20x4 LCD Specs Needed to Choose Series Resistor

[d7x]

I was following the tutorial on http://www.ladyada.net/learn/lcd/charlcd.html which explains
"To calculate the value of the series resistor, look up the maximum backlight current and the typical backlight voltage drop from the data sheet." I looked at the links to the data sheet on the product page http://www.adafruit.com/datasheets/TC2004A-01.pdf but didn't see a term called voltage drop. I'm also looking for the max backlight current but only saw a term called max input or max supply voltage. What's the best way to find this info in order to pick the correct resistor?

[adafruit_support_bill]

The voltage and current ratings are at the very bottom of page 5 on the data sheet (4.2v/180mA). But that data sheet is for a yellow/green backlight.

With the white backlit units we have in the store, you can connect directly to 5v as in the tutorial photos.

[MakerDane]

I have a very similar question / problem. I purchased the White on Blue Standard LCD 16 x 2 + extras (PID 181) which has a similar backlight specification chart (Operating Voltage 4.1v, Forward Current 100mA). I'm new to this and thought the kit would include everything I would need to hook up the LCD for my project but there are no resistors included.

Is the 4.1v "operating voltage" also known as the "voltage drop"? If so, am I correct in using a (5-4.1)/0.1 = 9 ohm (or larger) resistor?

[adafruit]

if you bought it from the adafruit shop, simply follow our tutorial, the resistor is on the PCB