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LM5104: A question about LM5104, LM5101

Erwin Xie
Intellectual 935 points
Part Number: LM5104
Other Parts Discussed in Thread: LM5101

hi, 

My customer is developing a module, and they found the Negative voltage on drive’s input and output pin were higher than -0.3V, is there any risks for this application?

Here are the Schematic and waveforms:

Waveform on HB pin of LM5104:

CH3 MAX is 12.3V

CH3 MIN is -2.2V

Waveform on HO/LO pin of LM5101:

CH3 MAX is 12.2V

CH3 MIN is -4.49V

  • 0
    TI__Mastermind 20950 points

    Hello Erwin,

    Thank you for supporting the LM5101 and LM5104 drivers in this application. I am an applications engineer with HPD and will work to answer your questions.

    First I have a question about the 1st plot that is shown to be the HB pin on the LM5104. In the schematic it shows that HB is connected to VDD so I would expect HB to be a DC voltage. Can you confirm if this is HB or is it HO, LO, HI or LI?

    If the 1st plot is an input or output pin, the negative voltage is less than 2ns which is not a concern for a couple of reasons. 1) It is difficult to measure switching waveforms without some amount of high frequency ringing or spikes. 2) the time is so short that there is very little energy in the negative spike, if the plot is accurate.

    On the second plot of the LM5101 HO pin. Firstly the waveform indicates some continued ringing which indicates this is high frequency ringing from the probe setup. Also in this case the time duration of the negative spike in question is very short, which would have very little energy associated and very little time to cause any significant conduction of the internal device body diode.

    The third plot which I assume I is the LM5101 LO pin. The negative amplitude is below -0.3V for ~16ns based on the plot with a negative peak of ~-900mV. In this case the negative amplitude is modest and the duration is short also. There will not be enough time to generate any significant current in the LM5101 internal device body diode in this case either.

    Please confirm if this answers your questions by selecting the green button, this will help us.

    Regards,

    Richard Herring