• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 63 subscribers
  • Views 363 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.

TPS55289: Oscillation stops

user1881876
Prodigy 230 points
Part Number: TPS55289

Tool/software:

Hello

Please tell me.

I am currently making a charger using TPS55289.

Charging voltage 8.3V, charging current 3A

When the charging current drops below 300mA near full charge, it goes into burst mode.

Even though it is called burst mode, it oscillates for 10 seconds, then stops oscillating for 10 seconds, and repeats this.

The above phenomenon does not occur in the constant voltage mode of the electronic load.

What is the cause of this?

Is the protection circuit working?

Best regards

  • 0
    TI__Genius 14870 points

    Hi,

    Thank you for reaching out. Can you provide schematic to us so that we can check if circuit is well designed? 

    What is the input voltage range, output voltage range and output current range? What is the difference between your different load condition?

    Can you help provide waveforms of input voltage, output voltage, SW1 SW2, and inductor current?

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Prodigy 230 points

    Hello.

    I will answer the following.
    Vin = 11.5~12.5V
    The output voltage range is 5~8.3V since it is charging a 2-cell lithium-ion battery.
    The output current range is 0.1~3A.
    Since it is used as a charger, the load is basically a battery.
    The oscillation stops this time when it is close to full charge, when it switches from CC to CV and the current is limited.

    Please wait a moment to see the waveform.

    Are there any application examples such as chargers?
    I would like to use them as a reference if there are any.

    I would like to ask about PFM mode.
    Currently, I have selected PFM mode, but the oscillation frequency does not slow down under light loads.
    It is close to burst mode, is that correct?

    Best regards

    7536.CIRCUIT.pdf

  • 0 in reply to user1881876
    TI__Genius 14870 points

    Hi,

    I will wait for your waveforms. Besides what I have mentioned, it will be better to also have output current.

    May I know which net is connected to charge battery? What is the CDC pin external circuit for?

    I think the compensation parameters are not suitable. To quickly check if it is loop stability problem, change R35 to 5k to see if it is better. Please provide part number of C29-C31, C35 so that I can calculate suitable compensation for you.

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Prodigy 230 points

    Hello.

    I will send you the waveform.

    The battery is connected between pins 1 and 5 of J5.

    The external circuit of the CDC pin transmits the charging current to the CPU.

    I understand the compensation parameters.

    Currently, I am using the CALCULATION-TOOL to consider the attached constants.

    C29-31: GRM31CD71H106KE11L

    C36: PCV1H470MCL7GS

    I would like an answer to the PFM operation question I asked yesterday.

    Is it correct that the frequency will slow down?

    Currently, the oscillation frequency remains the same, but the rest period tends to become longer when the load becomes lighter.

    Best regards

    Waveform_20240606.pdfTPS55289-CALCULATION-TOOL-V1(20240605).xlsx

  • +1 in reply to user1881876
    TI__Genius 14870 points

    Hi,

    In PFM mode, with light load, device will switch several cycle and stop switching for a while. The lighter the load, the longer stop switching time. The first waveform of your attached file is a normal PFM performance. 

    user1881876 said:

    Is it correct that the frequency will slow down?

    Currently, the oscillation frequency remains the same, but the rest period tends to become longer when the load becomes lighter.

    This description is normal PFM mode behavior.

    But the second waveform looks strange since output current is oscillating. What load is consuming the current? Is there any control? Have you try to change R35 to 5k?

    About your description: "Even though it is called burst mode, it oscillates for 10 seconds, then stops oscillating for 10 seconds, and repeats this." Can you give me some waveform to explain it? Time scale should be longer.

    Regards,

    Mulin