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TPS55288: Need help with the schematics generated by webench unable to get output

nrupavesh n
Prodigy 10 points
Part Number: TPS55288
  1. i had used a design from webench and i am unable to get the output 20-32V__20V3.25A.pdf

i am attaching the schematic downloaded from webench which i used to generate the pcb the output from the board is 1.4v where i am giving input of upto 30v and my desired output is 20v from the pcb.

please help me with this 

the observations are the en pin is high with 1.9v

the DR1H is showing 1.4v at resistor  R3

the DR1L is showing 0.0V at resistor R4

i need 20v output at the vout.

  • 0
    TI__Mastermind 27750 points

    Hi Nrupavesh,

    Thanks for reaching out. 

    May I know what is the application here? Why does the input voltage vary so much?

    Can you show your schematic and layout here?

    Please check if VCC voltage is correct, then I2C message can be sent to the internal register. And without I2C, the output of TPS55288 can't be enabled.

    BRs,

    Bryce

  • 0
    Prodigy 10 points
    The schematic that I've shown is from the web bench, and it's not showing any I2C lines connected.
    Please find the attached documents below.
    Regards,
    Nrupavesh.
  • 0 in reply to nrupavesh n
    TI__Mastermind 27750 points

    Hi Nrupavesh,

    I don't find the attached documents, can you upload it again?

    Do you use I2C to program TPS55288?

    BRs,

    Bryce

  • 0 in reply to Bryce Xun
    Prodigy 10 points

    Hi,

    I am attaching the schematic and webench generated report for reference in that no i2c lines are connected.

    please find them.7446.20-32V__20V3.25A.pdf

  • 0 in reply to nrupavesh n
    TI__Genius 14950 points

    Hi Nrupavesh,

    In some Webench simulation, the I2C function is not integrated and the schematic is for design reference. In real application, the SCL and SDA pin must be connected as our EVM board shows, otherwise the TPS55288 can not be enabled.

    Since you did not connect the I2C lines, does that mean you do not need I2C function? If so, you can change the TPS55288 to the TPS552882 directly in your PCB. Please let me know if you accept the solution and we  can do schematic and layout review for you.

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Prodigy 10 points

    Sure help me with this, first can you check schematics

  • 0 in reply to nrupavesh n
    TI__Genius 14950 points

    Hi Nrupavesh,

    Below is my feedback:

    1. Recommend to change R3 and R4 to 0.
    2. Add a 0402 0.1uF capacitor in Vin pin and put it as close as to the device.
    3. Recommend to change R2 to 200k. The current EN voltage is too close to threshold.
    4. Change R9 to 6.38k to get 20V output voltage.
    5. Add RC snubber in SW1 and SW2. Recommend 2.2ohm(1206 or 2*0805)+2.2nF at first. Do not let RC snubber in SW2 side unpopulated.
    6. Recommend to use 4.7uH inductor with Isat>6A.
    7. Recommend to add 1 0402 ceramic capacitor, one more 10uF ceramic capacitor and one more 47uF electrolytic capacitor in the output.
    8. Please provide the output capacitor part number(including added capacitor from suggestion 7) so that we can recommend compensation parameters.
    9. Please provide the layout file to review.

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Prodigy 10 points

    Please find the attached gerber

    my board is already fabricated one please verify this to make it workable

    LAP_CHG_GEB.zip

  • 0 in reply to nrupavesh n
    TI__Genius 14950 points

    Hi Nrupavesh,

    I cannot open the file. Please send the layout screenshot of each layer in form of PowerPoint or PDF.

    Have you try to change the device? Is the output normal now? Also with your current board please try to follow my advice above.

    Would you kindly let us know what is your application here?

    Regards,

    Mulin