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UCC14240-Q1: questions about the calculator tool, RLIM

Robert Finger
Genius 16212 points
Part Number: UCC14240-Q1
Other Parts Discussed in Thread: UCC5310

Team,

I have questions about the UCC14240-Q1 Calculator (Excel sheet):

  • As "User input" there are IQ_DRIVER_VDD and IQ_DRIVER_VEE. According to the UCC5310 data sheet, IQ_DRIVER_VDD = 1.8mA. But I can't find IQ_DRIVER_VEE in the datasheet and RLIM changes a lot with different values. What should be used for IQ_DRIVER_VEE?
  • When I get e.g. RLIM(MAX) = 4582 Ω as a result, which value should I use for RLIM? 4k, 4.5k? How much lower can/should I go?

Thanks!
  Robert

  • 0
    TI__Genius 13570 points

    Hi, Robert,

    Which calculator are you using? If you can share it, I may help to find out.

    Thanks,

    Sean

  • 0 in reply to Sean Xu
    TI__Genius 13570 points

    Hi, Robert,

    I got the spreadsheet. There are three versions of UCC5310 (SEM). For S.M versions, VEE is connected to GND2, and there is no negative voltage for VEE. You need use IQ_DRIVER_VEE = IQ_DRIVER_VDD =1.8mA. For the E version,  the D/S doesn't provide IQ_DRIVE_VEE. I think it will be similar to VDD quiescent current. For more details, you can contact HPD.

    For the second question, you can choose RLIM smaller than the calculated resistance for more margin, such as 3.3K for 30% margin.

    Regards,
    Sean

  • 0
    Prodigy 90 points

    in the page 16 of UCC14240-Q1 is the formula for RLIM calculation. i don't think that i can simply put the same value. using the excel file on the website, with my setting:

    if IQ_DRIVER_VEE =1mA;  IQ_DRIVER_VDD =1.8mA => RLIM = 4.495 KOhm

    if  IQ_DRIVER_VEE =1.8mA;  IQ_DRIVER_VDD =1.8mA => RLIM = 140.355 KOhm

    the difference is too much. which one is the correct answer?

    also a new question:

    which primary  values are good for R2 and R4? shall i start with 10kOhm or should it be more in the range of 50kOhm - 100KOhm. what will happen if i chose a very high resistor value?

    Best Regards

    Bahar

  • +1 in reply to toktam khani
    TI__Genius 13570 points

    Hi, Bahar,

    For the version of S and M, it is single output, you need use Single Output spreadsheet on the second page.  RLim > 1kohm. For the E version, I entered 1.8mA for both IQ_DRIVER_VEE and IQ_DRIVER_VDD, I got RLim = 5.1k. please double check your calculation.

    You can choose R2 and R4 more than 10k, which can reduce power losses. But I don't recommend to go too high, which brings up large filter on VDDFB and VEEFB, it can slow down the response.

    Thanks,
    Sean