SLUSFU9 October   2024 BQ51013C

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Description (continued)
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Details of a Qi Wireless Power System and BQ51013C Power Transfer Flow Diagrams
      2. 8.3.2  Dynamic Rectifier Control
      3. 8.3.3  Dynamic Efficiency Scaling
      4. 8.3.4  RILIM Calculations
      5. 8.3.5  Input Overvoltage
      6. 8.3.6  Adapter Enable Functionality and EN1/EN2 Control
      7. 8.3.7  End Power Transfer Packet (WPC Header 0x02)
      8. 8.3.8  Status Outputs
      9. 8.3.9  WPC Communication Scheme
      10. 8.3.10 Communication Modulator
      11. 8.3.11 Adaptive Communication Limit
      12. 8.3.12 Synchronous Rectification
      13. 8.3.13 Temperature Sense Resistor Network (TS)
      14. 8.3.14 3-State Driver Recommendations for the TS/CTRL Pin
      15. 8.3.15 Thermal Protection
      16. 8.3.16 WPC v2.0 Compliance – Foreign Object Detection
      17. 8.3.17 Receiver Coil Load-Line Analysis
    4. 8.4 Device Functional Modes
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 BQ51013C Wireless Power Receiver Used as a Power Supply
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Using The BQ51013C as a Wireless Power Supply: (See Figure 1-1 )
          2. 9.2.1.2.2 Series and Parallel Resonant Capacitor Selection
          3. 9.2.1.2.3 Recommended RX Coils
          4. 9.2.1.2.4 COMM, CLAMP, and BOOT Capacitors
          5. 9.2.1.2.5 Control Pins and CHG
          6. 9.2.1.2.6 Current Limit and FOD
          7. 9.2.1.2.7 RECT and OUT Capacitance
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Dual Power Path: Wireless Power and DC Input
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Wireless and Direct Charging of a Li-Ion Battery at 800 mA
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
        3. 9.2.3.3 Application Curves
  11. 10Power Supply Recommendations
  12. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  13. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
      2. 12.1.2 Development Support
    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
  14. 13Revision History
  15. 14Mechanical, Packaging, and Orderable Information
9.2.1.2.2 Series and Parallel Resonant Capacitor Selection

Shown in Figure 9-1, the capacitors C1 (series) and C2 (parallel) make up the dual resonant circuit with the receiver coil. These two capacitors must be sized correctly per the WPC v2.0 specification. Figure 9-2 illustrates the equivalent circuit of the dual resonant circuit:

BQ51013C Dual Resonant Circuit With the Receiver CoilFigure 9-2 Dual Resonant Circuit With the Receiver Coil

The Power Receiver Design Requirements in Volume 1 of the WPC v2.0 specification highlights in detail the sizing requirements. To summarize, the receiver designer will be required to take inductance measurements with a standard test fixture as shown in Figure 9-3:

BQ51013C WPC v2.0 Receiver Coil Test Fixture For the Inductance Measurement Ls’ (Copied From System Description Wireless Power Transfer, Volume 1: Low Power, Part 1 Interface Definition, Version 1.1)Figure 9-3 WPC v2.0 Receiver Coil Test Fixture For the Inductance Measurement Ls’ (Copied From System Description Wireless Power Transfer, Volume 1: Low Power, Part 1 Interface Definition, Version 1.1)

The primary shield is to be 50 mm × 50 mm × 1 mm of Ferrite material PC44 from TDK Corp. The gap dZ is to be 3.4 mm. The receiver coil, as it will be placed in the final system (for example, the back cover and battery must be included if the system calls for this), is to be placed on top of this surface and the inductance is to be measured at 1-V RMS and a frequency of 100 kHz. This measurement is termed Ls’. The same measurement is to be repeated without the test fixture shown in Figure 9-3. This measurement is termed Ls or the free-space inductance. Each capacitor can then be calculated using Equation 6:

Equation 6. BQ51013C

where

  • fS is 100 kHz +5/-10%.
  • fD is 1 MHz ±10%.

C1 must be chosen first prior to calculating C2.

The quality factor must be greater than 77 and can be determined by Equation 7:

Equation 7. BQ51013C

where

  • R is the DC resistance of the receiver coil.

All other constants are defined above.

For this application, the selected coil inductance, Ls, is 11 µH and the Ls' is 16 µH with a DC resistance of 191 mΩ. Using Equation 6, the C1 resolves to 158.3 nF (with a range of 144 nF to 175 nF). For an optimum solution of 3 capacitors in parallel, the chosen capacitors are 68 nF, 47 nF, and 39 nF for a total of 154 nF, well within the desired range. Using the same equation (and the chosen value for C1), C2 resolves to 2.3 nF. This is easily met with capacitors of 2.2 nF and 100 pF. The C1 and C2 capacitors must have a minimum voltage rating of 25 V. Solving for the quality factor (Q in Equation 7), gives a value of over 500.

Table 9-1 lists the recommended RX coils.