My client is using an ON semi FDMT80080DC mosfet which advertises an Eas of 1734 mJ, and I would like to suggest the CSD19506, but its Eas is listed as 832 mJ
I understand from your video that other competitors use deceptively higher inductance (as does the FDMT fet) to inflate their Eas value...but how can I compare these two devices apples to apples? Can you help me understand the real value of the FDMT fet?
Thanks
Hello Jeffrey,
Thanks for the inquiry. TI tends to be fairly conservative with the avalanche current and energy specs published in our FET datasheets. A number of samples are tested to determine the measured capability with 0.1mH, 1mH and 10mH inductor values at 25°C and 125°C. The avalanche current is the average of the capability of the samples tested and derated. The avalanche energy is calculated as ½ x LI² where I is the derated average value of current. In the case of the CSD19506KCS, the datasheet current (129A at 25°C) has been derated to 65% of the measured capability and the energy is ½ x 0.1mH x 129A² = 832mJ. Since we do not publish specs with 1mH and 10mH, the plots in Figure 11 of the datasheet are an attempt to convey that data. I pulled up the data collected during product development. The derated average current with 1mH is 55.5A (derated to 65% of measured capability) and the calculated energy is 1538mJ. With 10mH it's 25.5A and 3264mJ. I took this data and created the scatter plot with smooth lines of EAS vs. L (log scale) and included a power trendline as shown below. I used the trendline equation to estimate EAS = 2230mJ with a 3mH inductor. Based on this, I believe the CSD19506KCS has as good or better avalanche capability than the competitor's part. I hope this helps. Let me know of you have any questions.
Best Regards,
John Wallace
TI FET Applications
