An Introduction to TFT (Thin Film Transistor) Displays
TFT(Thin Film Transistors) Displays are the most popular type of color display. They can be seen in such products as TV’s, tablets, digital photo frames and countless other devices.
BENEFITS AND USE
TFT’s are a full color modules that can display graphics, characters and video and are great for adding an interesting user interface to any product.
- Can display up to 64 million colors
- Operates down to -30C
- Available sizes from 1.4” to 15”
- Larger and smaller TFT sizes are available with several off the shelf options available
- Active and passive matrix options
- Active matrix technology is used on larger displays that require a faster refresh rate and provide a sharper image.
- Passive matrix technology is used on smaller displays where each pixel can be refreshed in a cycle.
- Wide viewing angles
- TFT’s are readable from a wider range of rotation than many other LCD technologies.
- Multiple interface options (RGB, LVDS, Parallel, SPI, HDMI)
- RGB is very affordable and offers fast communication but requires many pins from the microprocessor to drive the data bit lines .
- SPI (Serial Peripheral Interface) requires few pins from the microcontroller but communication is slower than other interfaces.
- LVDS (Low Voltage Differential Signal) provides an ultrafast communication and refresh rate necessary for larger displays. LVDS is more expensive than other types of bus, such as RGB and parallel.
Things to consider with TFTs:
- Transmissive TFTs, which are the most common, can be power hungry. If power is a concern, it may be worth considering an IPS TFT or a Transflective TFT.
- Transmissive TFT modules can only be read when the LEDs are on. This can quickly drain a battery, unlike a monochrome graphics display that can be read with or without the backlight on. IPS TFTs have the same issue, but can function with less power consumption than the common amorphous silicon TFTs. Transflective TFTs allow the panel to work without the backlight at all.
- Many TFTs are available at similar prices to like-sized monochrome displays now, however, the driving power required for a TFT may inflate the cost of the microcontroller and also require more extensive programming efforts to get the display up and running.
- Sunlight readability
- The greatest majority of TFTs integrate a Transmissive polarizer. Transmissive TFTs are only readable with the backlight on and for sunlight readable applications, it is important to use a Transmissive TFT with a high brightness.
- Transflective TFTs are also available in some sizes. These are readable using ambient light as well as the backlight and can be a good option for sunlight readability.
Value added available:
- Touch panels
- Resistive touch panels are the least expensive option and come standard for most TFT sizes. They are great for rugged applications and read touches by pressure which allows them to be used with gloves or any other object.
- Capacitive touch panels also come standard for most TFT sizes. They allow for multiple touch points, gestures and can read precise touch points. Capacitive touch panels can also act as a cover glass for the product and can be developed to include ambient light sensors, printed company logos and other items.
- Brightness (nits) can be increased
- Customizable FPC cables, LED backlights, bezels and touch panels
- Selectable interfaces