• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 62 subscribers
  • Views 167 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.

TPSM365R6: TPSM365R6V3RDNR burned at power up

Janez Jazbar
Prodigy 10 points

Part Number: TPSM365R6

Hi,

 

Part (TPSM365R6V3RDNR) is damaged as soon it is connected to the input supply voltage (there is minimum load on the output +3V3 side).

Some more tests were done and another device was damaged when connecting 40V to the input (first damaged part was with 48V).

We also use 12V and 24V supplies and with theese we have no problems.

 

Additionaly, if we use input voltage >40V, part is never damaged if we connect the part to the power supply and the power supply has approx. the following

voltage shape at start. We tested power up sequence for more than 100x (all good).

 

But if first turn on the power supply and then connect the part to for example 40V,

That the voltage input was put to part without any rise time, then the part was immediatelly damaged. (smoke came out)

 

Schematics of our circuit:

 

PCB layout:

 

 

If you can check and suggest a solution to the problem.

Thanks.

 

Best regards,

Janez

  • 0
    TI__Genius 15550 points

    Hi Janez,

    This usually happens when ringing arises at the input and crosses the maximum rating of device. With a slower rise, the ringing would be less severe, which could be why there is no damage in that case.

    You would need a high ESR electrolytic cap or a TVS diode ( Vclamp < 70V) at the input of the device to protect against this.

    Regards,

    Niranjan

  • 0 in reply to Niranjan Nair
    Prodigy 10 points

    Hi Niranjar,

    Could you provide min. specs for the input capacitor - min capacitance?
    So, in your opinion, MLCC with low ESR is not OK even if we place more in parallel, e.g., some 22uF 100V MLCC capacitors.
    Because reading the datasheet, there is no electrolytic capacitor (with high ESR) specified or required.

    In the meantime:

    I have already tried with the TVS diode SMAJ45CA alone, but I still got burned part.
    So clamping at ca. 70V did not help.

    If I place a 10uF 63V electrolytic capacitor alone, for now, I can say it helps and solves the problem. 

    Thanks for the answer.

    Best regards,
    Janez

  • 0 in reply to Janez Jazbar
    TI__Genius 15550 points

    Hi Janez,

    The electrolytic cap is not necessary for the device to function, hence why it is not mentioned in the datasheet. However, in certain cases, especially with long input traces, high parasitics or fast slew rates, the input tends to ring. The electrolytic cap is needed to damp out this ringing. 

    I would not recommend placing the electrolytic capacitor alone though. It is not very effective at filtering high frequencies or providing charge during fast transients. My suggestion is to keep the 2.2 uF + 100n and add the high ESR cap in parallel with this. This way the ceramic caps can take care of high frequency noise/transients and electrolytic cap will damp out the lower frequency ringing.

    Also, the TVS diode SMAJ45CA has a Vclamp(max) of 72.7V. You would need one with Vclamp < 70V. This could be why it damaged still.

    Regards,

    Niranjan

  • 0 in reply to Niranjan Nair
    Prodigy 10 points

    Hi Niranjar,

    Thanks for the answer and suggestions.
    Will try to take that into account.

    Best regards,
    Janez