You will find  power supply chips for Telecom circuits does this. First try
siliconix, then maixm, linear tech, SGS, to name few. U/Interface on ISDN
is powered from 48V to 5V converters.

Regards,

Jay

PS If I find part numbers I will post it next week.

At 14:28 14/05/99 -0400, you wrote:
>Anybody know of a SMT regulator which can handle 45V input, 5V/50mA output?
> 40V * 50mA = 2W - an awful lot for a tiny PCB to handle.
>
>I'm finding very few options in the datasheets.
>
>PCB size is a premium. Reliability is SUPER important, component
>cost/complexity is secondary.
>
>Ideas?
>
>Thanks!
>
>Andy
>
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