SLUSCU6C August   2017  – January 2020 UCC256301

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Schematic
  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 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Hybrid Hysteretic Control
      2. 7.3.2  Regulated 12-V Supply
      3. 7.3.3  Feedback Chain
      4. 7.3.4  Optocoupler Feedback Signal Input and Bias
      5. 7.3.5  System External Shut Down
      6. 7.3.6  Pick Lower Block and Soft Start Multiplexer
      7. 7.3.7  Pick Higher Block and Burst Mode Multiplexer
      8. 7.3.8  VCR Comparators
      9. 7.3.9  Resonant Capacitor Voltage Sensing
      10. 7.3.10 Resonant Current Sensing
      11. 7.3.11 Bulk Voltage Sensing
      12. 7.3.12 Output Voltage Sensing
      13. 7.3.13 High Voltage Gate Driver
      14. 7.3.14 Protections
        1. 7.3.14.1 ZCS Region Prevention
        2. 7.3.14.2 Over Current Protection (OCP)
        3. 7.3.14.3 Over Output Voltage Protection (VOUTOVP)
        4. 7.3.14.4 Over Input Voltage Protection (VINOVP)
        5. 7.3.14.5 Under Input Voltage Protection (VINUVP)
        6. 7.3.14.6 Boot UVLO
        7. 7.3.14.7 RVCC UVLO
        8. 7.3.14.8 Over Temperature Protection (OTP)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Burst Mode Control
      2. 7.4.2 High Voltage Start-Up
      3. 7.4.3 X-Capacitor Discharge
      4. 7.4.4 Soft-Start and Burst-Mode Threshold
      5. 7.4.5 System States and Faults State Machine
      6. 7.4.6 Waveform Generator State Machine
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  LLC Power Stage Requirements
        2. 8.2.2.2  LLC Gain Range
        3. 8.2.2.3  Select Ln and Qe
        4. 8.2.2.4  Determine Equivalent Load Resistance
        5. 8.2.2.5  Determine Component Parameters for LLC Resonant Circuit
        6. 8.2.2.6  LLC Primary-Side Currents
        7. 8.2.2.7  LLC Secondary-Side Currents
        8. 8.2.2.8  LLC Transformer
        9. 8.2.2.9  LLC Resonant Inductor
        10. 8.2.2.10 LLC Resonant Capacitor
        11. 8.2.2.11 LLC Primary-Side MOSFETs
        12. 8.2.2.12 Design Considerations for Adaptive Dead-Time
        13. 8.2.2.13 LLC Rectifier Diodes
        14. 8.2.2.14 LLC Output Capacitors
        15. 8.2.2.15 HV Pin Series Resistors
        16. 8.2.2.16 BLK Pin Voltage Divider
        17. 8.2.2.17 BW Pin Voltage Divider
        18. 8.2.2.18 ISNS Pin Differentiator
        19. 8.2.2.19 VCR Pin Capacitor Divider
        20. 8.2.2.20 Burst Mode Programming
        21. 8.2.2.21 Soft-Start Capacitor
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 VCC Pin Capacitor
    2. 9.2 Boot Capacitor
    3. 9.3 RVCC Pin Capacitor
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support (if applicable)
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.10 Resonant Current Sensing

The ISNS pin is connected to the resonant capacitor using a high voltage capacitor. The capacitor CISNS and the resistor RISNS form a differentiator. The resonant capacitor voltage is differentiated to get the resonant current. The differentiated signal is AC and goes both positive and negative. In order to sense the zero crossing, the signal is level shifted using an op amp adder. IPolarity comparator detects the direction of the resonant current. The digital state machine implements a blanking time on IPolarity – IPolarity edges during the first 400ns of dead time are ignored.

OCP2 and OCP3 thresholds are based on average input current. To get the average input current, the differentiator output is multiplexed with the high side switch on signal HSON: when HS is on, the MUX output is the differentiator output; when HS is off, the MUX output is 0. The MUX output is then averaged using a low pass filter. The output of the filter is the sensed average input current. Note that the MUX needs to pass through both positive and negative voltages. OCP2 and OCP3 faults have a 2ms and 50ms timer respectively. Only when the OCP2/OCP3 comparators output high for continuous 2ms or 50ms, the faults will be activated.

OCP1 threshold is set on the peak resonant current. The voltage on the ISNS pin gets compared to OCP1 threshold OCP1Th directly. The peak resonant current is checked once per cycle on the positive half cycle. OCP1 fault is only activated when there are 4 consecutive cycles of OCP1 event detected. During start up, the OCP1 comparator output of the first 15 cycles are ignored.

UCC256301 fig42_sluscu6.gifFigure 35. ISNS Block Diagram