Re: Anotehr Basic Q. re: a circuit

"Phil Allison" <philallison@xxxxxxxxxx> wrote in
news:6fnau0FcgjgqU1@xxxxxxxxxxxxxxxxxx:


"Kris Krieger"

Sorry for another stupid question, but, I'm looking at this
http://www.maxim-ic.com/appnotes.cfm/an_pk/1750
and can't figure out whether I can ignore, or whether I need to add
in some
modification of something like this
http://www.instructables.com/id/S8Q5N9QFHTAIQK7/
where the first diagram says
" PWM Dimming 0 to 3.3HZ f>15KHz 0%=shdn 100%=20mA "

A clue would be appreciated - especially since I don't know whetehr
they mean dimming as in a Dimmer Switch on a lamp, or whether they
mean something entirely different...


** The CTRL input operates to dim the LEDs with a 0 to 3.3 volts
variable DC input, which can be created by filtering a PWM signal as
shown or any other way you like - eg with a 3.3 volt supply and a
pot.




..... Phil


In the Data*** for the IC, in the chart describing the Pins, for CTRL, it
says:
"Brightness/Shutdown dualmode control input. LED brightness and IC
shutdown are controlled by the voltage on CTRL. VOltage between 250mV and
5.5V or (V+ + 2V), whichever is less, adjust the brightness from dim to
bright, respectively. To put the IC into shutdown, drive below 100mV or
connect to GRND."

So, for a low-voltage light (2 or three 1.2V NiMH batteries, 1500mA to
2500mA), that means it's jsut personal choice rather than mandatory to add
in the dimmer?, IOW, I can either add in a dimmer, or just connect the pin
to the ground/out terminal?

Sorry, I'm very much a beginner still, and the Appliocation Notes aren't
clear to me re: whether teh dimming is optional or required...

Thanks!

- Kris
.