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TPS61165: Soft Start-Up

Takashi Yamaguchi
Genius 11080 points
Part Number: TPS61165
Other Parts Discussed in Thread: TPS92360

Hi team,

My customer is considering to use the TPS61165. 

The datasheet states "32 steps — each step takes 213 μs" for soft start. Which part of the waveform is this in Fig.6? Vout or Comp as shown in the figure below?

Also, why does it take about 2 ms for COMP to start up after CTRL goes High?

Regards,

Yamaguchi

  • 0
    TI__Genius 12915 points

    Hi Yamaguchi,

    The voltage at FB pin ramps up to the reference voltage in 32 steps, which is not showed in this plot. But you could refereed to voltage of COMP since it is the output of internal error amplifier and FB voltage is controlled by it.

    For the delayed time between CTRL and COMP, it is designed for EasyScale mode detection time. If ES mode is used, some special steps need to be performed in this time.

  • 0 in reply to Hardy Wu
    TI__Genius 11080 points

    Hi Hardy,

    Thank you for the answer. I received additional questions from the customer. Could you please help with the questions below?

    1. The customer is connecting 220nF capacitor to the COMP pin. Can the time from CTRL=Hi to the start of IL output be shortened by lowering the capacitance(Ccomp)?  Also, if this capacitance(Ccomp) can be changed, can you tell me if there are any design considerations?

    2. Is it correct to understand that the time from CTRL=Hi to the start of COMP rising will be a fixed time since the customer will not use ES mode this time?
    Also, if it is a fixed time, is the specification to be about 2ms as shown in Figure 6?

    Regards,

    Yamaguchi

  • +1 in reply to Takashi Yamaguchi
    TI__Genius 12915 points

    Hi Yamaguchi,

    1. The capacitor is not only for soft start, but also used to stabilize the feedback loop of the TPS61165. We do not recommend to change the value.

    2. Yes the setup delay time is more than ES mode detection window time. Totally around 2ms and cannot be change.

    Does customer care the response time from CTRL rising to output stable very much? If so, I suggest customer could use other one channel device without ES mode, like TPS92360.