SLUSES3B October   2023  – July 2024 UCC25660

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Input Power Proportional Control
        1. 7.3.1.1 Voltage Feedforward
      2. 7.3.2 VCR Synthesizer
      3. 7.3.3 Feedback Chain (Control Input)
      4. 7.3.4 Adaptive Dead-Time
      5. 7.3.5 Input Voltage Sensing
        1. 7.3.5.1 Brown in and Brown out Tresholds and Options
        2. 7.3.5.2 Output OVP and External OTP
      6. 7.3.6 Resonant Tank Current Sensing
    4. 7.4 Protections
      1. 7.4.1 Zero Current Switching (ZCS) Protection
      2. 7.4.2 Minimum Current Turn-off During Soft Start
      3. 7.4.3 Cycle by Cycle Current Limit and Short Circuit Protection
      4. 7.4.4 Overload (OLP) Protection
      5. 7.4.5 VCC OVP Protection
    5. 7.5 Device Functional Modes
      1. 7.5.1 Startup
        1. 7.5.1.1 With HV Startup
        2. 7.5.1.2 Without HV Startup
      2. 7.5.2 Soft Start Ramp
        1. 7.5.2.1 Startup Transition to Regulation
      3. 7.5.3 Light Load Management
        1. 7.5.3.1 Operating Modes (Burst Pattern)
        2. 7.5.3.2 Mode Transition Management
        3. 7.5.3.3 Burst Mode Threshold Programming
        4. 7.5.3.4 PFC On/Off
      4. 7.5.4 X-Capacitor Discharge
        1. 7.5.4.1 Detecting Through HV Pin Only
  9. 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 ISNS Pin Differentiator
        18. 8.2.2.18 TSET Pin
        19. 8.2.2.19 OVP/OTP Pin
        20. 8.2.2.20 Burst Mode Programming
        21. 8.2.2.21 Application Curves
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 VCCP Pin Capacitor
      2. 8.3.2 Boot Capacitor
      3. 8.3.3 V5P Pin Capacitor
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
        1. 8.4.2.1 Schematics
        2. 8.4.2.2 Schematics
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.5.3.3 Burst Mode Threshold Programming

Burst mode programming is set by external resistor divider connected to V5P. During the programming phase, a constant current ILLPrgm is fed to the pin and the resulting voltage is measured via ADC (VLLA) at time TLLPrgm. After TPrgm, ILLPrgm is turned off and the voltage of the LL resistor divider is measured (VLLB).

UCC25660 UCC25660

Figure 7-20 LL pin Programming

The voltage on the LL pin after switch S1 is off (VLLB) is directly used to set the input power at which the system stops the LF Burst segment(PacketStop).

Based on the measured VLLB voltage and the difference in voltage between VLLA and VLLB, theFBReplica voltage at which the controller enters HF Burst cant be determined. This can be calculated from the PacketStop/HFBurstEntry ratio given in TABLE below. Apart from this, option to disable burst mode features itself is also provided.

The equation to claculate VLLA - VLLB is given below. where

Equation 7. VLLA - VLLB = (Ru||Rl)*ILLprgm
Ru||Rl = Rth

The FBReplica at which the controllers starts the LF Burst segment is given below.

Equation 8. LFBurstEntry = PacketStop/0.6
Table 7-2 Burst Mode Externally programable Settings
VLLA- VLLB (V) PacketStop/HFBurstEntry ratio Comment
>2.41 0.45
2.185 NA Burst disable
1.754 0.50 LF frequency range 200Hz to 400Hz
1.391 0.55 LF frequency range 200Hz to 400Hz
1.087 0.60 LF frequency range 200Hz to 400Hz
0.833 0.65 LF frequency range 200Hz to 400Hz
0.617 0.70 LF frequency range 200Hz to 400Hz
0.441 0.75 LF frequency range 200Hz to 400Hz
0.176 0.80 LF frequency range 200Hz to 400Hz

The ability to directly set the input power at which the system goes into various low power modes, dynamically disabling the burst mode enables an extra degree of freedom in the system design.