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Part Number: CSD97394Q4M
I am using the CSD97394Q4M in an application to drive dc cooling fans according to the temperature on the inside of a large chassis. These parts worked famously on bench trials with a varying PWM signal and Vin voltages up to 25 volts, so I desgned it into a backplane to control the speed of the fans. The trouble came when I attempted to run the fully loaded backplane in the environmental oven up to 30°C. My log showed that the CSD97394Q4M failed at 28°. Looking for answers I found on the Absolute Maximum Ratings that showed Vsw to PGND to be 30V max. With 24V on Vin, there is some overshoot to above 30V for maybe 2nS. Next I tried lowering Vin. Even with lower Vin I still get failures when the temperature is elevated. What do you think the problem is and what can I do about this?
In reply to Brett Barr1:
The attached png scope_5.png shows what the waveforms looked like just as it was failing. The yellow trace is the PWM input, and the green trace is Vsw. Nothing out of the ordinary. "scope_4.png" was captured as an irregular waveform (took many captures to finally get this, and this is with a good scope ground). The strange thing is that the Vsw goes high before the clock pulse.
Also attached is the data log showing the exponential temperature rise when the failure was occurring.
Thank you for looking into this.
In reply to Paul Norton:
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