SLUSD90C June   2019  – March 2020 UCC256402 , UCC256403 , UCC256404


  1. Features
  2. Applications
  3. Description
    1.     Simplified Schematic
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
    1.     Pin Functions
  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 Switching Characteristics
    7. 7.7 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Hybrid Hysteretic Control
      2. 8.3.2 Regulated 13-V Supply
      3. 8.3.3 Feedback Chain
        1. Optocoupler Feedback Signal Input and Bias
        2. FB Pin Voltage Clamp
        3. "Pick Lower Value" Block and Soft Start Multiplexer
        4. Pick Higher Block and Burst Mode Multiplexer
        5. VCR Comparators
      4. 8.3.4 Resonant Capacitor Voltage Sensing
      5. 8.3.5 Resonant Current Sensing
      6. 8.3.6 Bulk Voltage Sensing
      7. 8.3.7 Output Voltage Sensing
      8. 8.3.8 High Voltage Gate Driver
        1. Adaptive Dead Time Control
      9. 8.3.9 Protections
        1. ZCS Region Prevention
        2. Over Current Protection (OCP)
        3. Bias Winding Over Voltage Protection (BWOVP)
        4. Input Under Voltage Protection (VINUVP)
        5. Input Over Voltage Protection (VINOVP)
        6. Boot UVLO
        7. RVCC UVLO
        8. Over Temperature Protection (OTP)
    4. 8.4 Device Functional Modes
      1. 8.4.1 High Voltage Start-Up
      2. 8.4.2 X-Capacitor Discharge
      3. 8.4.3 Burst Mode Control
        1. Soft-Start and Burst-Mode Threshold
        2. BMTL/BMTH Ratio Programming
      4. 8.4.4 System State Machine
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1.  LLC Power Stage Requirements
        2.  LLC Gain Range
        3.  Select Ln and Qe
        4.  Determine Equivalent Load Resistance
        5.  Determine Component Parameters for LLC Resonant Circuit
        6.  LLC Primary-Side Currents
        7.  LLC Secondary-Side Currents
        8.  LLC Transformer
        9.  LLC Resonant Inductor
        10. LLC Resonant Capacitor
        11. LLC Primary-Side MOSFETs
        12. LLC Rectifier Diodes
        13. LLC Output Capacitors
        14. HV Pin Series Resistors
        15. BLK Pin Voltage Divider
        16. ISNS Pin Differentiator
        17. VCR Pin Capacitor Divider
        18. BW Pin Voltage Divider
        19. Soft Start and Burst Mode Programming
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 VCC Pin Capacitor
    2. 10.2 Boot Capacitor
    3. 10.3 RVCC Pin Capacitor
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Related Links
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

Pin Configuration and Functions

DDB Package
16-Pin SOIC (Pins 2, 13 removed)
Top View
UCC256402 UCC256403 UCC256404 pinout-01-slusd90.gif

Pin Functions

BLK 4 I This pin is used to sense the LLC stage input voltage level. A resistor divider should be used to attenuate the signal before it is applied to this pin. The voltage level on this pin will determine when the LLC converter starts/stops switching.
BW 8 I This pin is used to sense the output voltage through the bias winding. The sensed voltage is used for output over voltage protection. During startup, the pin is also used to program the ratio between the two burst mode thresholds (BMTL and BMTH).
FB 5 I LLC stage control feedback input. The amount of current sourced from this pin will determine the LLC input power level.
GND 11 G Ground reference for all signals.
HB 14 I High-side gate-drive floating supply voltage. The bootstrap capacitor is connected between this pin and HS pin. A high voltage, high speed diode should be connected from RVCC to this pin to supply power to the high-side gate-driver during the period when the low-side MOSFET is conducting.
HO 15 O High-side floating gate-drive output.
HS 16 I High-side gate-drive floating ground. Current return for the high-side gate-drive current.
HV 1 I Connects to internal HV startup JFET. For UCC256402 and UCC256404, this pin provides start up power for both PFC and LLC stage. This pin also monitors the AC line voltage for x-capacitor discharge function. For UCC256403, this pin needs to be connected to ground.
ISNS 6 I Resonant current sense. The resonant capacitor voltage is differentiated with a first order filter to measure the resonant current.
LL/SS 9 I The capacitance value connected from this pin to ground will impact the duration of the soft-start period. The resistor divider connected to the pin will define the initial voltage applied on the pin for startup. After system startup, this pin is used to program the burst mode threshold.
LO 10 O Low-side gate-drive output.
Removed 2 N/A Functional creepage and clearance
Removed 13 N/A Functional creepage and clearance
RVCC 12 P Regulated 13-V supply. This pin is used to supply the gate driver and PFC controller.
VCC 3 P Supply input.
VCR 7 I Resonant capacitor voltage sense.