SLUSAF2C February   2011  – April 2015

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (Continued)
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  Battery Voltage Regulation
      2. 9.3.2  Battery Current Regulation
      3. 9.3.3  Battery Precharge Current Regulation
      4. 9.3.4  Input Current Regulation
      5. 9.3.5  Charge Termination, Recharge, and Safety Timers
      6. 9.3.6  Power Up
      7. 9.3.7  Input Undervoltage Lockout (UVLO)
      8. 9.3.8  Input Overvoltage/Undervoltage Protection
      9. 9.3.9  Enable and Disable Charging
      10. 9.3.10 System Power Selector
      11. 9.3.11 Converter Operation
      12. 9.3.12 Automatic Internal Soft-Start Charger Current
      13. 9.3.13 Charge Overcurrent Protection
      14. 9.3.14 Charge Undercurrent Protection
      15. 9.3.15 Battery Detection
        1. 9.3.15.1 Example
      16. 9.3.16 Battery Short Protection
      17. 9.3.17 Battery Overvoltage Protection
      18. 9.3.18 Temperature Qualification and JEITA Guideline
      19. 9.3.19 MOSFET Short Circuit and Inductor Short Circuit Protection
      20. 9.3.20 Thermal Regulation and Shutdown Protection
      21. 9.3.21 Timer Fault Recovery
      22. 9.3.22 Inductor, Capacitor, and Sense Resistor Selection Guidelines
      23. 9.3.23 Charge Status Outputs
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Inductor Selection
        2. 10.2.2.2 Input Capacitor
        3. 10.2.2.3 Output Capacitor
        4. 10.2.2.4 Input Filter Design
        5. 10.2.2.5 Input ACFET and RBFET Selection
      3. 10.2.3 Application Curves
    3. 10.3 System Examples
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Trademarks
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

5 Description (Continued)

The bq24171 charges the battery in three phases: preconditioning, constant current, and constant voltage. The device is adjustable for up to three series Li+ cells.

Charge is terminated when the current reaches 10% of the fast charge rate. A programmable charge timer offers a safety backup. The bq24171 automatically restarts the charge cycle if the battery voltage falls below an internal threshold, and enters a low-quiescent current sleep mode when the input voltage falls below the battery voltage.

The bq24171 features Dynamic Power Management (DPM) to reduce the charge current when the input power limit is reached to avoid overloading the adapter. A highly accurate current-sense amplifier enables precise measurement of input current from adapter to monitor overall system power.

The bq24171 device provides power path selector gate driver ACDRV/CMSRC on input NMOS pair ACFET (Q1) and RBFET (Q2), and BATDRV on a battery PMOS device (Q3). When the qualified adapter is present, the system is directly connected to the adapter. Otherwise, the system is connected to the battery. In addition, the power path prevents battery from boosting back to the input.

The bq24171 charges battery from DC source as high as 17 V, including car battery. The input overvoltage limit is adjustable through the OVPSET pin. The AVCC, ACP and ACN pins are 30-V rating. When a high-voltage DC source is inserted, Q1 and Q2 remain off to avoid high voltage damage to the system.

For 1-cell applications, if the battery is not removable, the system can be directly connected to the battery to simplify the power path design and reduce the cost. With this configuration, the battery can automatically supplement the system load if the adapter is overloaded.

The bq24171 is available in a 24-pin, 5.5-mm × 3.5-mm thin QFN package.