TFT LCDs — DRIVER ICs and INTERFACES

By Jack Powers, Application Engineering Manager at New Vision Display, Inc.

TFT LCDs are becoming the norm for small-to-medium size displays in a variety of products within industrial, medical, POS and consumer applications. Compared to passive-addressed monochrome LCDs, TFT Displays offer higher contrast, wider viewing angles, faster response time and full color. And, TFT LCDs are now on cost parity with similar size passive LCD displays.

A typical TFT LCD module product consists of a TFT LCD panel, one or more COG (chip-on-glass) driver ICs, a backlight unit and an interface FPC. Several TFT display interface technologies coexist today. Picking the right technology depends on the specific end-product concerns. Most often the display panel input will dictate that choice since TFT panels are designed to be COG bonding pad compatible with a very limited number of driver ICs. This article discusses the interfaces between TFT LCD modules and the typical CPUs found in embedded applications.

Typical TFT interfaces are determined by the particular TFT panel size and resolution:

• Up to 3.5” size with 128×160 to 240×320 resolution – normally have SPI, parallel MPU or RGB interface
• Between 4.3” and 7” sizes with 480×272 to 800×480 resolution – mostly have RGB interface
• For mobile displays with resolution higher than 480×854 – normal interface is RGB, MIPI or LVDS
• For 7” size and above with 1024×600 and higher resolution – normally have LVDS or MIPI interface
• HDMI and eDP require interface converting boards and generally are not use for small-to-medium size TFT LCDs

As a designer and manufacturer of custom LCD modules, New Vision Display works with customers to select the most appropriate and cost-effective TFT display and electronic interface solution for their particular requirement. New Vision Display has nearly 30 years of industry experience as one of the world’s leading TFT LCD screen manufacturers. For more information, please visit www.newvisiondisplay.com

Article Source: https://goo.gl/zx2ln2

The technology behind sunlight readable LCD Display

For many years now, TFT LC-Displays have been the dominating technology in visualization. With more and more screens being used outdoors and in portable applications, sunlight readability has become a critical factor in the display market. One way many LCD manufacturers address this issue is to increase the display’s backlight luminance. Although this works well for many applications, it also increases power consumption and the bulkiness of the display. This is not an ideal solution for some portable or small-size applications, so NVD additionally offers “transflective” displays, which have improved readability in any lighting condition without increasing power consumption or bulkiness.

Simple, low resolution liquid crystal displays routinely are offered in reflective, transmissive, and “transflective” (partially transmissive and partially reflective) mode. This is achieved simply by choice of the reflector behind the display , which is usually attached to the rear polarizer. This method is not feasible for TFT displays due to the inherently much lower transmission of these devices. Transflective TFT displays have a unique cell architecture compared to standard TFT display modules. This is necessary to accommodate for the fact that light passes only once through the liquid crystal layer in transmissive mode before reaching an analyser, while in reflective mode it passes the liquid crystal layer twice. In the transflective cell architecture, every single pixel is divided into a transmissive and a reflective section, where the latter is based on a polymer film with micro metal mirrors within the glass cell. The size and partition of these two sections are flexible and depend on the desired focus of the final display. Typically the liquid crystal layer thickness in the reflective part is only half of the call gap in the transmissive part. The front polarizer acts as both, polarizer and analyser for the reflective portion of each pixel. This requires selection of a liquid crystal mode that works with parallel polarizers, unlike transmissive displays where usually polarizer and analyser are crossed.

                                   Image 1 — Transflective Display Cell Architecture

Written By Frank Jammers (FAE for Europe) and Matthias Pfeiffer (CTO) at New Vision Display

Article Source: http://goo.gl/HBdWM7