Hi team,
I'm posting this question on my customer's behalf. I will share corresponding schematics privately. The question and background is below.
I found abnormal waveforms for UC2825AQDWRQ1. Please help me to find the root cause of the PWM stopping problem and the solution to is
The IC pin signals are normal:
1. SS (purple) keeps high 5V
2. EAO (Light Blue) keeps constant
3. The CT (Deep Blue) signal is clean, and the peak is about 1V (the trip level is 2V)
4. Iout (Green) is used to trigger the event.
Under the normal external signals. CT drops to zero at the peak of about 0.8V! This is strange. The overcurrent setup is 2V with the CT output devider. The shut off is not only far below the threshold but also below its normal running peak voltage (1V). I feel the external EMI noise penetrates the chip and caused the chip malfunction.
There is solid GND plane beneath the chip, but the 2-OZ copper of the plane is not good enough to resist the strong external EMI. Out external taping just enhances the shielding of the internal GND plane.
Thank you,
Lauren
