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UCC14240-Q1: IC overheating

Matteo Telli
Prodigy 20 points

Part Number: UCC14240-Q1
Other Parts Discussed in Thread: UCC15241-Q1

Tool/software:

Good morning, 


I am using UCC14240QDWNRQ1 to create a dual output voltage of +20V and -4V to drive MOSFETs at 40kHz. I have used the excel calculation sheet V6 to determine the components values without realizing that there was a new version available (V8). 
The IC is working and driving the MOSFETs properly, but its temperature is alarming high. In air, without MOSFETs being connected, the IC is reaching an external case temperature of 78°C. I have seven of these power supply per board, but not all of them reach this temperature. Some of them are running at around 55°C. Temperature is still high, but not as high.

Here is a screen shot of my schematic

Thank you for any assistance you can provide. 

  • 0
    TI__Mastermind 33135 points

    Below are my recommendations:

    1. RLIM resistor (R241) is very small. Internal RLIM switch resistance is ~50Ω and using R241=100Ω is causing tremendous internal power dissipation. This is the most likely cause of the high case temperature you are observing. Try changing from 100Ω to ~1-2kΩ and then also try the RDR configuration highlighted in the UCC14240 v.8 Excel Design Tool.
    2. Use Cout1b as described in the UCC14240 v.8 Excel Design Tool.
    3. Schematic seems to show a missing connection to net "SiC_Source" between C242, C244? Could be an error in the PDF/graphic conversion but check it to be sure. 
    4. C232-237, C173-174 should be physically placed at the gate driver
    5. C225, C229, C176 should be physically placed at the gate driver
    6. C230, C231 should be placed as close as possible to the UCC14240 VDD-VEE pins
    7. Try UCC15241-Q1 which is a higher power version of UCC14240. they are p22 and you can drop in UCC15241-Q1 to replace UCC14240-Q1. Try all the above recommendations first.

    Regards,

    Steve

  • 0 in reply to Steven Mappus1
    Prodigy 20 points

    Hello, 

    Thank you for the suggestions. A 1kΩ resistor fixed the issue.