SLUAAF9 September   2021 UCC28782

 

  1.   Trademarks
  2. 1 Initial Board Visual Inspection and Start-up Check
  3. 2 Typical System Operating Waveforms
    1. 2.1 SBP2 Mode
    2. 2.2 SBP1 Mode
    3. 2.3 LPM mode
    4. 2.4 LPM to ABM Mode Transition
    5. 2.5 ABM Mode
    6. 2.6 ABM to AAM Mode Transition
    7. 2.7 AAM Mode
  4. 3Typical System Protection Waveforms
    1. 3.1 Over-Power Protection (OPP)
    2. 3.2 Output Overvoltage Protection (OVP)
    3. 3.3 Output Short-Circuit Protection (SCP)
  5. 4Common Issues and Solutions
    1. 4.1 VDD Boost Converter Survival Mode
      1. 4.1.1 Survival Mode Due To Boost Inductor DCR Too High.
      2. 4.1.2 System Stays In Survival Mode When the Output Voltage is Low Such as 3.3V/5V/9V
    2. 4.2 10% Load Efficiency Might not Meet spec. in USB-PD Application, Especially at 5 V/9 V Output Condition
    3. 4.3 Transient
      1. 4.3.1 BIN/BSW Pin Damage During LPM to ABM Mode Transition
      2. 4.3.2 SR MOSFET VDS Overstress at Survival Mode
      3. 4.3.3 SR MOSFET Vds Voltage Overstress Due to PWMH Partial Turn On At Load Transition
  6. 5References

2 Typical System Operating Waveforms

UCC28782 contains six modes of operation that summarized in UCC28782 data sheet Table 8-1. From no load to full load, the operation modes include Survival Mode, SBP2(Second StandBy Power Mode), SBP1, (First StandBy Power Mode) LPM (Low Power Mode), ABM (Adaptive Burst Mode), AAM (Adaptive Amplitude Modulation), The survival mode only kicks in when VDD voltage lower than the 13-V survival mode threshold and also performs the clamping capacitor balancing function to reduce the voltage stress of the secondary side rectifier. Typically, the system does not enter survival mode during regular load change, such as smooth load increase and decrease. The survival mode might kick in at a large output load remove, overshoot on output results in controller stop switching in a long time, then the VDD voltage might drop to touch the 13-V survival mode threshold. The following waveforms show each mode operation (no load to full load).