Needed: 12-24V to 5V regulator @ 60-100mA

Linear for car perhaps, but not bus. Even a less efficient switcher is better than linear. My guess is more than 50% for 24V @ 100mA.

It depends on the designer/manufacturer.

Looks nice, dirt cheap. MC33063 is probably better for my needs, as it is supposed to operate from -40 celsius. Gonna give it a try probably, thanx !

BR, Przemyslaw

At those current levels, a switcher using an MC34063 is suitable. I use them a lot at that sort of current level. In fact, most of the el cheapo mobile phone in-car chargers use it. DIP-8 chip, one diode, four resistors, a cap and an inductor. Pretty simple, schematic in the data sheet.

car's aren't nice 12V supplies, your finished device should be able to withstand various fault conditions

eg: a load dump where the battery goes flat and then opem-circuit, and everything takes a hit from an altenator with the field current wound all the way up, upwards of 80V can be developed, this'll destroy lm317 and

auto electrics are often horribly inneficient 20% is no big deal,

that bus will be closer to 27V typical by the way.

the commercial units I've seen used switchers of some type

if you only need one it's easiest to just buy a "cigar-lighter to usb" adaptor.