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WEBENCH® Tools/TPS54308: Output Not Stable and No Current From IC

Bryan Legnini
Prodigy 90 points
Part Number: TPS54308
Other Parts Discussed in Thread: LMR16006,

Tool/software: WEBENCH® Design Tools

Hi I used Webench to simulate a circuit and seemed that it would work fine. We purchase the parts and after setting up the circuit I cannot get the proper voltage out. We designed it to work with 4.5-28VDC and output 3.3V

I am applying 8VDC to the circuit and the voltage jumps around between 2.5-3.6VDC, when a 250-500mA load is applied the voltage immediately drops to 0V. 

Can you see anything wrong with this circuit?

  • 0
    TI__Expert 5745 points

    Please upload your layout, and the waveform of the jump Vout.

    Check all the components are solder down well and no current limit in the input source.

  • 0
    TI__Expert 5745 points
    Hi
    It's will be set as Resolved if you have no more inquiry on this thread.
  • 0 in reply to Vental Mao
    Prodigy 90 points

    Hi All components are conntected properly and the supply source has an output current up to 5A.

    The circuit is built onto a breadboard for testing and the schematic was attached above. That is what the design gave me in the webench tool.

    My main concern is that the voltage does not stay at 3.3V steady and drops to 0 when a load is added.

  • 0 in reply to Bryan Legnini
    Prodigy 90 points

    I was able to get the output stable at 3.3V and outputting over 1A. Turns out the feedback resistor needed to be connected directly to GND pin or is did not operate properly.

    My issue now is that the output is not very clean. There seems to be a lot of noise on the output and increasing the input voltage increases the amount of noise.

    How can I prevent/reduce the noise on the output?

    Best Regards,

    Bryan

  • 0 in reply to Bryan Legnini
    TI__Expert 5745 points

    Hi

    You can't use the breadboard for the power circuit. Only the PCB can work well for power circuit,especially with the heavy load.

  • 0 in reply to Vental Mao
    Prodigy 90 points

    Yes I took the circuit off a breadboard and I placed this onto a PCB yesterday. After re routing the ground from the feedback divider its now working but I am now having these spike issues. With a load or without any load there is the same pulse shown in the last image. As the voltage input increases the spike peak increases.

    I am worried that this spike could do damage.

    Any suggestions to filter or prevent this?

  • 0 in reply to Bryan Legnini
    TI__Expert 5745 points

    what's the PCB you used? can you upload it, the poor layout also will have this issue.

  • 0 in reply to Vental Mao
    Prodigy 90 points

    I do not have a PCB created the circuit is soldered to a prototype PCB to see if it will work. I am trying to make sure this will work before spending the time and money on a PCB to be produced.

    I am working on this to replace our current setup which was using a LMR16006YQ3DDCRQ1 to provide 3.3V up to 600mA. My new requirements are 3.3V with up to 1A, When using the LMR16006 I was able to build it onto one of these protoboards without any issues the output is clean over all voltage levels and it continues to work today just fine. 

    PCB Layout cannot be the only solution to fix this......

    Can you recommend a better IC to replace the LMR16006YQ3DDCRQ1?

    The package can be different but need to try to keep the size the same.

    Thanks

  • 0 in reply to Bryan Legnini
    TI__Expert 5745 points

    OK, i get your point.I think this is the solder issue.

    So you solder down the 54308 to the PCB of 16006 and see the issue in the output ? This may cause this issue.

    you can see the waveform of Vin pin to check whether the Vin also have this issue.

    Try to apply for TPS54308 EVM in our web.  www.ti.com.cn/.../TPS54308EVM-876