UCC21710QDWEVM-025: Output switching waveforms test

a_kanezaki

When the input and output switching waveforms test was performed with the instruction on https://www.ti.com/lit/ug/sluubx2b/sluubx2b.pdf?ts=1680578620878&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FUCC21710QDWEVM-025, LED D10 becomes dark, but LED D11 is still "Light" when the function generator is turned on, and there is no output switching. How can I check the issue on the board? Before that testing, it was confirmed that power up and bias supply voltages test is normal.

Thank you for your support in advance.

over 2 years ago

0 Nancy Hidalgo over 2 years ago

TI__Expert 3760 points

Hi,

If D10 goes dark this means that the FLT pin is triggering (it is an active LOW pin). The FLT pin goes low when there is a overcurrent or short circuit event (signaled by the OC pin going over the .7V threshold voltage). When this happens, the output is also pulled low. This would explain the behavior you're observing. I would recommend taking a look at the voltage at the OC pin to determine what could be causing it to trigger the overcurrent protection behavior.

Best,

Nancy

0 a_kanezaki over 2 years ago in reply to Nancy Hidalgo

Prodigy 20 points

Thank you for your reply. It was confirmed that over 0.7V is observed at OC pin when FG is turned on. What kind of root cause can be estimated? Any components on the board are not changed after delivery.

0 Nancy Hidalgo over 2 years ago

TI__Expert 3760 points

Hi,

Could you share a bit more about your testing setup? What do you have connected to the CS, GATE, and other output connections? Alternatively, a quick workaround would be to short the OC pin (TP14) to COM (TP11).

Best,

Nancy

0 a_kanezaki over 2 years ago in reply to Nancy Hidalgo

Prodigy 20 points

Hi, thank you for your confirm. I am just following the section 2.2.2 of UCC217xx Family Driving and Protecting SiC and IGBT Power Modules and Transistor (Rev. B). So there are no output connections except for the initial components on the board. Is it necessary to connect additional load to the output?

+1 Nancy Hidalgo over 2 years ago

TI__Expert 3760 points

Hi,

I see. You do not need to have a load connected since you have that load capacitance on the board natively, but it may be useful later on to test your system. However, to prevent the OC from triggering you will need to short the OC pin to ground to see the output switching. Let me know if you run into additional issues.

Best,

Nancy

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UCC21710QDWEVM-025: Output switching waveforms test