Noob Q - LM337 SOIC: four Vin's?

Heat sinking. You usually need a fairly big copper pour.

Cheers

Phil Hobbs

What Phil said -- the input of that chip is connected to the collector of the output transistor, which is where most of the heat is generated. In that package, the way you get heat out is through lots of pins.

This is a big driver for different linear regulators having different pinouts -- because depending on the regulator layout, the heat- dissipating portion of the circuit will be connected to different pins, and the manufacturer wants to provide you a way to get that heat out.