• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 65 subscribers
  • Views 408 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

LM5146: Schematics Review

Desireddy Teja Reddy
Intellectual 590 points
Part Number: LM5146
Other Parts Discussed in Thread: LM76005, CSD19502Q5B, CSD19534Q5A

Hi Team,

We are using the LM5146RGYR Switcher part in our schematics. We had used in couple of instances, I had attached the schematic Images below, Kindly review the schematics and share your valuable feedback with us.

Thanks and Regards

- Teja

  • 0
    TI__Mastermind 22299 points

    Hi Desireddy.

    Any reason why you put ferrite bead on the VIN of the LM5146?

    I think this is unnecessary and should be removed.

    Please fill out and attach two design calculators spreadsheets so we can check your design: https://www.ti.com/tool/LM5146DESIGN-CALC 

    -Orlando

  • 0 in reply to Orlando Murray
    Intellectual 590 points

    Hi Orlando,

    Thanks for your valuable feedback. The ferrite bead we are using is for the filtering purpose. i filled the two design calculators and i had attached below. please share your feedback on them. I have some concerns we are using Under voltage lock out resistors for both the designs and the Current limiting Resistor and capacitor with these two scenarios i am unable to add the respective values over the design calculator excels.

    I had mentioned those values below.

    Design V out = 5V

    UVLO

    Ruv1 : 237K

    Ruv2 : 6.04K which acts as a voltage divider and gives the output as 1.2V approx.

    ILIM

    Rilim : 2.2K

    Cs : 3.9Pf

    Design V out = 5.5V

    UVLO

    Ruv1 : 237K

    Ruv2 : 6.04K which acts as a voltage divider and gives the output as 1.2V approx.

    ILIM

    Rilim : 3.4K

    Cs : 2Pf

    Note: All the values are referred from the webench design.

    Please find the above mentioned values and the attached Design calculated excel and share your feedback.

    Thanks and regards\

    - Teja

    LM5146-48-5.5V.xlsm

    LM5146-48-5.V.xlsm

  • 0 in reply to Desireddy Teja Reddy
    TI__Guru 51631 points

    Hi Teja

    Orlando is out of office now. He will reply on Friday.

    -EL

  • 0 in reply to EricLee
    Intellectual 590 points

    Hi Team,

    Gentle Reminder. Please share the feedback for the schematics.

    Thanks and regards,

    - Teja

  • 0 in reply to Desireddy Teja Reddy
    TI__Mastermind 22299 points

    Hi Teja,

    What is the reason you want to use a controller for 4A?

    You can have a much easier 5.5V/4A design with LM76005. 

    The high-side FET CSD19502Q5B is not suitable as the losses are very high this causes lowered efficiency.

    You dont need a low RDSON for high-side fet as the duty cycle is very small (10%) so the high-side FET conduction time is very low. 

    You would be better using a lower QG FET for highside, like CSD19534Q5A, lowered Qg will reduce switching losses.

    Your current limit setpoint of 10A should be 30-40% higher than the output current, use 14A. Looks like the ILIM resistor on your schematic is 681Ω and you should be using 232Ω for that low-side FET. Note this ILIM resistor depends on RDSON of the low-side FET.

    The quickstart calculator will calculate values based on your required turn-on and turn-off voltage. With your current resistor values looks like turn-on voltage is 48V and turn-off voltage is 45.6V?? Please confirm.

    The compensation values are not very good. Please use the recommended values from the quickstart and ensure your phase margin is greater than 45degrees, ideally 60 degrees or larger. 

    Hope this helps,

    -Orlando

    LM5146-48-5.V (1).xlsm