Original question:
Dear expert,
I have some question during my design with webench tool.
1. I would like to design a 42Vin to 12Vout@20A solution, but webench designer is failed.
Looks like webench designer use Rds_on sensing cause this current limit issue. Can I design my system with external Rsense?
2. What is the maximum soft-start time of LM5145? I would like to design with 200ms soft-start.
Thanks for your support!
-Ben
Hello Ben,
WeBench will fail to provide a solution if one of the parameters installed is violated. for higher current designs this is typically a temperature issue not current limit. In direct response to your answer, yes you can use Rsense as detailed in the datasheet. trying to get WeBench to provide you with a solution, try reducing the Tamb for your design. If this does not work, you could try reducing the max input voltage a little.
Alternatively you can download the calculator spreadsheet that is posted below.
Regarding the SS, please increase the soft start cap to provide the required SS time.
Hope this helps?
David.
