DESIGNER’S HANDBOOK 4189350049C EN Page 76 of 206
and like previously described for the HV input, it is possible to overwrite the reference voltage by an external
voltage (7.5-30 V) and still get fluctuations corrected.
It is recommended to use a potentiometer in the range from 1 to 20 kΩ.
5.6.9.15 Dimmer input using PWM
The XDi does not directly support PWM (Pulse Width Modulation) input for dimmer control, but it is possible to
route the PWM signal through a low pass filter to obtain a DC voltage at the analogue input. The high input
impedance (112 kΩ) of the analogue dimmer input limits the load of the RC filter.
The PWM frequency should be as high as possible to be able to filter hard to avoid backlight flicker and keep a fast
response.
The resistor R should not exceed 5 kΩ, and the capacitor C can be calculated as:
𝐶 =
10
2𝜋 𝐹 𝑅
[µF]
Where F is the PMW frequency in kHz, resistor in kΩ and the capacitor C in µF, the max/min dimmer input voltage
span should be adjusted via the menu to best match the usable voltage range from the PWM signal.
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