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Original question:

LM5116: LM5116

LM5116: LM5116

user1260659
Prodigy 170 points
Part Number: LM5116

I am developing a DC DC controller with input voltage ranges from 13V to 90V with output voltage of 12V. I have configured the board for about 3A load current. (LM5116MHX/NOPB)

I developed around 5 boards for testing. My observations were as follows:

Board gave only 3.9V output What might be the fault in these boards? is there any other parameters that i should verify? I have almost implemented the same circuit as that of LM5116 evaluation board

We used MOSFET FDMS86200 and BSC350N20NSFD and Bourns PM2120-560K-RC

Regards

H.J.Hamsaraj

  • 0
    TI__Guru 73175 points
    Please provide your schematic and a view of your layout.
  • 0 in reply to user1260659
    Prodigy 170 points

    I am developing a DC DC controller with input voltage ranges from 13V to 90V with output voltage of 12V. I have configured the board for about 3A load current. (LM5116MHX/NOPB)

    I developed around 5 boards for testing. My observations were as follows:

    Board gave only 3.9V output What might be the fault in these boards? is there any other parameters that i should verify? I have almost implemented the same circuit as that of LM5116 evaluation board

    We used MOSFET FDMS86200 and BSC350N20NSFD and Bourns PM2120-560K-RC

    Regards

    H.J.Hamsaraj

  • 0 in reply to user1260659
    TI__Mastermind 40040 points

    Hello Hamsaraj,

    Suggest we first fix the schematic. 

    Please see attached Quick Start calculator, I have entered in your specification, please follow all suggestion there in, 

    Please implement in your board and also please update your schematic to suit.  

    E2E LM5116_quickstart.xls

    Also YOu need to make sure you are not violating the Toff min spec if you are trying to get the LM5116 to operate at Vin min.

    Suggest reviewing link below to make sure you are not violating any specifications in the LM5116 datasheet.

    Hope this helps?

    David.

  • 0 in reply to David Baba
    TI__Mastermind 40040 points

    Hello Hamsaraj,

    Sorry I forgot to post link regarding duty cycle max capability, if this is indeed your issue.

    Hope this helps?

    David.

  • 0 in reply to David Baba
    TI__Guru 73175 points
    I am closing tnis due to inactivity
  • 0 in reply to Frank De Stasi
    Prodigy 170 points
    My observations were as follows input voltage ranges from 13V to 90V with output voltage of 12V. I have configured the board for about 3A load current. (LM5116MHX/NOPB) Board gave only 3.9V output What might be the fault in these We used MOSFET FDMS86200 and BSC350N20NSFD and Bourns PM2120-560K-RC
    Regards
    H.J.Hamsaraj
  • 0 in reply to user1260659
    TI__Mastermind 40040 points

    Hello Hamsaraj,

    In general, a low Vout can be likely caused by the following.

    1. Current limit engaging.

    1a. Due to Noise on the current sense

    2.a Due to real current reading on the CS pin 

    2a1. Can be due to cross conduction (layout)

    2b. Due to wrong Rsense value for load current

    2c due to Too much slope compensation

    2. Instability

    2a due to wrong compensation values

    2b due to noise (Layout)

    2c due to input filter interaction (Input filter undamped)

    I believe we have discussed this design in the past?  Is this the same design?  If so, we had discussed that the likely cause was the layout.  I believed at the time the layout was not ideal. I had made recommendations for you to fix the layout because the layout as it was, could very well cause you performance problems. 

    Have you fixed the layout since then, following all the recommendations I had made?  If not, this is likely the cause of the issue.

    If you wish me to re review your layout you can email me at the same email address as before.

    David.Baba@ti.com

    Hope this helps?

    David.