I have a project where my power supplies are giving me a bit of a headache. I have three voltage regulators that I am trying to run from a single bench power supply. There are two 3.3V regulators, and one 12V regulator. The current draw for the 12V regulator is up to 500 mA, and each 3.3V regulator peaks at 150 mA.
When I hook up about 14V to the inputs of these regulators, the 3.3V regulators start to cook. Doing the math, that's about 1.7W of power dissipation for each of the 3.3V regulators. They're in a TO-220 package pointing straight up, and they got too hot to touch. I was able to throw a random heatsink I found on the tab and cool things down, but the top of the heatsink was about 2.5 inches high - very flimsy and cumbersome.
I really don't want to sacrifice the single power supply input, and I also really don't want to go to an on-board switching supply for either the 12V or 3.3V supplies. What are some passive package+? solutions for dissipating up to 2.0W of heat that are physically secure and low profile (shorter than 1 inch)?
Edit: My reasons for not wanting a switching supply are:
- I don't want to deal with switching noise in the analog parts of my design
- I'm less comfortable with designing a switching regulator than using a linear regulator
- The PCB that I'm working on is big and expensive. I don't have the time/budget to "try out" a regulator. A linear regulator with enhanced heat dissipation seems a lot safer way to avoid making coasters than a switch mode regulator.