SLUSD90E June   2019  – February 2021 UCC256402 , UCC256403 , UCC256404

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
    1.     Device Comparison Table
  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 13-V Supply
      3. 7.3.3 Feedback Chain
        1. 7.3.3.1 Optocoupler Feedback Signal Input and Bias
        2. 7.3.3.2 FB Pin Voltage Clamp
        3. 7.3.3.3 "Pick Lower Value" Block and Soft Start Multiplexer
        4. 7.3.3.4 Pick Higher Block and Burst Mode Multiplexer
        5. 7.3.3.5 VCR Comparators
      4. 7.3.4 Resonant Capacitor Voltage Sensing
      5. 7.3.5 Resonant Current Sensing
      6. 7.3.6 Bulk Voltage Sensing
      7. 7.3.7 Output Voltage Sensing
      8. 7.3.8 High Voltage Gate Driver
        1. 7.3.8.1 Adaptive Dead Time Control
      9. 7.3.9 Protections
        1. 7.3.9.1 ZCS Region Prevention
        2. 7.3.9.2 Over Current Protection (OCP)
        3. 7.3.9.3 Bias Winding Over Voltage Protection (BWOVP)
        4. 7.3.9.4 Input Under Voltage Protection (VINUVP)
        5. 7.3.9.5 Input Over Voltage Protection (VINOVP)
        6. 7.3.9.6 Boot UVLO
        7. 7.3.9.7 RVCC UVLO
        8. 7.3.9.8 Over Temperature Protection (OTP)
    4. 7.4 Device Functional Modes
      1. 7.4.1 High Voltage Start-Up
      2. 7.4.2 X-Capacitor Discharge
      3. 7.4.3 Burst Mode Control
        1. 7.4.3.1 Soft-Start and Burst-Mode Threshold
        2. 7.4.3.2 BMTL/BMTH Ratio Programming
      4. 7.4.4 System State Machine
  8. 8 Power Supply Recommendations
    1. 8.1 VCC Pin Capacitor
    2. 8.2 Boot Capacitor
    3. 8.3 RVCC Pin Capacitor
  9. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Related Links
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Community Resources
    5. 10.5 Trademarks

7.4.3.2 BMTL/BMTH Ratio Programming

As described in Section 7.3.7, BW pin is multiplex for BMTL/BMTH ratio programming. The programming phase happens only once before startup. After that, the BMTL/BMTH ratio is then fixed, until system restarts after a fault or power recycle. The programming phase occurs right before soft start begins. It sources a constant current and measures the voltage on the pin. Depending on the measured pin voltage, different ratio of BMTL/BMTH is selected as listed in Table 7-2. The required BW equivalent resistance is listed in electrical characteristics section.

Other than selecting different BMTL/BMTH ratios, the option 5 also disables the LL/SS pin initial voltage program phase during startup, and the option 7 disables the burst mode.

Table 7-2 BMTL/BMTH Ratio Programming
OptionBMTL/BMTH
10.95
21
30.9
40.8
50.6 (LL/SS pin initial voltage programming disabled)
60.6
70.4 (Burst Mode Disabled)