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LM5012: What is the minimum time required to switch from standby mode to active mode at full load condition?

Ravi Teja Arumalla
Prodigy 20 points
Part Number: LM5012
Other Parts Discussed in Thread: LM5013

Hi,

I want to Turn ON and Turn OFF my Buck converter (LM5012DDAR) using EN/UVLO pin voltage. 

May I know what is the minimum time required to switch the IC function from standby mode to active mode in steady state operation? 

Also what is the minimum and maximum frequency of the PWM signal I can apply at EN/UVLO pin to switch the functions between standby and active modes at full load condition?

Is there any Spice model to check the above functionality?

Thanks and Regards

Ravi

  • +1
    TI__Guru* 78070 points

    Hi Ravi,

    Thank you for posting. Referring to datasheet Figure 9-6, IC delay time from being enabled to active switching mode is up to ~100us, and most of it is taken to initialize the internal logic. Please also note that the internal soft-start time which may delay Vout rise to regulation level.  However, turn-off should be immediate with <100ns propagation delay when EN drops below the threshold.  

    Depending on what is your desired output status, you can apply PWM to EN/UVLO as you wish.  

    Sorry at this moment we do not have the spice model for this device.  However, we do have the LM5013 EVM and you can order and replace the IC with the LM5012, and run some test. 

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 20 points

    Hi Youhao

    Thanks for the reply. I have a query.

    Does the internal soft-start time delay (3 ms) always exists, while IC is transitioning from Shutdown mode or Standby Mode to Active mode?

    Thanks and Regards

    Ravi

  • 0 in reply to Ravi Teja Arumalla
    TI__Guru* 78070 points

    Hi Ravi,

    Let me double check for you with our design team.

    Thanks,

    Youhao

  • +1 in reply to Youhao Xi
    TI__Guru* 78070 points

    Hi Ravi,

    I just got the confirmation that the SS will always function when the IC transitions from standby or shutdown to active switching mode.

    Hope this clarifies.

    Best Regards,

    Youhao

  • +1 in reply to Youhao Xi
    Prodigy 20 points

    Hi Youhao,

     I got the clarification. Thanks for the Reply. 

    Can we reduce this soft-start time from 3ms to 1.75ms (which is minimum as per data sheet)? If so may I know how to do that?

    Regards

    Ravi