# CFAH1602BTMCJP whats its Iled values

#### osoi

##### New member
I can't find where you get the Iled values for the model CFAH1602BTMC JP. can someone tell me?

The SLI-OEM has a nearly-nifty feature on it that will allow control of the backlight using its "/OUT" pin. "Nearly nifty" because you can control the backlight, but you have to do some hacking around to add the necessary current-limiting resistor. Wirz should have just put two holes in their board where you could add your own current-limiting resistor. Oh well, it gets covered up in the end so we will just scab a resistor into place.

Now the math end of things. We need to calculate the size of the resistor.

R=(5v - Vled) / Iled

You need to look up the current and voltage of the backlight from your LCD's data sheet. The CFAH2002A-RMC-JP's data sheet gives these values:

Iled (normal) = 0.28 amps (280mA)
Iled (maximum) = 0.56 amps (560mA)

Vled (normal) = 0.42 volts
Vled (maximum) = 0.46 volts

So:

Rmax = (5 - 4.2)/0.28 = 2.8 ohms (normal)
Rmin = (5 - 4.6)/0.56 = 0.7 ohms (maximum brightness)
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