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UCC23513: Gate Driver getting hot and eventually failing

CHRISTOPHER YECKEL
Prodigy 155 points
Part Number: UCC23513

Hello,

I am driving the output of the UCC23513DWY with ±12V from a ±12V power supply TMA 0512D. They are driving the gate of a mosfet IXFN360N, which is where it gets its return back to the power supply common. These are isolate supplies (6) and they drive (6) series mosfets. 

I am running ±12V on the output with respect to common, which is not covered in the datasheet, but I don't see any reason why it wouldn't work.  

Works fine most of the time. Every now and again the device gets really hot and burns up, for apparently no reason. 

I attached a snippet of the circuit. I can send more if needed. Basically the mosfet is in parallel with a 0.05ohm resistor, the function of the circuit is to either drive current through the mosfet or the resistor to vary the voltage drop across the stage. 

They seem to fail on their output where the VCC and VEE short together. I used to run with a ±15V supply which I thought might be too close to the VCC max (33V) so I reduced to ±12V but still having the issue. 

Let me know your thoughts. I am not even running and current through the 0.025ohm resistor at this point, so there are not isolation concerns. 

PS0 PS1 PS2 are isolated ±12V supplies. I am not switching the UCC23513DWY at this time and driving a constant 8.5mA into the input diode. 

There is no voltage across the 10 ohm gate resistor, so there is no excess gate current draw. 

Something is certainly dragging my supply voltage down a bit, that seems to be what is heating U1. >60C in 5 min. I have not let the current one burn up yet, but is might already have a problem? 

I can send any more information if needed. I feel like this is enough information to get started? 

-Chris 

  • 0
    TI__Mastermind 22746 points

    Hi Chris,

    What does your power supply decoupling for the output stage look like? You might have voltage transients above the 33V abs max. It looks like you have only a 22uF capacitor to each rail, but usually we use an 100nF directly next to and across the supply pins to filter out high frequency overvoltage. You could use a clamping TVS diode across the rails too just to be safe.

    I have had a similar problem to this when the root cause was a lot of switch node resonance, but only for non-isolated drivers. Do you have any voltage measurements of the switch node or gate voltage?

    Best regards,

    Sean

  • 0 in reply to Sean Cashin
    Prodigy 155 points

    Hello Sean, 

    I have 13V zeners on each rail of the power supply to common. I am also not switching at all (have not gotten there yet). Also note that the device fails short VCC to VEE only after it has burned up. So right now, when I turn it on for a minute or two to take some measurements, it is still functioning...

    Clearly the gate driver in question is pulling down the voltage slightly when compared to the 5 other drivers. There is energy going into the driver from VCC/VEE that is not making it out of the device. 

    -Chris  

  • 0 in reply to CHRISTOPHER YECKEL
    TI__Mastermind 22746 points

    No switching yet? Then this should be an easy problem to diagnose with DC measurements. There is something that happens to the driver that causes it to start taking lots of supply current, and eventually shorts the supplies. We just need to figure out what it could be. The options are supply overvoltage, output overvoltage, or output overcurrent.

    If you replace that driver with a new one, will that same driver always fail again or could different ones fail instead?

    What are D22 and is it D37?  Are these diode structures dumping lots of direct current into the driver output The outputs are really only meant to sustain high transient currents, and will burn up if run with a high DC load. You said that there was no voltage across the gate resistor, but is that always true?

    Is the IXFN360 damaged in any way? if it is easy to remove, does a new driver fail when the switch is not there?

    Best regards,

    Sean

  • 0 in reply to Sean Cashin
    Prodigy 155 points

    Hello Sean, 

    Sorry for the delay I was testing some stuff. To answer your questions:

    The driver failure seems random, but typically it is one closer to the top (of the schematic). 

    D22 and D37 are TVS diodes (bidirectional zener). The gate/source diode is 15V and gate/drain diode is over 30V. 

    Currently I have the card removed from the MOSFET board. That is, the mosfets are not in the circuit. I have replaced the gate driver that was getting hot with a new gate driver and it is now also getting hot. I don't think that the device itself has failed, but on the way to failure if I were to allow it to continue to heat.

    Put the board on my lab supply and it is drawing ~3W for the 6 gate drivers.  

    DC/DC converters running at 80% efficiency that would mean the 6 gate drivers are pulling about 2.4W or 400mW/device. I don't believe they are all pulling the same power, but I have no good way to isolate them. I think the hotter one is pulling over a watt. It has to be spending it internally too... 

    I guess my next step is to start pulling all the devices on the output (steering diodes, TVS diodes) and see if that is where the current it going? 

    Without the mosfets... what the heck? 

    Note that I am still in a DC case. No switching. 

    I would like to send the whole schematic... but I can't post it in its entirety on here do to proprietary concerns, but if yo uneed more info let me know. 

    Let me know your thoughts, 

    -Chris 

  • 0 in reply to CHRISTOPHER YECKEL
    Prodigy 155 points

    ...also note that I added  ceramic 50V 100nF decoupling caps VCC/VEE. 

  • 0 in reply to CHRISTOPHER YECKEL
    TI__Mastermind 22746 points

    Hi Christopher,

    When you replaced the hot driver and turned on the board, was the new one cool for a while, or did it immediately start drawing lots of power? I think the next step is to measure the DC voltage at each pin of the driver? With no switching, something is probably out of spec at DC, such as the power supply voltage or the output current. 

    If you want to confidentially share your schematics, you can ask a new question using the -INTERNAL forum.

    Best regards,

    Sean