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LMG1205:

user5062484
Prodigy 20 points
Part Number: LMG1205

we use the LMG1205 in our 84-50V buck converter as the GaN HEMTs driver, but it occurs some abnormal phenomena in the prototype test, as shown in the following figures: the HI/LI input of LMG1205 is normal (as shown in first figure), the LO is normal，but the HO output is abnormal.

Do you know potential reasons for the abnormal HO output of LMG1205？

  • 0
    TI__Genius 12990 points

    Hi User,

    thanks for reaching out on e2e about LMG1205, sorry to hear about the issue you are having with HO.

    Can you share LO and HO waveforms similar to how you have shown LI and HI waveforms?

    are you using a different GAN FET for the high-side than you are the low-side?

    can you confirm the voltage on VDD is 5V nominal? is another 100nF VDD cap placed as close as possible to the device?

    what Fsw? what application or EE is this for?

    thanks,

  • 0 in reply to Jeffrey Mueller
    Prodigy 20 points

    Thanks for your reply. Possibly because of the network reason, the HOLO waveform did not upload successfully. The HO-LO waveforms  are shown in the following.

    The high-side switch is EPC2033, low-side EPC2034. the voltage on VDD is 4.7V. 

    Looking forward to your reply.

  • 0 in reply to user5062484
    TI__Genius 12990 points

    Hi User, Thanks for the update,

    It seems that the HO out is stuck at 2.2V. Have you ever seen HO switching normally before? what were the operating conditions when HO was first seen abnormal?

    are you using a different duty cycle in your LO/HO waveform than you are with the LI/HI waveform?

    does HO ever change voltage from 2.2V? what is the HB-HS voltage?

    are you sure that HI is switching during this time?

    If so, the high-side output may be damaged. is the high-side FET operating ok?

    what dead-time are you using?

    in the LI waveform the fall time appears to be slow compared to HI fall time, is this intentional?

    Thanks,