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TPS7A19: How soft start works?

Kazuhiko Hirano
Genius 15008 points
Part Number: TPS7A19

Hello,

 

My customer plans to use TPS7A1901 for Vin = 12V, Vout = 1.8V/0.03A.

They have questions about soft start futures.

How it works?

Could you elaborate?

How much would the Vout ramp time be?

Or, less than how much is the inrush current limited, for how much time?

 

Best regards,

 

K.Hirano

  • 0
    TI__Mastermind 23361 points

    Hi Hirano-san, 

    Most LDO that have soft-start will have controlled output ramping during the startup. This is achieved by having a controlled slew rate when powering on the reference of the error amplifier inside the LDO. The soft-start can help minimize the in-rush during the initial startup. TPS7A19, however, does not have a dedicated soft-start or NR pin that allows external control on the ramp speed. Figure 14 in the datasheet shows the soft-start provides a typical slew rate of 3V/ms during the startup. The in-rush can be estimated by Q = C x V = dt x I = C x dV, so I = C x dV/dt; the in-rush will be C x dv/dt + Iload. 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    TI__Genius 15008 points

    Jason,

     

    Thank you for your response.

    I appreciate it.

     

    Best regards,

     

    K.Hiarno