SLUAA69 July   2020  – MONTH  TPS548D22

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 LED Driver Methods
    2. 1.2 Power Supply Solutions for Common-Cathode LED Display
  3. 2Principle of Synchronous Buck with Sinking Current Application
  4. 3 Design Considerations and Analysis
    1. 3.1 Choose an IC with Sufficient Current Sinking
    2. 3.2 Choose IC Supporting Negative OCP
    3. 3.3 Choose an IC Supporting Pre-Bias Startup
    4. 3.4 Analysis of System Startup
  5. 4 TI Devices and Functionalities
    1. 4.1 Negative OCP Functionality
    2. 4.2 Hiccup Mode and Latch-off Mode
    3. 4.3 UVP and OVP Functionality
  6. 5 TI Solution
  7. 6 Bench Test and Result
    1. 6.1 Bench Test Configuration
    2. 6.2 Startup Waveforms and Behaviors Analysis Overview
    3. 6.3 Startup Waveforms and Behaviors Analysis at the First OVP
    4. 6.4 Startup Waveforms and Behaviors Analysis after the First OVP
    5. 6.5 Waveforms and Behaviors Analysis of Startup Solution with Lazy Loading
  8. 7 Conclusion
  9. 8References

4.2 Hiccup Mode and Latch-off Mode

TPS548D22 supports latch-off mode or hiccup mode when an OVP or UVP event are triggered. Normally when an OVP event occurs, the output discharge could lead to an undervoltage condition and trigger an UVP event. Then the OVP event will be reset by the UVP event. When an OCP event occurs, it results in the output voltage falling which causes the UVP event.

For latch-off mode, the device will shut down if an OVP or UVP event occurs. It will restart again only if the EN pin is toggled or the VDD pin is power cycled. For hiccup mode, the device will restart after a hiccup delay when OVP or UVP are triggered. The hiccup blanking time depends on the soft-start ramp time setting. For a typical 1-ms soft-start, the hiccup blanking time is 16 ms. During the hiccup blanking time, the soft-start logic takes 1 ms to gradually increase the reference voltage from zero to the target level.