Description:
This 20-character, 4-line parallel liquid crystal display provides a large viewing area. It features white text on a blue background OR black text on yellow green background with an LED backlight and uses the common HD44780 parallel interface.
Pin out:
| Pin | Symbol | Function |
| 1 | Vss | ground (0 V) |
| 2 | Vdd | 5 V logic supply voltage |
| 3 | Vo | contrast adjustment |
| 4 | RS | H/L register select signal |
| 5 | R/W | H/L read/write signal |
| 6 | E | H/L enable signal |
| 7~14 | DB0 – DB7 | H/L data bus for 4- or 8-bit mode |
| 15 | A (LED+) | backlight anode |
| 16 | K (LED-) | backlight cathode |
This LCD has an LED backlight. The voltage drop across the LEDs is typically about 3.2 V and the recommended current through the LEDs is 72 mA. This LCD includes a 25.5 Ω resistance (two 51 Ω resistors in parallel) in series with the backlight, so an external current-limiting resistor is not required for backlight supply voltages up to 5 V. For higher voltages, you should add a current-limiting resistor RLIMIT as shown above where:
RLIMIT = (VBACKLIGHT – 3.2V) / 0.072A – 25.5Ω
Any voltage above the diode-drop voltage will work (as long as you choose the appropriate value for your external current-limiting resistor for voltages over 5 V). You can also use a PWM-controlled MOSFET to achieve variable dimming of the backlight if so desired.
