• State Resolved
  • Locked Locked
  • Replies 15 replies
  • Subscribers 62 subscribers
  • Views 452 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS62A02: Question about bode plot simulation.

Kazuya Nakai59
Guru 22295 points

Part Number: TPS62A02

Tool/software:

Hello guys,

One of my customers is considering evaluating TPS62A02DRLR for their new products.

At this moment, they have the following questions.
Could you please give me your reply?

Q1.
They want to use a feed forward capacitor which is placed between VOUT and FB terminal for higher speed response in PSM.
They know TPS62A02 bode plot can be simulated by WEBENCH of this device.
But the simulation circuit of WEBENCH doesn't have the feed forward capacitor.  
When they want to execute bode plot simulation for TPS62A02, do they need to use PSPICE for TI?

Or a feed forward capacitor can be added to WEBENCH schematic?

Q2.
They think output voltage oscillation is not occurred because TPS62A02  use a comparator at FB input not a error amplifier.
So they think bode plot can not be simulated on TPS62A02. 

Is their thought not correct?  
In case of an adaptive off time control scheme, can bode plot be simulated?  
Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    TI__Genius 10000 points

    Hi Kazuya,

    Thanks for using E2E.

    If you would like to simulate with the feed forward capacitor you have to use PSpice for TI but we have a transient model only, bode plot simulation is not possible for this device so far.

    The TPS62A02 is using an error amplifier at the FB input.

    Best regards,
    Sepp

  • 0 in reply to Josef Marsmann
    Guru 22295 points

    Hi Sepp,

    Thank you very much for your reply.

    Could I ask you the following additional questions?

    Q1.
    Please let me confirm.
    I understand that TPS62A02 bode plot PSpice simulation is not possible
    because PSpice model for bode plot is not available.
    Also I understand that     the way to simulate TPS62A02 phase margin is WEBENCH only 
    but even WEBENCH cannot simulate the phase margin of a schematic with a feedforward capacitor.
    As the result, I understand it is no way to simulate a bode plot with a feedforward capacitor. 
    Are these my understanding correct?

    Q2.
    Is the only way to confirm the phase margin with a feed forward capacitor to evaluate using EVM or any actual board? 

    Q3.
    Is there any calculator to determine the value of the feed forward capacitor?
    Their output capacitor values are 22uF or 22uFx2. So they think a feed forward capacitor can be placed. 
    They want to know the feed forward capacitor value.

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 10000 points

    Hi Kazuya,

    Q1 Correct

    Q2 Right now, Yes. But we are working with the Webench team to add the cap asap.

    Q3 Unfortunately we don't have a calculator for this device

    I will inform you at the time when the feed forward cap is implemented in Webench.

    Best regards,
    Sepp

  • 0 in reply to Josef Marsmann
    Guru 22295 points

    Hi Sepp,

    Thank you very much for your reply. Your reply really helpful for us.

    Also thank you again for your working with the Webench team to add the feed forward cap.

    We are glad to hear this feed forward cap implementation plan.

    Could I ask you a question about this implementation?

    Q. 
    How long will this implementation take roughly?
    Is it 1month? 2months? Or more?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 10000 points

    Hi Kazuya,

    I got the information that in about 1 month we should see the update.

    Best regards,
    Sepp

  • 0 in reply to Josef Marsmann
    Guru 22295 points

    Hi Sepp,

    Thank you very much for your reply.

    I got it.

    Could you please tell me when the implementation is completed?

    Thank you again and best regards,
    Kazuya. 

  • 0 in reply to Kazuya Nakai59
    Guru 22295 points

    Hi Sepp,

    Thank you very much for your supports.

    How is progress of a feed-forward capacitor implementation to TPS62A02 Webench?

    If it take still a few weeks to complete it, the customer wants to see an actual bode plot 
    with feed-forward capacitor.

    Does TI have any bode plot which taken on an actual board?

    Thank you again and best regards,
    Kazuya.    

  • 0 in reply to Kazuya Nakai59
    TI__Genius 10000 points

    Hi Kazuya,

    We expect feedback from the Webench team by tomorrow about there timeline. 

    Could  you please provide the conditions for the bode plots: Vin, Vout, output capacitance, so I can take a look or do the measurement.

    Best regards,
    Sepp

  • 0 in reply to Josef Marsmann
    Guru 22295 points

    Hi Sepp,

    Thank you very much for your reply.

    The customer has several conditions as the follows.

    1. Vin=4.2V, Vo=1.0V, Io= 402mA, Cout=10uF+22uF, L=1uF, RfbH=56k+47kohm, RfbL=100kohm

    2. Vin=4.2V, Vo=1.2V, Io= 150mA, Cout=10uF+10uF L=1uF,  RfbH=100kohm, RfbL=100kohm

    3. Vin=4.2V, Vo=1.5V, Io= 213mA, Cout=10uF+10uF L=1uF,  RfbH=150kohm, RfbL=100kohm

    4. Vin=4.2V, Vo=3.3V, Io= 92mA, Cout=22uF+22uF L=1uF,  RfbH=330k+120kohm, RfbL=100kohm

    If you need more information, please let me know.

    Thank again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    Guru 22295 points

    Hi Sepp,

    Thank you very much for your strong supports.

    I'm sorry that I missed to input two customer conditions.
    Also I mistook RfbH value in condition No.1.
    So total conditions are the follows.

    1. Vin=4.2V, Vo=1.0V, Io= 402mA, Cout=10uF+22uF, L=1uF, RfbH=56k+4.7kohm, RfbL=100kohm

    2. Vin=4.2V, Vo=1.2V, Io= 150mA, Cout=10uF+10uF L=1uF,  RfbH=100kohm, RfbL=100kohm

    3. Vin=4.2V, Vo=1.2V, Io= 181mA, Cout=10uF+22uF L=1uF,  RfbH=100kohm, RfbL=100kohm

    4. Vin=4.2V, Vo=1.2V, Io=  40mA, Cout=10uF+22uF L=1uF,  RfbH=100kohm, RfbL=100kohm

    5. Vin=4.2V, Vo=1.5V, Io= 213mA, Cout=10uF+10uF L=1uF,  RfbH=150kohm, RfbL=100kohm

    6. Vin=4.2V, Vo=3.3V, Io= 92mA, Cout=22uF+22uF L=1uF,  RfbH=330k+120kohm, RfbL=100kohm

    Did you get any schedule information of new Webench?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 10000 points

    Hi Kazuya,

    I should get the possibility to use Webench with Cff for testing in the next days.

    You can use the current Webench to do the simulation for the conditions above because you don't use a Cff, correct?

    I will inform you when the new Webench is online.

    Best regards,
    Sepp

  • 0 in reply to Josef Marsmann
    Guru 22295 points

    Hi Sepp,

    Thank you for your strong supports and I'm sorry to be late my response.

    Yes, the customer can use the current Webench to do the simulation for the conditions above.

    But they want to add 120pF Cff to confirm how much undershoot and overshoot of output voltage is reduced at load transient. Also they want to check bode plot with the Cff.

    We are looking forward to using the new Webench of TPS62A02 .

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 10000 points

    Hi Kazuya,

    Thanks for your patience. I will inform you when it is available.

    Best regards,
    Sepp

  • 0 in reply to Josef Marsmann
    TI__Genius 10000 points

    Hi Kazuya,

    Now it's possible to simulate with Cff, but after enabling you have to change the value to 120pF.

    Bes regards,
    Sepp

  • 0 in reply to Josef Marsmann
    Guru 22295 points

    Hi Sepp,

    Thank you very much for your supports and the information.

    We will try to use it.

    Thank you again and best regards,
    Kazuya.