20x4 Character LCD with LED Backlight (Parallel Interface), White on Blue

This white-on-blue 20 x 4 LCD can be used to add an eye-catching display to your electronics project. An LED backlight enables viewing in dim lighting conditions. This unit uses the HD44780 interface found on most parallel character displays.


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Our Code: SKU-002544

Supplier Link: [Pololu MPN:1219]


Dimensions (in mm) and pinout for the 20x4 white-on-blue character LCD with backlight


This 20-character, 4-line parallel liquid crystal display provides a large viewing area. It features white text on a blue background with an LED backlight and uses the common HD44780 interface, so sample interface code is widely available for a variety of microcontrollers. This display is electrically compatible with the LCD that is included as part of some of our Orangutan X2 robot controller packages, although the physical interface is different.

You can find sample HD44780 LCD interface code written for a variety of AVR microcontrollers as part of the Pololu AVR library.

20x4 white-on-blue LCD displaying the Pololu logo with custom characters


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

Using Contrast and the Backlight

As shown in the diagram above, a potentiometer whose output is connected to Vo will allow you to set the contrast for optimal viewing of your display.

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.

Note: No cables or connectors are included with this product, but a straight or right angle male header can be purchased separately to be soldered into the through-holes. We also have 1×16-pin female headers and crimp connector housings to mate with the male headers. This LCD is intended for use with 5V systems.



Size: 98 x 60 x 14 mm
Viewing area: 76 x 26 mm
Dot size: 0.55 x 0.55 mm
Character size: 2.95 x 4.75 mm
Weight: 78 g

General specifications

Minimum logic voltage: 4.8 V1
Maximum logic voltage: 5.2 V1
Typical LED backlight voltage drop: 3.2 V2
Typical LED backlight current: 72 mA
Supply current: 1.2 mA


This LCD is not intended for use with 3.3V-logic systems (the input high threshold, VIH, is 4 V).
Voltage drop across the LEDs only. This LCD has a built-in 25.5 Ω current-limiting resistance in series with the backlight LEDs.


File downloads

HD44780 interface datasheet (330k pdf)
This document details the HD44780 parallel interface that is an industry standard for dot-matrix LCDs.

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