Advantech IDK-1110P-50XGB1 User Manual page 16

Note (2) At 190 ~1kHz PWM control frequency, duty ratio range is restricted from
5% to 100%.
1K ~20kHz PWM control frequency, duty ratio range is restricted from
20% to 100%.
If PWM control frequency is applied in the range from 1KHz to 20KHZ,
The "non-linear" phenomenon on the Backlight Unit may be found. So
It's a suggestion that PWM control frequency should be less than 1KHz.
Note (3) The LED lifetime is estimated data and defined as the time when it con-
tinues to operate under the conditions at Ta = 25 ± 2 º C (77 ± 3.6 °F) -
and Duty 100% until the brightness becomes ≤ 50% of its original value.
Operating LED at high temperature condition will reduce life time and
lead to color shift.
IDK-1110P-50XGB1 User Manual 10