I have a LCD Display with white LED backlight. I want to connect it to a MOSFET which will be controlled by my ESP-12E Microcontroller.
I'm wondering which resistor to use. The data sheet says:
Absolute Maximum Ratings: Back Light Forward Current ILED -- 25 mA For each LED
Electrical Characteristics: Forward Current IF -- 20 -- mA Forward Voltage VF -- 3.2 -- V
(4 LEDs parallel)
Is the value per LED?
My power supply will either be 5V or 12V
The other data sheet page says:
LED Backlight Power Supply: max. 3.2V (by 3.3V Power Supply 2-5 Ohm Resistance, or by 5V 20-25 Ohm Resistance)
But if I calculate for 5V power supply I get:
25 Ohms * 0.02 Amps = 0.5 V
Question 2: So does that mean a voltage drop of the resistor of only 0.5 which would result in a voltage of 4.5 V for the LED which seems to be too much?
Or do I have to calculate with 0.08 Amps because of the 4 LEDs?
25 Ohms * 0.08 Amps = 2 V
Would this mean the overall voltage drop is 2 V but every LED still gets 4.5 V?
For 12 V that would mean a 150 Ohms resistor?
I'm not that good at physics, I just want to make sure everything is correct so I don't damage anything.