• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 480 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

Has anyone successfully used the TPS54336 to make a constant current source?

Malcolm McClure
Prodigy 140 points
Other Parts Discussed in Thread: TPS5160

Has anyone successfully used the TPS54336 to make a current source?  I have built up the attached circuit but it refuses to work properly.  If I run it as shown (i.e. with C4 = 1uF), it produces close to the predicted current, but the switching frequency is only about 22kHz.  If I use a value of 250uF for C4, the switching frequency is correct, but I only get brief bursts of current.  The burst rate suggests that I am triggering the hiccup mode.

Current Source.pdf

  • 0
    TI__Intellectual 925 points

    Hi Malcom,

    Here is what I found:

    1. U1 is supposed to switch at 340kHz, which should be a maximum 3us period at 100% duty.
      U1 is staying on for 12us, so something is wrong there, perhaps damage.

    2. The FB pin is being driven to 2.5V.
      The TPS54336 has OV overvoltage shutdown at VREF +6% (pg.9 of Data sheet)
      You can see this on the picture below:

    3. Also, we recommend using soft start (Pin 8) on TPS54336 (pg.13 of data sheet)

    4. There is a white paper (SLVA374) where TPS5160 (a very similar part) as used a current source. This is a very common method for driving LED’s, we have several designs.

       

    5. After sifting through several reference designs, I couldn’t really have a good example of what you are trying to do. The closest is the MSP 430 design (SLAA287) there they are using a discrete solution, rather than a buck converter. This paper might also be of interest.

    At this stage I highly recommend using one of our BQ series of battery charger ICs for what you are trying to achieve.