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LM61480-Q1: Designs with LM61480QRPHRQ1 do not Export to TINA-TI and WEBBENCH Simulation with LM61480QRPHRQ1 does not simulate an Input Transient properly when set to low current outputs.

Stephen Gilbert
Prodigy 10 points
Part Number: LM61480-Q1
Other Parts Discussed in Thread: TINA-TI, LM61480, PSPICE-FOR-TI, LMR43610-Q1

Our IT Department just installed TINA-TI on my laptop today 5/06/2022. I have several designs on the TI WEBENCH Power tool involving DC-DC converters.  When I click on the Export button in the upper right of the WEBENCH screen, I then get the option to export to TINA-TI.  A small Tab at the bottom of the page appears with starting download.  Every time after approximately 5  to 10 seconds, The small Tab displays "EXPORT FAILED" I have tried several times with the same result. Any help would be greatly appreciated. The Texas Instruments DC-DC converter being simulated is LM61480QRPHRQ1. The input voltage is set to 20 - 36VDC, The output voltage is set to 5.0VDC. The output current is set to 430mA.  I have tried the online WEBench tool for simulating of the Input Transient response and the output voltage shown never reaches the desired set voltage of 5Volts. I believe the reason is because the time axis on the WEBence tool is not adjustable and if it was allowed to run long enough, the voltage would indeed reach 5Volts. That is why I had our I.T. department install TINA-TI as the simulation time is supposed to be adjustable.  I know that the device that I am using  (LM61480QRPHRQ1) is an 8A device but the data sheet states that it will operate at an output current of 0 to 8 Amps. I have two issues: 1. Why does the design (shown) not export into the Texas Instruments simulation tool TINA-TI, and 2. I would like a Texas Instruments FAE or representative to confirm that the LM61480QRPHRQ1 will indeed operate and is stable at relative low output currents since the WEBench tool does not confirm this, (as low a 0 Amps ,as the data sheet states).  Thank you.

 Stephen Gilbert

  • 0
    TI__Mastermind 47060 points

    Hi Stephen,

    I can confirm that the LM61480 will be stable at lower load currents, even at no load. 

    TINA-TI has been slowly phased out for PSPICE-FOR-TI so I would suggest you download the simulation tool and use the existing PSpice Transient model for your verification purposes. This can be found in the "Design & development" section of the LM61480 product folder. 

    The EVM is another way for customers to evaluate the part's performance. Please see the User's Guide for more information. The EVM is set for 5Vout|400kHz with application curves showcasing the part's performance in Section 6 (https://www.ti.com/lit/ug/snvu682a/snvu682a.pdf#page=12). 

    You will notice that the device is regulating to 5V even at 0A (refer to Figure 6-9 and Figure 6-10) for both Auto-Mode and FPWM-Mode operations.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Prodigy 10 points

    Thank you for answering my questions and for the suggestion of using the newer simulation tool.  One last question:  Due to size constraints, I designed the DC-DC Power supply to run at a switching frequency of 836kHz and used the WEBench design for 20 to 36VDC in, 5VDC out and even though I probably will never use the full power of the device, I set the design parameter at 8 Amps output and followed the WEBench tool exactly for all values.  I assume that this will still be stable and operate properly at currents below 1 amp?  Is this true?  Thank you again as you have been a great help.

     

    Regards,

     

    Stephen Gilbert

  • +1 in reply to Stephen Gilbert
    TI__Mastermind 47060 points

    Hi Stephen,

    Yes that should be okay.

    Is there a reason why you chose a high current device over the lower current devices? It looks like your application is going to run 430mA so I would have suggested the LMR43610-Q1 device which is small and should have a more optimized efficiency around that low current application.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Prodigy 10 points

    Jimmy,

     

    The power supply is for an earth orbiting satellite and we wanted to use either space rated or at the very least automotive grade components. At the time the design was started, and it still  looks this way, that was the only component with reasonable availability that was at least AEC-Q100 or Q200 qualified. I would like to have designed in a lower current automotive quality device but due to the world wide component situation, the availability is sometimes over a year for such components.  At the time we could get and bought all of the LM61480 automotive grade components that we could find. I am designing another board now but can’t find an automotive grade DC-DC converter that will operate from 20VDC to 36VDC and output low current unless I am willing to wait many months.  So, in short, we had to buy what was available even though we recognized that the converters were overkill.  Thank you for your quick response. You have been a great help.  You have answered my questions.

     

    Regards,

     

    Stephen Gilbert