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What Determines How Many Pins My LCD Will Need? Explained

Graphic display LCD pins explained image

When you sit down to enjoy your favorite handheld gaming console, use a digital multimeter for work, or rely on a GPS to get somewhere remote, have you ever wondered what’s behind the display? These LCD (liquid-crystal display) screens are compact, clear, and handy, made up of a variety of different components that come together to produce the vivid pictures we see. And getting the exact number of pins right is the key to its smooth operation.

But why focus on such a seemingly small component such as pins? While they might not be as interesting as the touch technology or pixels on the screen, the pins are what make up the foundation of the screen. Without them, your screen wouldn’t know how and when to light up to produce the right images.

What Are Pins in an LCD?

When we talk about pins in the context of an LCD, we refer to the physical nodes within the device that help connect multiple communication points between the different component circuits. If you take a device apart, you can see these protruding from several chips on parts of the electronic product. To better understand, you can imagine them transporting data and power from one part of the device to another.

The purpose of all these pins is to create a web of connections that make sure the LCD functions properly. Different pins are responsible for different functions, just like each employee in a company works to fulfill a certain role. For example, some pins might be used for power supply, while others are used for data communication. We’ll get into these different roles in a later section.

What Determines Pin Number in an LCD?

If you look at the inside of an LCD, you might wonder why some screens have more pins than others. This isn’t just to do with the sheer size of the screen. It takes into consideration several other essential factors as well, including:

Type of the Display

Whether it’s a TFT (thin-film-transistor) LCD display or a  Character LCD, different types of displays require varying numbers of pins. For example, a TFT display typically requires more pins because of its high resolution and color depth in comparison to simpler character displays.

Size and Complexity of the Display

Of course, screen size and its intricacy will determine how many pins are needed. Larger screens with more complex circuitry usually require more pins than smaller LCDs with simpler circuitry.

Functionality of the Display

A display that’s only used for showing numbers or a few lines of text will naturally need fewer pins than one that’s used to display complex images or videos. These more complex screens require more pins to handle the larger demand for power distribution and data transmission.

Additional Features

When it comes to displays with extra features like backlighting and touchscreen, this could affect the number of pins required. These added pins are used to process touch or control and manage the lighting component, for instance.

Interface Type

The most significant factor in determining the number of pins is the interface type that is used.  If the LCD has an included driver on the panel (as most do), the driver will provide the user with an interface such as I2C, SPI, Parallel or MIPI DSI.  While each of these has different benefits, the primary benefits of I2C and SPI are the low pin count.  Parallel interfaces tend to require higher pin counts due to their method of data transmission.  The MIPI DSI interface is a lower pin count alternative to Parallel interfaces for TFTs that do not work well with SPI or I2C interfaces.

Understanding Specific Pins in LCD Displays

LCD pins can usually be divided into three main categories: power pins, control pins, and data pins.

Power Pins

Power pins are all about supplying power for the LCD to operate on. These pins provide the voltage level required to activate the liquid crystals within the display. When they do so, they’re able to run the LCD and control how bright the screen gets.

Control Pins

Control pins are in charge of operations. This includes instructing the screen’s internal workings to perform certain tasks such as adjusting screen settings, controlling display patterns, and managing data flow. All messages associated with the LCD go through these pins.

Data Pins

 Data pins carry the data displayed on the screen, sending the required information between the LCD’s actual visuals and its control system. For example, when you’re playing a game, the animations you see are all ‘created’ through these data pins.

Importance of Understanding Pin Count in Functionality of Small LCDs

Pin numbers are meticulously calculated based on the needs and complexity of the display.  The pin count impacts the other critical components in the display. For this reason, it is paramount to consider pin count early in the design process.  For example, if you select a high pin count LCD module, it will in turn require an MCU capable of driving so many pins.  In most cases this can have a large impact on the MCU costs. It can limit MCU choices which may not be desirable in today’s world of frequent supply chain shortages on MCU chips.

Larger numbers of pins can also create a more complex PCBA design and complicate the firmware development.

Conclusion

Understanding the role and number of pins required in an LCD isn’t just technical knowledge for electronics enthusiasts or experts. It can actually be the key to choosing the most effective LCD for your devices or projects. As pin determination is such a calculated decision based on the requirements of an LCD as well as the other aspects of the design, knowing the ins and outs of LCD pins can help you guide you in making more informed decisions.  Focus LCDs’ team members are experts in LCD design and will take into consideration all aspects of the project including your MCU and help make decisions as to what LCD modules and pin counts are best for your application.