Texas Instruments provides a recommended PCB layout in the LM3445 datasheet, which includes a thermal pad connected to a copper plane on the PCB to dissipate heat. Additionally, it's recommended to use a 2-ounce copper PCB and to keep the thermal pad away from other components to minimize thermal resistance.
To ensure reliable start-up, it's recommended to add a soft-start circuit to limit the inrush current during power-up. This can be achieved by adding a resistor and capacitor in series between the VIN pin and the input voltage source. Additionally, the input voltage should be ramped up slowly to prevent high inrush currents.
The maximum output current capability of the LM3445 is 4A, but it's limited by the thermal performance of the package and the PCB. The actual output current capability will depend on the ambient temperature, PCB layout, and thermal management. It's recommended to derate the output current based on the junction temperature and thermal resistance of the package.
To protect the LM3445 from input voltage transients and surges, it's recommended to add a TVS (Transient Voltage Suppressor) diode or a voltage clamp circuit between the input voltage source and the VIN pin. This will help to limit the voltage spikes and prevent damage to the device.
The recommended input capacitor value is 10uF to 22uF, with an X7R or X5R dielectric type. The input capacitor should be placed as close as possible to the VIN pin and should have a low ESR (Equivalent Series Resistance) to minimize voltage ripple and noise.
LM3445MMX/NOPB datasheet
by Texas Instruments
