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TLV733P: About inrush current generated at startup

Kaji@PAN
Mastermind 7025 points
Part Number: TLV733P

Hello,

I'm using a TVL73333PDQNR device.
I would like to ask you about the inrush current at startup.
The circuit diagram is shown below.
The current is measured at the red circle at startup, but 512mA flows at the peak.
It is considered that such a peak current is generated due to the charge to the output capacitor.
In steady state, it is 49mA.

(Question 1)
Is it okay to go into a foldback current limit every time the device boots?
Please let me know if you have any concerns.

(Question 2)
Does the foldback current limiting function take into account the inrush current due to charging the capacitor?
Or is it considered only in the case of a short circuit?

Best regards,

  • +1
    TI__Genius 12345 points

    Hi Kaji, 

    Do you happen to have any scope shots of this? 

    The current limit is specified from 360mA to 700mA.

    So at 512mA this might be triggered. Furthermore, if 49mA is the expected load, then 512mA is quite a large inrush current. Here are some ways to improve this: 

    • f you are enabling the TLV733P long after the input voltage is present, then increasing Cin will help lower the initial surge of current.
    • If the TLV733P enable is tied directly to the input pin, then you will look at what is powering the linear regulator to reduce the inrush
      • In this scenario, slowing down the rise time of the power source to the linear regulator will lower the inrush current

    Typically, our devices can handle this type of scenarios, so as a protective feature, it is good. 

    Even in the case that our LDOs can survive large inrush current events, it is not advisable as this could degrade the reliability of the part in a long term basis.

    Best, 

    Edgar Acosta