• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 261 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.

Original question:

TPS63000: TPS63000 feedback capacitor

TPS63000: TPS63000 feedback capacitor

Samuel Souza
Prodigy 10 points
Part Number: TPS63000

Tool/software:

Hi. I'm developing the power system for an IoT system, and I'm using the TPS63000 as the buck-boost converter for a 3V8 output. I've noticed some issues related to the feedback voltage divider. I'm using R1 of 680k and R2 of 100k, and when I bring my hand close, the IC heats up and makes a hissing noise. What could be causing this? Can anyone help me?

Attached is a portion of the TPS63000 datasheet:

  • 0
    TI__Guru 65310 points

    Hello Samuel,

    You mention you bring your hand close to the feedback divider. Does this mean you are touching the circuit with your finger? Please be aware that your body is a big parasitic resistance and capacitance. If you place this additional parasitic components somewhere to an electronic circuit, you can even damage it.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 10 points

    Yes, but I didn't express myself well. I went to measure the circuit voltages with the multimeter and noticed this.

    Is there any way to mitigate this issue? For example, I didn't place the Cff; could that help?"

  • 0 in reply to Samuel Souza
    TI__Guru 65310 points

    Hello Samuel,

    If you touch the FB node with a multimeter, the internal resistance of the multimeter will influence the FB node. You need to use a really high-impedance multimeter, otherwise it will influence the FB voltage. Be aware that the FB input is a high-impedance node that needs special attention.

    It is important that the FB resistors are very close to the IC and not close to the output capacitors for example.

    Any circuit change you are doing on FB will influence the transient responses of the circuit even when you are not measuring. So most important is first to make sure that the layout is good enough for the DC/DC converter.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 10 points

    Okay, if you can take a look at the layout, I can send it to you in private... What do you think?

  • 0 in reply to Samuel Souza
    TI__Guru 65310 points

    Hello Samuel,

    The expert of this device will be back middle of the week. Please expect an answer from him.

    What you could try is reducing the resistor divider by a factor of 10 and check if the problem is reduced.

    Best regards,
    Brigitte

  • 0 in reply to Samuel Souza
    TI__Mastermind 32350 points

    Hi  Samuel,

    If you still want a layout review from our side, you can send me a private message.

    Regards

    Tao