> It occurred to me that there must be an enormous range of constant-curren=
t
> switch-mode LED drivers available.  But my couple of hours searching has =
not
> found anything that I can purchase easily from Western Canada.  In other
> words, I'd like to find something that I can purchase from Digikey or Mou=
ser
> or Newark or Future.
>=20
> My best guess is that I'm not using the right search terms.
>=20
> My requirements are:
>=20
> 28Vdc max input voltage
> 10mA output current
> works down to -45C or colder
> readily available from North American distributors
>=20
> Does anyone have any suggestions?

I don't think these really meet your requirements, as they are boost regula=
tors for a string of LEDs, but may lead to other chips and app notes that m=
ight solve your problem.

The Microchip graphics display development cards have a PWM controllable bo=
ost regulator to drive the back lighting.

4.3" display (data sheet DS51844A) uses a Micrel MIC2289-34YML from 5V.
3.2" display (data sheet DS51789A) uses a Linear Technology LT1937ES5 also =
from 5V.

In both cases they measure the LED current with a sense resistor in the gro=
und side as the feedback into the regulator.


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