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

8.3.11 Adaptive Communication Limit

The Qi communication channel is established through backscatter modulation as described in the previous sections. This type of modulation takes advantage of the loosely coupled inductor relationship between the RX and TX coils. Essentially, the switching in-and-out of the communication capacitor or resistor adds a transient load to the RX coil in order to modulate the TX coil voltage and current waveform (amplitude modulation). The consequence of this technique is that a load transient (load current noise) from the mobile device has the same signature. To provide noise immunity to the communication channel, the output load transients must be isolated from the RX coil. The proprietary feature Adaptive Communication Limit achieves this by dynamically adjusting the current limit of the regulator. When the regulator is put in current limit, any load transients will be offloaded to the battery in the system.

Note that this requires the battery charger device to have input voltage regulation (weak adapter mode). The output of the RX appears as a weak supply if a transient occurs above the current limit of the regulator.

The Adaptive Communication Limit feature has two current limit modes and is detailed in Table 8-5.

Table 8-5 Adaptive Communication Limit
IOUTCOMMUNICATION CURRENT LIMIT
< 300 mAFixed 400 mA
> 300 mAIOUT + 50 mA

The first mode is illustrated in Figure 7-18. In this plot, an output load pulse of 300 mA is periodically introduced on a DC current level of 200 mA. Therefore, the 400 mA current limit is enabled. The pulses on VRECT indicate that a communication packet event is occurring. When the output load pulse occurs, the regulator limits the pulse to a constant 400 mA and, therefore, preserves communication. Note that VOUT drops to 4.5 V instead of GND. A charger device with an input voltage regulation set to 4.5 V allows this to occur by offloading the load transient support to the mobile device’s battery.

The second mode is illustrated in Figure 7-19. In this plot, an output pulse of 200 mA is periodically introduced on a DC current level of 400 mA. Therefore, the tracking current mode (IOUT + 50 mA) is enabled. In this mode, the BQ51013C measures the active output current and sets the regulator's current limit 50 mA above this measurement. When the load pulse occurs during a communication packet event, the output current is regulated to 450 mA. As the communication packet event has finished the output load is allowed to increase. Note that during the time the regulator is in current limit VOUT is reduced to 4.5 V and 5 V when not in current limit.