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LMR62014 Start-up time

tateo yamashiro
Guru 10890 points
Other Parts Discussed in Thread: LMR62014

Hi,

My customer has questions about LMR62014.
Could you tell me about questoins?

[Questions]
- Does the LMR62014 have soft-start function?
- How much is the start-up time?

Best Regards,
tateo

  • 0
    TI__Genius 15810 points
    Hello,
    Upon application of input voltage, since the device is not yet switching, the output immediately flies to a diode drop below VIN. Then after a short delay of about 100 us, the device ramps to VOUT in another 100 us. I hope this helps.

    Regards,
    Akshay
  • 0
    TI__Mastermind 19891 points

    Hello Yamashiro-san,


    I could not see any information on a softstart function. I will try to find this information from the IC designers.

    In the meantime, here is a scope shot from the evaluation board for this part. It shows you the ramp up time of Vout.

    Regards,
    Denislav

  • 0 in reply to Denislav Petkov
    TI__Genius 15810 points

    Hello,

    Denislav and I have looked into the operation of this device and have realized that the output voltage rise will depend on the slew rate of the input voltage. There is no internal soft start on this device. If the input voltage was brought up slowly like Denislav has shown in the previous reply, then the output voltage will follow Vin and have a relatively slower softstart. If Vin is already on and EN is brought up externally, then the scenario I presented takes place. Here is the snapshot of that. 

    In addition to this, here are a few startup waveforms with different VIN slew rates.

    Here is 1 ms VIN slew rate.

    Here is 2.5 ms VIN slew rate

    Here is 5 ms VIN slew rate

    And finally here is the 10 ms VIN slew rate

    We hope this answers your questions.