• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Subscribers 66 subscribers
  • Views 772 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.

TPS54332: some questions

Hirotaka Matsumoto
Guru 27585 points
Part Number: TPS54332

Hi all

Would you mind if we ask TPS54332?

Please refer to the attachment file.
And could you give us the reply?
1185.20170418_TPS54332_Test Circuit.pdf

Kind regards,

Hirotaka Matsumoto

  • 0
    Expert 1545 points
    I am not an expert on the TPS54332 but have worked on other switchers.

    I am guessing your load started using lower current, and that caused your voltage to increase, as we see happened in the Green Vsense scope reading. The only way to lower the voltage is to stop switching and let the load bring it down. When it got low enough it started switching, but the voltage went high again, so it stopped switching again.

    I would have expected it to drop to the same level before it started again. But it did not, it started and maintained the voltage, so it kept switching until the voltage got too high again and it had to stop to shed the extra voltage.

    If I had to guess, it is operating as it should. (They call it Eco-mode where they skip switching.) I will bet if you added a resistor to ground to increase the load a little you would not see it, because you always have a load.

    I think this is "issue" is just because you have a very efficient circuit. It is not a problem. I would be happy.
  • 0 in reply to Kipton Moravec
    Guru 27585 points

    Kipton san

    Thank you for your reply.

    You added a resistor to ground to increase the load a little you would not see it, because you always have a load.
    ->As you mentioned, the problem resolved, thanks.

    We would like to confirm several points;

    <Point1>
    Between 0C and -10C, in case of -10C, the problem often occurs.
    This problem depends on load, otherwise in case of -10C, does the load decrease?
    (Or, internal osillator capacitance decreses or inductance decrease??)

    <Point2>
    And the datasheet shows ECO-mode as follows;
    "When the device is in Eco-Mode, the COMP pin voltage is clamped at 0.5 V internally which prevents the high-side integrated MOSFET from switching.
    The peak inductor current must rise above 160 mA for the COMP pin voltage to rise above 0.5 V and exit Eco-Mode."
    ->When the peak inductor current is over 160mA, the device exits Eco-Mode.
        So, during no switching operation, does it mean that the peak inductor current is less than 160mA?

    We appreciate your help always.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Intellectual 2790 points

    Hirotaka san,

    This should be caused by insufficient voltage on BOOT capacitor. A bit little load will make the frequency a bit higher in ECO mode, witch means BOOT cap will be refreshed more frequently, so this issue can be solved by a bit little dead load.

    Higher temperature will cause higher leakage current of the schottky diode, which is equivalent to a dead load, also will help refresh the BOOT cap.

  • 0 in reply to Hirotaka Matsumoto
    TI__Expert 5745 points

    Hi：

    Refer the document to improve low dropout operation with the non-synchronous converter in light load. www.ti.com/.../slva547a.pdf

  • 0 in reply to Vental Mao
    Guru 27585 points

    Vental san, Luke san

    Thank you very much for your reply!
    We would like to confirm several points.

    <Confirmation1>
    Boot UVLO on the datasheet P10 and, on the document which shows www.ti.com/.../slva547a.pdf, it shows "the BOOT to PH voltage falls below 2.1 V, forcing the high-side switch off."
    ->We guess that Boot UVLO value is typ2.1V. So is there some tolerance depending on the devices?(the value of some device is 2.2V,,,)

    <Confirmation2>
    In case of Vin=5.3V, Vout=3.3V and noload, the device operates switching normally.
    According to increasing of Vin from 5.0V to 5.3V, Boot voltage increases.
    As the result, the BOOT to PH voltage is over 2.1 V.
    Is our recognition correct? 

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    Guru 27585 points

    Vental san, Luke san

    If you have some comments, could you let us know?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Expert 4035 points

    Hi Hirotaka,

    As for confirmation 1; yes, there is some tolerance depending on different temp among the devices. I have a not very clear picture showing that tolerance, hope you could see clearly.

    As for confirmation 2; When Vin>6V, The max boot voltage equals to 6V, when Vin<6V, the max boot voltage is following Vin (has some voltage drop). To work normally, the boot voltage must be higher than 2.1V(typical value)

    BRs,

    Ryan Hu

  • 0 in reply to Ryan Hu (BSR-MV)
    Guru 27585 points

    Ryan san

    Thank you for your reply!
    OK, we got it.

    Kind regards,

    Hirotaka Matsumoto