SLUS756D September   2007  – June 2026 BQ24751A

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
    1. 4.1 Terminal Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 Recommended Operating Conditions
    3. 5.3 Package Thermal Data
    4. 5.4 Electrical Characteristics
    5. 5.5 Typical Charateristics
  7. 6 Detailed Description
    1. 6.1  Functional Block Diagram
    2. 6.2  Battery Voltage Regulation
    3. 6.3  Battery Current Regulation
    4. 6.4  Input Adapter Current Regulation
    5. 6.5  Adapter Detect and Power Up
    6. 6.6  Enable and Disable Charging
    7. 6.7  System Power Selector
    8. 6.8  Battery Learn Cycles
    9. 6.9  Automatic Internal Soft-Start Charger Current
    10. 6.10 Converter Operation
    11. 6.11 Synchronous and Non-Synchronous Operation
    12. 6.12 High Accuracy IADAPT Using Current Sense Amplifier (CSA)
    13. 6.13 Input Overvoltage Protection (ACOV)
    14. 6.14 Input Undervoltage Lock Out (UVLO)
    15. 6.15 Battery Overvoltage Protection
    16. 6.16 Battery Shorted (Battery Undervoltage) Protection
    17. 6.17 Charge Overcurrent Protection
    18. 6.18 Thermal Shutdown Protection
    19. 6.19 Adapter Detected Status Register ( ACGOOD Pin)
    20. 6.20 Input Over-Power Protection (ACOP)
      1. 6.20.1 Conditions for ACOP Latch Off:
  8. 7 Application Information
    1. 7.1 Input Capacitance Calculation
    2. 7.2 PCB Layout Design Guideline
  9. 8 Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

6.4 Input Adapter Current Regulation

The total input current from an AC adapter or other DC sources is a function of the system supply current and the battery charging current. System current normally fluctuates as portions of the systems are powered up or down. Without Dynamic Power Management (DPM), the source must be able to supply the maximum system current and the maximum charger input current simultaneously. By using DPM, the input current regulator reduces the charging current when the input current exceeds the input current limit set by ACSET. The current capacity of the AC adapter can be lowered, reducing system cost.

Similar to setting battery-regulation current, adapter current is sensed by resistor RAC connected between ACP and ACN. Its maximum value is set by ACSET, which is ratiometric with respect to VDAC, using Equation 3.

Equation 3. bq24751A

The input voltage range of ACSET is between 0 and VDAC, up to 3.6 V.

The ACP and ACN pins are used to sense RAC with a default value of 10 mΩ. However, resistors of other values can also be used. A larger sense-resistor value yields a larger sense voltage, and a higher regulation accuracy. However, this is at the expense of a higher conduction loss.