SLUSAL0C September   2011  – January 2020 BQ24725A

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 SMBus Interface
    4. 8.4 Device Functional Modes
      1. 8.4.1  Adapter Detect and ACOK Output
      2. 8.4.2  Adapter Over Voltage (ACOVP)
      3. 8.4.3  System Power Selection
      4. 8.4.4  Battery LEARN Cycle
      5. 8.4.5  Enable and Disable Charging
      6. 8.4.6  Automatic Internal Soft-Start Charger Current
      7. 8.4.7  High Accuracy Current Sense Amplifier
      8. 8.4.8  Charge Timeout
      9. 8.4.9  Converter Operation
      10. 8.4.10 Continuous Conduction Mode (CCM)
      11. 8.4.11 Discontinuous Conduction Mode (DCM)
      12. 8.4.12 Input Over Current Protection (ACOC)
      13. 8.4.13 Charge Over Current Protection (CHGOCP)
      14. 8.4.14 Battery Over Voltage Protection (BATOVP)
      15. 8.4.15 Battery Shorted to Ground (BATLOWV)
      16. 8.4.16 Thermal Shutdown Protection (TSHUT)
      17. 8.4.17 EMI Switching Frequency Adjust
      18. 8.4.18 Inductor Short, MOSFET Short Protection
    5. 8.5 Register Maps
      1. 8.5.1 Battery-Charger Commands
      2. 8.5.2 Setting Charger Options
        1. Table 3. Charge Options Register (0x12H)
      3. 8.5.3 Setting the Charge Current
        1. Table 4. Charge Current Register (0x14H), Using 10mΩ Sense Resistor
      4. 8.5.4 Setting the Charge Voltage
        1. Table 5. Charge Voltage Register (0x15H)
      5. 8.5.5 Setting Input Current
        1. Table 6. Input Current Register (0x3FH), Using 10mΩ Sense Resistor
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Typical System with Two NMOS Selector
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Negative Output Voltage Protection
          2. 9.2.1.2.2 Reverse Input Voltage Protection
          3. 9.2.1.2.3 Reduce Battery Quiescent Current
          4. 9.2.1.2.4 Inductor Selection
          5. 9.2.1.2.5 Input Capacitor
          6. 9.2.1.2.6 Output Capacitor
          7. 9.2.1.2.7 Power MOSFETs Selection
          8. 9.2.1.2.8 Input Filter Design
          9. 9.2.1.2.9 BQ24725A Design Guideline
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Simplified System without Power Path
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
    3. 9.3 System Examples
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 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

9.2.1 Typical System with Two NMOS Selector

BQ24725A is SMBus controlled customizable charge controller, and can be configured for automatic system power source selection, by utilizing two charge pumps to separately drive n-channel MOSFETs (ACFET, RBFET and BATFET). BQ24725A automatically switches adapter or battery power to system. An automatic break-before-make logic prevents shoot-through currents when the selectors switch.

BQ24725A sch1_NMOS_lusaL0.gif
Fs = 750kHz, IADPT = 4.096A, ICHRG = 2.944A, ILIM = 4A, VCHRG = 12.592V, 90W adapter and 3S2P battery pack
Use 0Ω for better current sensing accuracy, use 10Ω/7.5Ω resistor for reversely battery connection protection. See application information about negative output voltage protection for hard shorts on battery to ground or battery reversely connection.
The total Csys is the lump sum of system capacitance. It is not required by charger IC. Use Ri and Ci for adapter hot plug-in voltage spike damping. See application information about input filter design.
Figure 18. Typical System Schematic with Two NMOS Selector

Table 7. Component List for Typical System Circuit of Figure 18

PART DESIGNATOR QTY DESCRIPTION
C1, C2, C3, C13, C14, C16 6 Capacitor, Ceramic, 0.1µF, 25V, 10%, X7R, 0603
C4 1 Capacitor, Ceramic, 100pF, 25V, 10%, X7R, 0603
C5, C6 2 Capacitor, Ceramic, 1µF, 25V, 10%, X7R, 0603
C7 1 Capacitor, Ceramic, 0.047µF, 25V, 10%, X7R, 0603
C8, C9, C10, C11 4 Capacitor, Ceramic, 10µF, 25V, 10%, X7R, 1206
C15 1 Capacitor, Ceramic, 0.01µF, 25V, 10%, X7R, 0603
C17 1 Capacitor, Ceramic, 2200pF, 25V, 10%, X7R, 0603
Ci 1 Capacitor, Ceramic, 2.2µF, 25V, 10%, X7R, 1210
Csys 1 Capacitor, Electrolytic, 220µF, 25V
D1 1 Diode, Schottky, 30V, 200mA, SOT-23, Fairchild, BAT54
D2 1 Diode, Dual Schottky, 30V, 200mA, SOT-23, Fairchild, BAT54C
Q1, Q2, Q5 3 N-channel MOSFET, 30V, 12.5A, SO-8, Fairchild, FDS6680A
Q3, Q4 2 N-channel MOSFET, 30V, 12A, PowerPAK 1212-8, Vishay Siliconix, SiS412DN
Q6 1 N-channel MOSFET, 50V, 0.2A, SOT-323, Diodes, BSS138W
L1 1 Inductor, SMT, 4.7µH, 5.5A, Vishay Dale, IHLP2525CZER4R7M01
R1 1 Resistor, Chip, 430kΩ, 1/10W, 1%, 0603
R2 1 Resistor, Chip, 66.5kΩ, 1/10W, 1%, 0603
R3, R4, R5 3 Resistor, Chip, 10kΩ, 1/10W, 1%, 0603
R6, R10, R11 3 Resistor, Chip, 4.02kΩ, 1/10W, 1%, 0603
R7 1 Resistor, Chip, 316kΩ, 1/10W, 1%, 0603
R8 1 Resistor, Chip, 100kΩ, 1/10W, 1%, 0603
R9 1 Resistor, Chip, 10Ω, 1/4W, 1%, 1206
R12 1 Resistor, Chip, 1.00MΩ, 1/10W, 1%, 0603
R13 1 Resistor, Chip, 3.01MΩ, 1/10W, 1%, 0603
R14 1 Resistor, Chip, 10Ω, 1/10W, 5%, 0603
R15 1 Resistor, Chip, 7.5Ω, 1/10W, 5%, 0603
RAC, RSR 2 Resistor, Chip, 0.01Ω, 1/2W, 1%, 1206
Ri 1 Resistor, Chip, 2Ω, 1/2W, 1%, 1210
U1 1 Charger controller, 20 pin VQFN, TI, BQ24725ARGR
U2 1 Dual digital transistor, 40V, 30mA, SC-74, Rohm, IMD2A