Data Sheet

WLMDU9456001JT / 172946001
MagI
3
C Power Module
LDHM - LED Step Down High Current Module
We-online.com rth Elektronik eiSos GmbH & Co. KG – Data Sheet Rev. 1.0
© May 2016 21/35
PWM Dimming
Controlling the brightness of the LED emitted light while keeping the same color can be achieved by properly driving the
LED. A well-known limitation of the human eye is not to distinguish light flickering with frequency above 100-120Hz. The idea
of the PWM dimming of LEDs means simply switching on and off the LED above this frequency. The human eye will
perceive the color corresponding to the current flowing through the LED during the switch-on phase. It will implement a kind
of integration of the perceived brightness, corresponding to the average current flowing through the LED, as described in the
picture below:
I
LED
t
Average current BRIGHTNESS
I
LED,peak
COLOR
The 172946001 offers the possibility to implement a PWM dimming by using the dedicated pin DIM.
The DIM pin of the LED driver module is an input with internal pull-up that accepts logic signals for average LED current
control. Applying a logic high (above 1.3 V) signal to the DIM pin or leaving the DIM pin open will enable the device. Applying
a logic low signal (below 0.7 V) to the DIM pin will disable the switching activity of the device but maintain the operation of
the internal voltage regulator (VCC).
0
100
200
300
400
500
0 4 8 12 16
LED current [mA]
time [ms]
PWM dimming
0
2
4
6
8
10
0 4 8 12 16
PWM dimming signal [V]
time [ms]
Example with PWM dimming frequency of
250
Hz