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LM25066: About TIMER operation

Tsukui Yusuke
Guru 21930 points
Part Number: LM25066

Hi,

Could you tell me about timer operation?
I want to mask the inrush current at the LM25066 start up timing.

1.When the power supply ON timing, Does the TIMER pin work?
   I want to mask the only in-rush current using the CTIMER.
　There are two kinds of explanations in the data sheet.

(1)

　

(2)

　

2.Please tell me other ways to mask the inrush current.

Best Regards,
Yusuke

  • 0
    TI__Guru 57737 points
    Hi Yusuke,

    When you say you want to mask the inrush current, do you mean that you want the controller to ignore the inrush current?
    Can you help us understand why you would want to do so?
    Do you have a constraint on startup time?

    By using dv/dt startup, the Cdv/dt is so selected that the inrush current is clamped to a value lower than set current limit and power limit there by not triggering either current limit or Power limit. But,this will increase the time taken for startup.
  • 0 in reply to Praveen GD
    Guru 21930 points

    Praveen-san,

    Thank you for you response.

    〉When you say you want to mask the inrush current, do you mean that you want the controller to ignore the inrush current?
    →Yes.
    〉Can you help us understand why you would want to do so?
    →When the current limit works, the output voltage drops.
    　　I want to start so that voltage drop does not occur.

     〉Do you have a constraint on startup time?
    →Let me check and I will get back to you.

    Best Regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Guru 57737 points
    Hi Yusuke,

    The input voltage drops even more if there is no inrush current limit. this is because, if you do not limit the inrush current, the inrush current can be very high resulting in heavy drop of Vin based on source impedance.
    If you are very concerned about drop in Vin during startup and do not have much concern about startup time, the best way is to use dv/dt based startup.