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TPS62740: TPS62740 - 100% Mode

Fabio Leitao
Prodigy 120 points
Part Number: TPS62740

Hi,

When Vin decreases to VTH_100, the TPS62740 enters into 100% duty cycle mode.
What is the efficiency during this status?

Thank you.

Fabio

  • 0
    TI__Mastermind 19210 points

    Hi Fabio,

    Unfortunately we do not have efficiency plots for 100% mode operation. However, you can use Webench to calculate efficiency at any desired condition.

    Regards,

    Febin

  • 0 in reply to Febin
    Prodigy 120 points

    I was not able to recreate this state using Webench. When I set the input voltage similar to the output voltage ( to enable the 100% mode) there's an error  message saying that the minimum input voltage is too low for the desired output.
    Could you please confirm this configuration? Or explain how I could achive this simulation?
    Thank you



  • 0 in reply to Fabio Leitao
    TI__Mastermind 19210 points

    Hi Fabio,

    I will try to simulate it on Webench.

    Could you please share the desired test conditions?

    Regards,

    Febin

  • 0 in reply to Febin
    Prodigy 120 points

    Hi Febin,

    The desired output voltage is 2.8V. And I would like to check the regulator efficiency when Vin goes down, reaches the VTH_100 value and starts following the input until Vin = 2.8V.

    Really appreciate your support. 

    Fabio

  • 0 in reply to Fabio Leitao
    TI__Mastermind 19210 points

    Hi Fabio,

    There is a minimum input voltage that needs to be supplied to get an output of 2.8V. This is to compensate for the switching losses in the MOSFET and DC losses in the inductor. It is a buck converter and the efficiency is not 100% due to these losses.

    I simulated TPS62740 with the following conditions on Webench: Vin 3.05V, Vout 2.8V, Iout 0.3A; the efficiency was 91.7%. Please remember that when the BOM changes, the efficiency could vary accordingly. I used the standard BOM for this simulation.

    Regards,

    Febin

  • 0 in reply to Febin
    Prodigy 120 points

    Hi Febin,
    Thank you for the simulation.
     Can we assume that in 100% mode (when the input reached the configured 2.8V and the output starts following the input and both decreasing), the efficiency is 100%?

    Thank you

  • 0 in reply to Fabio Leitao
    TI__Mastermind 19210 points

    Hi Fabio,

    For a falling Vin, I would assume that the device is now in 100% mode. The efficiency will not be 100% in any case.

    When VIN–VOUT falls below VTH_100- the device enters 100% Mode by turning the high side MOSFET on. The 100% Mode is exited when VIN–VOUT exceeds VTH_100+ and the device starts switching.

    Regards,

    Febin

  • 0 in reply to Febin
    TI__Mastermind 19210 points

    Hi Fabio,

    Do you have further questions? If not, I will close this thread.

    Regards,

    Febin

  • 0 in reply to Febin
    Prodigy 120 points

    Hi Febin, 
    Just one last question.
    I've tried to use the spice model of the TPS62740. The description appears as " TPS62740 PSpice Unencrypted Transient Model (Rev. A)", however, I seems actually encrypted. Could you please check the model or provide an uncrypted version?

    Thank you for your attention.

    Fabio.

  • 0 in reply to Fabio Leitao
    TI__Mastermind 19210 points

    Hi Fabio,

    You are correct. It looks like 'Encrypted'

    TPS62740_TRANS.lib

    Here is the Unencrypted .lib file. Please use this file instead of the original .lib file in the project folder. Please make sure you use the same name as the old .lib file.

    Regards,

    Febin

  • 0 in reply to Febin
    TI__Mastermind 19210 points

    Hi Fabio,

    Do you need further support on this issue? If not, I will go ahead and close this thread.

    Regards,

    Febin