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TPS54616: Unable to generate 3V3 power supply with DataSheet configuration

user6174539
Prodigy 10 points
Part Number: TPS54616
Other Parts Discussed in Thread: TPS54678

Hi all,

In my design, I need to generate a 3V3 power supply from 5V voltage. As the devices in the design request a current greater than 2A I decided to use the TPS54616, which provides 3V3 and at least 6A of current.

The figure shows my configuration, as shown in the datasheet.

The problem

When I connect my 5V power supply to the circuit, I only get 6mV at the output pin (PH) with this configuration.

The values of the components are in the range of values recommended by the datasheet:

  • C19 (from BOOT to the output pin PH) must be in 0.022uF - 0.1uF range, so I decided to put 0.047uF.

These were my steps attempting to solve this problem:

  1. I have changed the value of C19 to other values (in the range above) --> still not working.
  2. Remove R72 from SS/ENA pin to 5Vdc. This will leave the SS/ENA pin open --> still not working.
  3. Instead of R72, I have used a slow-start capacitor, but nothing changes --> still not working.
  4. If I remove C19 (BOOT capacitor) from the circuit, I get 3V3 volts at the output pin --> seems to be working.

So if R72 and C19 are removed from the circuit, I get the desired voltage at the output.

  • Why is this happening? Datasheet says that a capacitor needs to be connected between BOOT and PH pins.
  • In a particular situation, the inductor (output filter) started to make noise, and after 1-2 seconds my power supply stopped feeding the circuit (as a protection).
  • Which are the correct values for the components in the case of TPS54616?
  • What is the correct schematic to make the circuit work?

Kind Regards

Salvador

  • 0
    TI__Genius 10860 points

    Hi Salvador,

    thanks for your detailed description of your problem.

    To answer your questions I will need to go through your schematic in a bit more detailed, meanwhile I recommend for you to go through the Designing with the TPS54611 Through TPS54616 Synchronous Buck Regulators Application Report for details on the correct selection of passive values. This should already answer your question 3 and 4. Please also be aware of the Layout recommendations in the datasheet, especially with regards to avoiding long traces between pins and passives.

    Could you comment if your solution is including Css (without R72) and removed C19 or without Css, without R72 and without C19?

    Please also note that the TPS54678 is suggested for new designs as it is a newer 6V, 6A step-down converter with better performance and more features.

    Best regards,

    Britta

  • 0 in reply to Britta Ruelander
    TI__Genius 10860 points

    Hi Salvador,

    as I didn't hear back from you since my last post I assume it helped solving your problems.

    Note that I will close this thread now for inactivity.

    Please feel free to open a new thread in the future in case we can support you with anything.

    Thanks and best regards,

    Britta