SLUAAT3 November   2023 TPS56837

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Why Soft Start is Needed
  5. 2Soft Start Principle
    1. 2.1 General Principle
    2. 2.2 Internal and External Soft Start
  6. 3Behaviors Related to Soft Start of TPS56837
    1. 3.1 Soft Start Sequence
    2. 3.2 Soft Start Discharge
    3. 3.3 UVP Hiccup Time
  7. 4How to Co-Lay TPS56837 and TPS56637
    1. 4.1 Pinout Differences of TPS56837 and TPS56637
    2. 4.2 Co-lay Guidance TPS56837 and TPS56637
  8. 5Summary
  9. 6References

3.2 Soft Start Discharge

If the external soft start capacitor Css has pre-biased voltage at start-up, the device initially discharges the external capacitor voltage to lower voltage then charge again. This discharge is intended to prevent power up without soft start when the pre-biased voltage is higher than reference voltage.

Figure 3-2 shows TPS56837 soft start waveform when external Css has pre-biased voltage. Once EN is enabled, TPS56837 begins to discharge the pre-biased Css. When the voltage of Css reaches zero, the soft start function begins and Vout ramps up smoothly.

GUID-20231121-SS0I-WZQL-WQ21-FDSHNZZLPHR5-low.svg Figure 3-2 Discharge When External Css has Pre-bias Voltage