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TPS54424: Questions of TPS54424

Jimmy Lai
Expert 6845 points
Part Number: TPS54424
Other Parts Discussed in Thread: TPS564252, TPS564257,

Dear Team,

Looking forward to your answer of my questions. 

And we have run some simulation on TI’s WEBENCH and found some of them not able to reach 90% efficiency. Since it is evaluating for a fanless system so the efficiency is quite important relatively.

Would you please suggest us the suitable parts for our DC/DC solution with the requirements listed below?

  1. Efficiency >90% at least.
  2. Vout tolerance must < 1%.
  3. Cost is sensitive, the cheaper the better.
  4. 12VIN
  5. Vout/Iout:1.88V/0.766A  and 1.8V/ 1.333A and 1.2V/ 2.284A

Many Thanks,

Jimmy

  • 0
    TI__Expert 7320 points

    Hi Jimmy,

    For 1.88V/0.766A and 1.8V/1.333A, the TPS564252 can support ±1% reference accuracy at 25°C, >90% efficiency and it's a low cost device.

    For 1.2V/2.284A, it's difficult to reach 90% efficiency unless you choose a converter with higher rated current (maybe 8A or higher), which means higher cost.

    You can align with our customer to see if they can accept lower efficiency (still >80%) considering low cost.

  • 0 in reply to Athos Zhao
    TI__Expert 6845 points

    Hi Zhao,

    Thanks for your great support. After these days, I have tried and convinced our customer to loose the requirement of efficiency. Now they could accept that it is better to have >85% efficiency but >90% is no longer a hard requirement due to we show them the improvement on efficiency isn’t help thermal relief that much.

    And I have checked the solutions that you recommended. Please see my reply inline[12/13-A].

    For 1.88V/0.766A and 1.8V/1.333A, the TPS564252 can support ±1% reference accuracy at 25°C, >90% efficiency and it's a low cost device.

    [12/13-A]

    For TPS564252 of 1.88V/0.766A application, this is a 4-A solution and with internal soft-start and power good functions. But TPS564252 is fixed Eco-mode buck converter. I may choose TPS564257 and which is fixed FCCM-mode. Please let me know which is the cheapest and which is the most expensive between these parts TPS54424/TPS564252/TPS564257. To be determined whether they’re suitable solutions.

    The simulation result of TPS564252, efficiency is above 91% overall but will have a huge drop to 90% instantly while output current ~0.6A is reached. Why is that? And it’s Vout tolerance is 1.14%.

    The simulation result of TPS564257, efficiency isn’t that good as TPS564252 but approaching 90% while heavy load. Probably could be accepted due to mentioned above that loose the requirement of efficiency. Vout tolerance is the same 1.14%.

    For 1.2V/2.284A, it's difficult to reach 90% efficiency unless you choose a converter with higher rated current (maybe 8A or higher), which means higher cost.

    If they can accept lower efficiency (still >80%) considering low cost.

    [13-A]

    For TPS564252 of 1.8V/0.133A application. The same please let me know the cost competitivity first and to be determined whether they’re suitable solutions. Looks like TPS564252 is better TPS564257 of this application from simulation result. I believe it is because the loading is only 0.133A.

    The simulation result of TPS564252, efficiency is around or above 90% overall and it’s Vout tolerance is 1.13%.

    The simulation result of TPS564257, efficiency is bad that even barely reach 60% while heavy load. Vout tolerance is the same 1.13%.

    Many Thanks,

    Jimmy

  • 0 in reply to Jimmy Lai
    TI__Expert 7320 points

    Hi Jimmy,

    Good to know >90% efficiency is no longer a hard requirement and thanks for your efforts.

    I'm slightly confused about the application, is that 1.8V/0.133A or 1.8V/1.33A? Do our customer still have 1.2V/2.284A application? I didn't see you mentioned this one.

    1. Regarding you questions, about the cost, TPS564252 and TPS564257 are not much difference while they're both cheaper than TPS54424.

    2. The efficiency gap may be due to the boundary of DCM and CCM.

    Jimmy Lai said:
    The simulation result of TPS564257, efficiency is bad that even barely reach 60% while heavy load. Vout tolerance is the same 1.13%.

    3. Below is the efficiency plot which reaches 90% under ~0.7A but not 60%.