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Original question:

TPS40210: TPS40210 overcurrent protection always starts at only 6 Watt output power

TPS40210: TPS40210 soft start consult

Lin_Charles
Expert 4260 points
Part Number: TPS40210

Hi all, it is nice to find you here. When I read the soft start function of TPS40210, I cannot understand it well. Below is the picture in the datasheet, I have some questions about it

1. What VSSE stand for, can you point the specific location in the Figure 21 in datasheet? Vss is always higher than Vsse by 0.7V after T1, right?

2. Why Vout rise from T2 not T1?

3. After Vout get final regulated value, the Vss still rises up, what is the reason? 

Thank you for your help on these questions, Thanks again.

 

  • 0
    TI__Mastermind 46905 points
    Hi Charles

    The VSS is voltage at SS pin, and VSSE is a internal signal to control the FB voltage during softstart. The VSSE is 700mV less than VSS.

    At the beginning of the softstart, the FB voltage is higher than VSSE, so the device don't switch to boost the VOUT. Only when VSSE is higher than FB, the IC start to switch.

    After the VSSE is higher than reference voltage 0.7V, the VOUT is regulated by the reference voltage. The VSSE doesn't impact the normal operation of the boost after this time.