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TPSM82813: Soft start setting

yoshifumi hayashi
Prodigy 10 points
Part Number: TPSM82813

I have a question about the soft start time of the TPSM82813.
8 Parameter Measurement Information
The Css listed in 8.1 Schematic is 47n.
If you calculate Tramp with this 4.7nF capacity, it will be about 1.128ms.
Figure 10-20 The startup timing is about 1ms.
Described as a maximum of 200us for Tramp, as described in 7.5 Electrical Properties.
Isn't this 200us the time when the capacitor is not connected to the SS pin? (Fastest rise time)

What is the maximum playing card time for this device?
(What is the maximum capacity of the capacitor connected to the SS pin?)

  • 0
    TI__Expert 7595 points

    Hi User,

    Thanks for your question.

    Yes you are right, with a Css of 4.7nF we should obtain a Tramp ~ 1.12ms, on top of which we have to consider the variations of the external capacitor (typ =+/-10%) and of the SS/TR Pin Source Current (from 2.1 to 2.8uA).

    The table 7.5 Electrical Characteristics refers indeed to a Tramp measured when we leave the SS/TR Pin open, therefore no capacitor is connected.

    I don't think that we have any strict requirements on the maximum Css, but I would advise to test your actual requirements in the real application.

    Please ask again if you have any more questions.

    Thanks,

    Stefano

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).