Description of reference design

UM0677

8/16

Doc ID 15396 Rev 2

2.2

Dimming interface

For more advanced applications, the reference design also includes an interface for

dimming. The board itself does not include any signal generator, but to keep universality

with different control schemes (analog or digital dimming) a three-pin connector was built in

generator (implemented by either the microcontroller or by comparators). The PWM pin is

an universal dimming input, working with both analog and digital dimming. Any voltage

above 2.5 V is considered as 0% power, i.e. the analog dimming works in the range from

0 V to 2.5 V, where 0 V (grounding the pin) results in full power. The standard 3.3 V logic

levels can be used as a PWM control signal for digital dimming. In this case the brightness

changes from 0% (full power) to 99% (minimum power) duty cycle. If the driver is used

without the PWM generator, pins 1 (GND) and 2 (PWM) on the PWM connector must be

connected together.