LED Driver PWM control

Other Hardware General Electronics
1

Hi,

I am looking at this led driver http://media.digikey.com/pdf/Data%20Sheets/ON%20Semiconductor%20PDFs/CAT3604.pdf

If i want to use PWM to control the brightness of the LEDs, do i just need to use analogWrite to achieve this?

Thanks

2

Yes, to the control inputs. But note there isn't a direct mapping from one control
input to one LED - there are 3 control inputs selecting 8 possible patterns (table 6).

3

Thanks,

If i instead used this led driver Technical Documentation, changing the PWM based on analogWrite will control the LED brightness?

Also, i'm assuming the current is less when the LEDs are not as bright, and most when full brightness?

Cheers

4

Also, i'm assuming the current is less when the LEDs are not as bright, and most when full brightness?

Not exactly... PWM switches the LED on & off faster than you can see it flashing/blinking. The current is the same for the period of time the LED is on, and the current is zero when off.

So, the average current is less but the peak current is the same. And in fact, the LED isn't "dim", but your eye perceives it as dim. (If you apply PWM to an incandescent lamp, it will be truly dim because it takes a fraction of a second for the filament to heat-up an start glowing.)

P.S.
I believe some constant-current power supplies for high-power LEDs actually do lower the DC current while dimming, even if they are "PWM controlled".

5

That device has a single PWM compatible EN input controlling all four channels,
so yes it will be usable.