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WEBENCH® Tools/UCC21530-Q1: gate driver issue

D MISHRA
Intellectual 470 points
Part Number: UCC21530-Q1
Other Parts Discussed in Thread: UCC21530, UCC21520

Tool/software: WEBENCH® Design Tools

Hi,

I am using a UCC21530 driver for generating a gate pulse. At the input enable pin, I have given a 2.3V supply with a voltage divider from 5V input. But I am getting the gate output voltage as constant and negative, same as the Vsa and Vsb (Pin no 14,9).

All the input pins are correctly showing the expected voltage values including the pulse input. The output biasing supplies are also showing +15V and -5V at the desired pins. But the gate outputs at HO and LO are showing the fixed negative voltage of -5V. (Vsa and gate outputs aren't sorted) I am not able to find the reason. Please sort out the problem if possible. I like to mention that I am testing only the gate driver without any load or switch connection, only with two isolated biasing voltage supplies and some coupling capacitors.

Thank you for your valuable time.

  • 0
    TI__Guru**** 189399 points

    Hi,

    What voltage do you have VCCI tied to? Both pins 3, and 8 are connected to that voltage with respect to GND, right?

    Two possible causes are UVLO on either the primary side or secondary side. Either of these would force the outputs low.

    Can you send a schematic we can review for all the connections?

  • 0 in reply to Don Dapkus
    Intellectual 470 points

    Dear Dapkus,

    Thanks for your valuable input and timely reply.

    I have applied +5V at the input VCCI with pins 3 and 8 tied. I have used two Murata isolated power supplies of +15,-5 as secondary power supplies. The pulse inputs are from a 28379D EVM board. The detailed schematic, I have attached as the doc file.

    I would be thankful if you could help me to find out the reason for gate outputs which are of the 1031.Doc1.docxsame voltages as -5V.

  • 0 in reply to D MISHRA
    TI__Expert 4065 points

    Hi,

    Can you check the configuration of your EN pin? It should be pulled high for the driver to switch, but you have it in a configuration that might cause it to be low. Additionally I recommend adding a 100nF capacitor between the VDD to VSS pins of both channels. 

    Regards,

    Krystian

  • 0 in reply to Krystian Plaskota
    Intellectual 470 points

    Thanks, Krystian.

    Sorry for the delayed reply due to some unavoidable reasons. I have tried to redesign the PCB with EN pin directly from +5V supply. I found no improvement. All the input pins respond perfectly in presence of a pulse input. However, I found, a constant -5V at G-S output. Even I turn-off the pulse with output biasing supply ON, still the G-S output shows -5V. Is it a problem with driver?

    Please suggest me the solution, as I am stuck here for the last few days.

    Thank you for your valuable time.

  • 0 in reply to D MISHRA
    TI__Expert 4065 points

    Hi,

    Can you take a picture of your test setup and the scope shots showing the input/output and how you're probing it? I can assist better if I have more details on your layout and test setup.

    Thanks,

    Krystian

  • 0 in reply to Krystian Plaskota
    Intellectual 470 points

    Thank you for your response. I have enclosed herewith the measurement set-up and related waveforms. I would also like to mention that the oscilloscope used here is an isolated channel type.

    Thank you TI_q.docx

  • 0 in reply to D MISHRA
    Intellectual 470 points

    Dear K. Plaskota,

    Thank you again for your vital input and quick support. I am able to find the mistake from my side. There was no problem with the driver or design and it works nicely up to 75kHz frequency. But the vendor has provided UCC21520 instead of UCC21530, where EN pin logic is simply reverse. In the meantime, I have designed 2 PCBs, including so many logic in designing, to find the reason behind low output.

    Thanks a lot for your precious input about my queries.