Re: 300 mA from a microcontroller pin

On 30 Nov 2007 13:16:33 -0500, the renowned DJ Delorie
<dj@xxxxxxxxxxx> wrote:


CBFalconer <cbfalconer@xxxxxxxxx> writes:
Ignoring total dissipation, a single tri-state driver will do:

+5
|
R1
|
tri state here >---|X|-----+
LED |
R2
|
GND

with R1 approximately equal to R2. The ratio controls brightness.

If you replace R1/R2 with the 1/2 Vcc op-amp circuit I posted earlier,
you can use a single resistor in series with the LED and reduce the
"off" leakage current.

Neither circuit will work particularly well if the Vf of the LEDs is
close to (or greater than) Vdd/2 at the desired operating point.

;-)


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
.

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  • Re: 300 mA from a microcontroller pin
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