At 11:49 AM 5/16/2006 -0700, you wrote:
>We currently have several products running off an unregulated external
>12VDC power supply (wall wart). Inside our product, we run through a
>1N4001 for reverse polarity protection, then 1n LM7805 to regulate to +5V
>(to run the PIC!). Upcoming California Energy Commission regulations
>outlaw these external power supplies (due to lack of efficiency and
>standby power). We could replace these with 12V regulated switchers, but
>that is pretty inefficient. What I'd like to do is replace them with
>external 5V switchers, yet continue to allow the use of the old power
>supplies. It would be great if there were an LDO equivalent of the TO-200
>LM7805 with reverse polarity protection (so I could get rid of the diode
>and its drop). Anyone aware of a drop-in replacement?
>
>THANKS!
>
>Harold

LM2940C mostly meets your stated requirements. Of course you'll need a bit
more than 5V in to get 5V regulated out! If you're just using the regulator
as a low-drop diode, it's a bit expensive, but might be acceptable if it
means you don't have to do another PCB for a low-volume product.

Note also that they are not kidding on the minimum output capacitance
required for stability (22uF in this case), so it may not be 'drop in'
in your particular case. The ESR must also not be too high or too low,
or again it may oscillate (don't use a ceramic 22uF cap, for example).

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->>Test equipment, parts OLED displys http://search.ebay.com/_W0QQsassZspeff


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