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Hi Nick,

We have an onboard current limiting resistor (R7) which is tied in the pin 15(LED+).

Typically, in our spec we mention the recommended supply voltage and current values not the absolute min and max values. You can provide an another 100mA to the backlight, but it depends on the user to provide a lower or higher voltage than the recommended spec values.

We provided the 3.3V for the backlight at 280mA, and noticed a drop in voltage to 3.18V.

This display has a full array backlight, which leads to the high current draw as compared to other LCDs.

Thank you.

Thanks!  This one was baffling me.

The datasheet linked from Digikey's product page (NHD-0420AZ-FL-YBW-33V3.pdf) has a table of Electrical Characteristics on pg. 5, with Min, Typ, Max columns.  Backlight Supply Voltage (Vled) is min 2.8, typ 3.0, max 3.2 V.  Backlight Supply Current (Iled) is min 200, typ 280, max 350, condition Vled=3.0V.

I couldn't figure out how the current would vary, at a fixed voltage, by about +/- 40% unless that was supposed to be read as "you should supply 280mA, +/- 40%, with an expected forward voltage drop of 3.0V, +/- 200mV" -- but then, I would've expected to see Vfwd, not Vled...  since Vled implies a source voltage -- but then why is it such an oddball voltage with such small margins?  So it really didn't make sense to me.  lol

If it's a fixed current-limiting resistor, then I can calculate an appropriate R on my side of the board to work at 3.3V and stay within the current rating.  Though 200mA really seems like a lot -- that's getting into flashlight territory.  This thing's going to light up the room.  haha  OK, I'll play with those values and see what happens.