LM25145: schematic review

Hi Fred,

The quickstart file looks okay. Check the MOSFET parameters again and make sure to enter the correct Rdson and Qg at Vgs = 7.5V (when using paralleled FETs, use Rdson /2 for the effective Rdson and 2x for the capacitances and charges).

The Rdson of the FETs is quite low here, so you may not need paralleled FETs.

Regards,

Tim

Also, check the effective Cout and ESR (the ESR is high). Recommendation is to use a few ceramic caps to reduce the ESR, e.g. 47uF/10V or 100uF/6.3V.

Similarly, you need ceramic input caps right at the FETs, e.g. 10uF/50V. The electrolytic does not provide low enough impedance for the high di/dt input current. You can also add a 2.2Ohm in series with the VIN pin for extra filtering to the IC.

The inductor can be 2.5uH or 3.3uH (no need for 4.7uH as the DCR is too high).

This design is quite similar to the LM5145 EVM (5V/20A/225kHz), so you can review the component choice there as well.