ZHCSAF0E September   2012  – January 2018

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用范围
  3. 3 说明
    1.     典型应用电路
  4. 4 修订历史记录
  5. 5 说明 （续）
  6. 6 Device Comparisons
  7. 7 Pin Configuration and Functions
    1.     Pin 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 Timing Requirements
    7. 8.7 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagrams
    3. 9.3 Operational Flow Chart
    4. 9.4 Feature Description
      1. 9.4.1 Input Voltage Protection
        1. 9.4.1.1 Input Overvoltage Protection
        2. 9.4.1.2 Bad Adaptor Detection/Rejection
        3. 9.4.1.3 Sleep Mode
        4. 9.4.1.4 Input Voltage Based DPM (Special Charger Voltage Threshold)
      2. 9.4.2 Battery Protection
        1. 9.4.2.1 Output Overvoltage Protection
        2. 9.4.2.2 Battery Detection at Power Up in DEFAULT Mode
        3. 9.4.2.3 Battery Short Protection
        4. 9.4.2.4 Battery Detection in Host Mode
      3. 9.4.3 DEFAULT Mode
      4. 9.4.4 USB Friendly Power Up
      5. 9.4.5 Input Current Limiting At Power Up
    5. 9.5 Device Functional Modes
      1. 9.5.1 Charge Mode Operation
        1. 9.5.1.1 Charge Profile
      2. 9.5.2 PWM Controller in Charge Mode
      3. 9.5.3 Battery Charging Process
      4. 9.5.4 Thermal Regulation and Protection
      5. 9.5.5 Charge Status Output, STAT Pin
      6. 9.5.6 Control Bits in Charge Mode
        1. 9.5.6.1 CE Bit (Charge Mode)
        2. 9.5.6.2 RESET Bit
        3. 9.5.6.3 OPA_Mode Bit
      7. 9.5.7 Control Pins in Charge Mode
        1. 9.5.7.1 CD Pin (Charge Disable)
      8. 9.5.8 BOOST Mode Operation
        1. 9.5.8.1 PWM Controller in Boost Mode
        2. 9.5.8.2 Boost Start Up
        3. 9.5.8.3 PFM Mode at Light Load
        4. 9.5.8.4 Protection in Boost Mode
          1. 9.5.8.4.1 Output Overvoltage Protection
          2. 9.5.8.4.2 Output Overload Protection
          3. 9.5.8.4.3 Battery Overvoltage Protection
        5. 9.5.8.5 STAT Pin in Boost Mode
      9. 9.5.9 High Impedance (Hi-Z) Mode
    6. 9.6 Programming
      1. 9.6.1 Serial Interface Description
        1. 9.6.1.1 F/S Mode Protocol
        2. 9.6.1.2 H/S Mode Protocol
        3. 9.6.1.3 I2C Update Sequence
        4. 9.6.1.4 Slave Address Byte
        5. 9.6.1.5 Register Address Byte
    7. 9.7 Register Description
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Typical Application
        1. 10.1.1.1 Design Requirements
        2. 10.1.1.2 Detailed Design Procedure
      2. 10.1.2 Charge Current Sensing Resistor Selection Guidelines
      3. 10.1.3 Output Inductor and Capacitance Selection Guidelines
    2. 10.2 Typical Performance Curves
  11. 11Power Supply Recommendations
    1. 11.1 System Load After Sensing Resistor
      1. 11.1.1 The Advantages:
      2. 11.1.2 Design Requirements and Potential Issues:
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 接收文档更新通知
    3. 13.3 Community Resources
    4. 13.4 商标
    5. 13.5 静电放电警告
    6. 13.6 Glossary
  14. 14机械、封装和可订购信息
    1. 14.1 封装概要
      1. 14.1.1 芯片级封装尺寸

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

10.1.1.2 Detailed Design Procedure

Systems Design Specifications:

  • VBUS = 5 V
  • VBAT = 4.2 V (1-Cell)
  • I(charge) = 1.25 A
  • Inductor ripple current = 30% of fast charge current
  1. Determine the inductor value (LOUT) for the specified charge current ripple:

    2. bq24157 q_lo_vbat_lus824.gif, the worst case is when battery voltage is as close as to half of the input voltage.

    Equation 1. bq24157 q_lo_25_lus824.gif

    LOUT = 1.11 μH

    Select the output inductor to standard 1 μH. Calculate the total ripple current with using the 1-μH inductor:

    Equation 2. bq24157 q_dlo_vbat_lus824.gif
    Equation 3. bq24157 q_dlo_25_lus824.gif

    ΔIL = 0.42 A

    Calculate the maximum output current:

    Equation 4. bq24157 q_lpk_io_lus824.gif
    Equation 5. bq24157 q_lpk_125_lus824.gif

    ILPK = 1.46 A

    Select 2.5mm by 2mm 1-μH 1.5-A surface mount multi-layer inductor. The suggested inductor part numbers are shown as following.

    Table 10. Inductor Part Numbers(1)

    PART NUMBERINDUCTANCESIZEMANUFACTURER
    LQM2HPN1R0MJ0 1 μH 2.5 x 2.0 mm Murata
    MIPS2520D1R0 1 μH 2.5 x 2.0 mm FDK
    MDT2520-CN1R0M 1 μH 2.5 x 2.0 mm TOKO
    CP1008 1 μH 2.5 x 2.0 mm Inter-Technical

    spacer

  2. Determine the output capacitor value (COUT) using 40 kHz as the resonant frequency:
    3. Equation 6. bq24157 q_fo_lus824.gif
    Equation 7. bq24157 q_cout_1_lus824.gif
    Equation 8. bq24157 q_cout_2_lus824.gif

    COUT = 15.8 μF

    Select two 0603 X5R 6.3V 10-μF ceramic capacitors in parallel i.e., Murata GRM188R60J106M.

  3. Determine the sense resistor using the following equation:
    4. Equation 9. bq24157 q_rsns_vsns_lus824.gif

    The maximum sense voltage across the sense resistor is 85 mV. In order to get a better current regulation accuracy, V(RSNS) should equal 85mV, and calculate the value for the sense resistor.

    Equation 10. bq24157 q_rsns_85_lus824.gif

    R(SNS) = 68 mΩ

    This is a standard value. If it is not a standard value, then choose the next close value and calculate the real charge current. Calculate the power dissipation on the sense resistor:

    P(RSNS) = I(CHARGE)2 × R(SNS)

    P(RSNS) = 1.252 × 0.068

    P(RSNS) = 0.106 W

    Select 0402 0.125-W 68-mΩ 2% sense resistor, i.e. Panasonic ERJ2BWGR068.

  4. Measured efficiency and total power loss with different inductors are shown in Figure 24. SW node and inductor current waveform are shown in Figure 34.
bq24157 pwr_loss_lus824.gifFigure 24. Measured Efficiency and Power Loss