I have designed a circuit using LTC7801 to output 12V and 20A at full load. However, the IC failed (BG and GND shorted) when output was just 12V, 3.8A. I am using AUIRF3710ZS MOSFETs in high side and low side for the application. The IC turns itself off when the output approaches 12V and 3.8A, probably due to overheating. The device datasheet however, mentions operation up to 20A. Can someone help me out with this? The schematic and values are as suggested in LTPowerCAD, for the said output.
Provided that you use the suggested schematic and components in LTPowerCAD, then the IC should not fail at 3.8A/12V output. The schematic provided in LTPowerCAD for LTC7801 is rated for 12V output and 10A load. If you are going to use it for 20A, then make sure that you adjust the rating of other components attached to the IC.
You can also try to use our evaluation kit for LTC7801 which is available in the link below. It can be used for an input voltage range of 16V to 100V with an output of 12V/10A.
This is generally caused by the BG ringing above and or below the abs max of the part due to gate trace inductance and Mosfet capacitance. The solution is to place a 1nF cap at the IC from BG to GND and or to reduce trace inductance in the layout.
Thanks Seth and Gonzales. I changed the layout of my PCB with some help from a professional from ADI India. Now it is working fine, even at 12V, 20A output. I guess the problem was the trace inductance of the BG & TG traces, as pointed out rightly by Seth.