10.3.5  PG Output (Power Good), bq24038
      6. 10.3.6  CE Input (Chip Enable)
      7. 10.3.7  VBSEL Input (Battery Voltage Selection), bq24038
      8. 10.3.8  DPPM Used As A Charge Disable Function
      9. 10.3.9  Timer Fault Recovery
      10. 10.3.10 Short-Circuit Recovery
      11. 10.3.11 LDO Regulator
    4. 10.4 Device Functional Modes
      1. 10.4.1 Sleep Mode - V(IN) < VI(BAT)
      2. 10.4.2 Standby Mode - V(IN) > VI(BAT)and CE (Chip Enable) Pin = Low
      3. 10.4.3 Battery Charge Mode - V(IN) > VI(BAT), Battery Present, CE Pin = High and DPPM Pin Not Floating
        1. 10.4.3.1 Autonomous Power Source Selection, PSEL Control Pin
      4. 10.4.4 Charge Control
        1. 10.4.4.1 Battery Pre-Conditioning
        2. 10.4.4.2 Battery Charge Current
        3. 10.4.4.3 Battery Voltage Regulation
        4. 10.4.4.4 Power Handoff
        5. 10.4.4.5 Temperature Regulation and Thermal Protection
        6. 10.4.4.6 Charge Timer Operation
        7. 10.4.4.7 Charge Termination and Recharge
      5. 10.4.5 Boot-Up Sequence
  11. 11Application and Implementation
    1. 11.1 Application Information
    2. 11.2 Typical Application
      1. 11.2.1 Design Requirements
      2. 11.2.2 Detailed Design Procedure
        1. 11.2.2.1 Selecting the Input and Output Capacitors
      3. 11.2.3 Application Curves
  12. 12Power Supply Recommendations
  13. 13Layout
    1. 13.1 Layout Guidelines
    2. 13.2 Layout Example
    3. 13.3 Thermal Considerations
  14. 14Device and Documentation Support
    1. 14.1 Device Support
      1. 14.1.1 Third-Party Products Disclaimer
    2. 14.2 Documentation Support
      1. 14.2.1 Related Documentation
    3. 14.3 Related Links
    4. 14.4 Trademarks
    5. 14.5 Electrostatic Discharge Caution
    6. 14.6 Glossary
  15. 15Mechanical, Packaging, and Orderable Information

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6 Description (continued)

The power select pin, PSEL, defines which input source is to be used first (primary source – AC or USB). If the primary source is not available, then the IC automatically switches over to the other secondary source if available or the battery as the last option. If the PSEL is set low, the USB input is selected first and if not available, the AC line is selected (if available) but programmed to a USB input limiting rate (100 mA/500 mA max). This feature allows the use of one input connector, where the host programs the PSEL pin according to what source is connected (AC adaptor or USB port).

The bq24038 replaces USBPG with pin VBSEL, to enable user selection of the charge voltage. In addition, pin ACPG was modified to PG. PG is active low when either ac power or USB power is detected.

The ISET1 pin programs the battery's fast charge constant current level with a resistor. During normal AC operation, the input supply provides power to both the OUT (System) and BAT pins. For peak or excessive loads (typically when operating from the USB power, PSEL = Low) that would cause the input source to enter current limit (or Q3 - USB FET limiting current) and its source and system voltage (OUT pin) to drop, the dynamic power-path management (DPPM) feature reduces the charging current attempting to prevent any further drop in system voltage. This feature allows the selection of a lower current rated adaptor based on the average load (ISYS-AVG + IBAT-PGM ) rather than a high peak transient load.