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LM5113: device failure when a load short circuit happens

Mattia Di Noto
Prodigy 10 points
Part Number: LM5113
Other Parts Discussed in Thread: LMG1205,

Hi,

I'm working with the LM5113 connected as below:

I'm using the high side driving section to drive a E-GaN to push current to a load.

I have no problem in driving a resistive load, i tried to drive with 18 A current peaks with no problems.

I have to test the response to the load short circuit, but when i connect a short circuit instead of a resistance, i experience a LM5113 failure. After this failure i measure the impedence beetween HS and HOL (that is connected to HOH in my circuit) pins of 2 ohm instead of 100kohms in normal condition.

Could you tell me what is going in failure? Have you some idea to let the LM5113 survive to load short circuits?

Thank you, regards
Mattia

  • 0
    TI__Genius 9301 points

    Hi,

    We'd like to get some more information about your test:

    What is the state of your input signal at HI pin when the failure occurs?

    Does the issue happen right away at startup or does it happen after HI signal has switched a few times? 

    Did the FET fail/got damaged too?

    Best regards,

    Leslie

  • 0 in reply to Leslie Marquez
    Prodigy 10 points

    Hi,

    the failure occurs when i switch on the TTL input signal at HI pin. So i think the failure occurs during the HIGH state of the input signal at HI pin.

    The issue happens immediately, so i think at the first LOW to HIGH transition of the input signal.

    After the replacement of the damaged LM5113 the circuit returns to work, so the FET is still OK.

    Here a more detailed description of the cirucit:



    Can the 10 nF capacitor cause the failure?

  • 0 in reply to Mattia Di Noto
    TI__Genius 9301 points

    Hi Mattia, 

    Thank you for providing more details. Since the FET is not failing, could you please confirm whether the issue occurs with HS tied to the driver's GND and removing the 2 Ohm gate resistor? This would be a sanity check of the driver and if that works correctly then we can trace it to the external components.

    Regards,

    Leslie

  • 0 in reply to Leslie Marquez
    Prodigy 10 points

    Hi, 

    So if i open the connection from HOH/HOL to Gate removing 2ohm resistor and connect HS to driver GND i can check if the problem is inside the driver or outside, caused by the components connected to him. Ok, i will check this condition.


    During my last debug section i placed a zener diode in parallel to 470nF cap between HB and HS as described below:

    This solution is OK in the case in which i make the short circuit with a wire AFTER turning on the TTL input signal. In fact if i turn on with the short already done i see the same failure of the LM5113 again.

    Another question: is there any difference between LM5113 (that is in NRND) and LM5113-Q1? Do you think that the -Q1 version could survive to this short circuit situation? The LMG1205 (i see is the suggested alternative to LM5113) could survive to this situation of short circuit?

  • 0 in reply to Mattia Di Noto
    TI__Genius 9301 points

    Hi Mattia, 

    Thanks for checking under the conditions explained. Let us know what you find out. 

    Regarding the LM5113 and LM5113-Q1, LM5113-Q1 has the same functionality as LM5113 but LM5113-Q1 is qualified for automotive applications. Regarding the LMG1205 vs LM5113, please see this e2e thread 

    There was an issue with LM5113 for input pulse widths around 2.2ns (below the recommended 10ns). This was fixed on LMG1205. If you are using pulse widths in the 2-3ns range we can look into this route, otherwise let's try to identify the component that it's causing the failure by running the test with the conditions suggested.

    Regards,

    Leslie

  • 0 in reply to Leslie Marquez
    Prodigy 10 points

    Hi,

    i did this tests on the circuit:

    1) Short circuit without the 2 ohm resistor, this didn't cause the failure on the LM5113

    2) Short circuit with the 2ohm resistor and without the 10 nF capacitor, this caused the faiulre on LM5113

    The only solution that let LM5113 survive is the 5.1 V zener diode as in the last image posted.

    Regards,
    Mattia

  • 0 in reply to Mattia Di Noto
    TI__Genius 9301 points

    Hi Mattia, 

    Thank you for sharing your findings. I'm glad you were able to find a solution by adding the zener diode to clamp the voltage. 

    From you description that after the failure the impedance between HS and HOL is 2 ohm, the issue could be related to reverse current getting coupled to HOL pin and causing the internal pull down circuit to get damaged when the gate is getting turned off. It would be interesting to also measure HB to HOH to know if the internal pullup circuit is also getting managed. If you look at the voltage across the external gate resistor during the failure you could see how much current the gate is seeing and if it's exceeding the driver's capability. 

    Since clamping the HB to HS voltage solves the issue, it would also be interesting to probe HB to HS voltage during the failure to see if it's exceeding the recommended operating conditions. 

    Best regards,

    Leslie