Original Post by Bob Waddell, Dec. 7, 2008

In recent years, the 7.0″ wide VGA (800 x 480) digital TFT has become one of the most popular displays in the world. The consumer applications are numerous – portable DVD, rear seat entertainment and especially digital photo frames use this display in the tens of millions annually. There is a great deal of interest in this product for commercial and industrial users too, and for good reason:

• A 7.0″ wide TFT has an active area of approximately 6″ x 3.6″, which is easily visible
• The wide format display makes it a perfect choice for applications where two windows are desired – say, one window for a graphic image, the other for related data
• It is large enough to have a touch screen that can be easily used

However, the immense volume of the 7.0″ WVGA in the  marketplace has created an issue in the industrial space. The TFT manufacturers who focus on the industrial market are committed to supplying displays that provide the following key features:

• Long term support — minimum 3 to 5 years
• Wide operating temps — -20 to +70C is standard
• Backward compatible design changes — if a product is modified, it is relatively transparent to the user: Mounting hole locations and connectors don’t change; interfaces and pinouts don’t change; and the supply is not interrupted.

The high volume of 7.0″ consumer displays has driven prices down so low that many of the industrial suppliers initially did not offer a product. Consumer suppliers, when seeing a periodic slowdown in demand, would flood the market with their products at prices far below what the industrial TFTs can build them for. It is not unusual to see a consumer-grade 7.0″ WVGA TFT available at a fraction of the cost of an industrial display.

There are now several industrial TFT suppliers that offer a 7.0″ WVGA TFT in a variety of configurations:

• LED or CCFL backlight
• Up to a -30 to +80C operating temp
• With or without touch
• TTL or LVDS interface

None of these are available at pricing comparable to the consumer products that come into, then exit, the industrial space. But that is not the market that they are competing against either.

Every OEM company needs to do what is in their best interest when it comes to deciding what display is the best choice for their product. It is extremely important to keep in mind that long-term availability, a consistent product offering and uninterrupted supply can save a tremendous amount of time and engineering resources just a few years down the road.

Original Post by Vignesh Sanmugam, Dec. 5, 2008

The trend of the twenty-first century is that everything is going flat: the world, the economy, the stock market and, now, even displays —flat panel displays (FPDs) are everywhere.  LCD TVs and LCD Monitors have dominated the consumer market with their aggressive pricing and extensive marketing.  And let’s not forget about consumer favorites such as iPods and other MP3 players, mobile phones, PDAs and kids toys. As the prices for TFTs plummet, displays will continue finding their way into almost every possible application (including the toys for your children’s Happy Meals). The technological advancements within the Flat Panel Displays are making designers’ dreams a reality. The choice of designing with a display has thus become inevitable, but the dilemma is “Which display do I use?”It is always that first step which is a challenge, but with displays it is one the easiest decisions. From the CEO to Marketing, everyone wants a Flat Panel Display in their product, which is no longer a luxury but a necessity to be competitive. It is assumed for this discussion that the overwhelming consensus is to move forward with a TFT Display over Color Passive LCD or Organic Light Emitting displays. As one steers through the requirements for a TFT Display, a broader outline consists of mechanical specifications, electrical specifications, optical specifications, environmental specifications and functional specifications.

Deciding the diagonal of the display establishes the foundation for the design process. This is based on the application and the overall mechanical considerations of the final product. Flat Panel Displays are generally categorized as Mobile/PDA Displays (1.0” to 3.5”), Small Displays (3.8” – 7.0”), Medium Size Displays (8.4” to 12.1”), Monitor Displays (15.0” to 19.0”), Large Displays (20.1” to 32”) and Signage Displays (32”+).  The displays that are developed for the industrial market place are considered to have a minimum 3 to 5 years life cycle and the specifics are subject to each display manufacturer’s focus and road map. The LCDs that are developed for the mobile and laptop market tend to be volatile from a lifecycle perspective and this is where your distributor’s knowledge base is of great value in making your selection process.

The size of the display and the resolution of the screen are somewhat interrelated. As for the resolutions, there are limitations to what is available with the size of the screen. The size of the screen and the Aspect Ratio (the ratio of width to height) signifies the maximum available pixel options for the selected display. Wide format displays with mostly a 16:9 aspect ratio were initially used in AV applications and are now commonly sought after for many industrial applications too. TFT displays are either based on a-Si (amorphous silicon) or p-Si (polysilicon), with the p-Si having the ability to accommodate a higher pixel density within a given display size. In addition the p-Si technology has many additional advantages such as the driver IC integrated into the substrate, high-aperture ratio and increased electron mobility. There are now many displays with nonstandard resolutions that could be of interest depending upon the application. The viewing angle of the display is another design consideration that is based on the application and the angle of user interface. One of the challenges with the viewing cone of the display is the issue of color shifts that could significantly impact the selection of a particular display or manufacturer. Most TFT manufacturers now have displays that have wide and symmetrical viewing cones. 

The brightness and contrast of the displays are the next vital part of the selection process. The display brightness is measured in “nits”, which is a unit of illuminative brightness equal to one candela per square meter that is measured perpendicular to the rays of the source. Contrast Ratio is a measure of the brightness of white to the darkness of black that the display is capable of producing. If this ratio is high, the image tends to be sharper and vibrant. The application and the environment under which the display is to be utilized / viewed determines the target levels of the brightness and contrast required for the LCD that is being selected for the given purpose. Note that determining the optimal combination of brightness and contrast can pose a challenge as these are perceived values based on each individual. A general rule of thumb with respect to brightness and contrast is that decreased brightness can be compensated by increasing luminance contrast.

One of the design considerations in determining the brightness of the display is the backlight system of the display. Until recent time, most displays incorporated CCFL (Cold Cathode Florescent Lamp) back lights. The CCFL backlight system contributed to the major part of the power consumption of a display. In addition, these CCFL backlights required a high voltage kick-off for the start and this not only increased the need for an additional component (and inverter), but also could pose interference issues for the smooth functionality of the Flat Panel Display. The increased demand for low-power solutions, instantaneous kick-off during extreme cold weather conditions, EMI/noise issues and thermal management challenges, more and more displays are now manufactured with LED backlights. Thus, the selection of the backlight system also targets any and all power requirements of the display/application. The whiteness of the white LEDs can deteriorate over a period of time, which can impact the color performance of a display, but LED backlights hold far more benefits over CCFL backlights, especially as LED costing continues to decline.

The critical component of designing displays is to ensure that the display being selected for the application can be appropriately driven by the electronics that is available to the designer. The display interfaces differ from panel to panel and manufacturer to manufacturer. In the digital world, displays with resolutions of VGA and above fall into two main categories – CMOS/TTL, which is a parallel interface or LVDS which is a serial interface.  Whereas sub-VGA panels can vary between built-in capabilities, directly accepting TFT signals or the need for specific Timing Controllers (TCON) to provide the required signals to drive the display. Driving these displays can be accomplished in many ways depending upon the application and or available resources.

The panels can be driven (i) Directly by Microcontrollers / FPGA (ii) Single Board Computers or (iii) AD Controller Board. The current day processors, controllers and/or FPGAs have the necessary built-in capabilities to drive a TFT display. This largely depends upon the display if it is a 6 or 8 bit/color LCD. Another option is for the display to be driven by an SBC which has built-in TTL or LVDS capability. It is critical that the timings are appropriate to ensure effective functions of the Display. In an event the Single Board Computer selected does not have a TTL output for the Display but only LVDS and the display is a TTL one , you can use a low-cost conversion board. The off the shelf option is to use a standard Display Controller Board that is capable of accepting the required input such as analog RGB or S Video or Composite Video or DVI and drive the appropriate CMOS/TTL or LVDS display.

Thus, the critical design considerations for a TFT Display are: its size, resolution, brightness, contrast ratio, viewing angle, back light system, power and interface.

For any questions, please comment or email us at ask.lcd@avnet.com.

Photo of an Industrial 3.5-inch TFT Module from Sharp

New designs for industrial applications using thin film transistor active matrix LCDs (better known as TFTs for short) are booming. Pricing for TFTs continue to decline as new fabs come on line, new techniques to improve manufacturing efficiency are implemented and overall TFT supply continues to grow. Although these new fabs generally support consumer goods (televisions, monitors, MP3 players, GPS & Navigation devices, phones, etc.), they also help the industrial market by freeing up space in the lower-gen fabs which means greater capacity for industrial-grade glass. Many customers are moving away from older technologies (i.e. STN, CSTN, etc.) in favor of TFTs because of relative price parity and the inherent superiority of TFT optical characteristics. Another driving impetus for increased TFT demand is power, or lack thereof.  The evolution of low-power TFTs and low-power semiconductors now allow TFTs to be used in applications previously unthinkable. Hand held applications abound across all vertical markets and the age of the Dick Tracy video communicator wrist band is here (in fact, we’re helping many companies design very similar products).

And, of course, as costs for TFTs keep dropping, new designs for TFTs come out of the woodwork (literally…and you’ll see what I mean in a minute). Because of low cost, abundant supply, better power characteristics, improvements in overall TFT technology, etc., many customers that have never designed with TFTs are now doing so. Why? Well, at the very least, to make their products more appealing because it’s universally accepted that TFT’s are cool. And TFTs can help anyone’s product look cool too. On a more practical level, these new, non-traditional TFT customers may also be looking to provide a quantum leap in user interface or performance or usability or ruggedness. The obvious example of this phenomenon would be in instrumentation and test equipment, where it only makes sense to upgrade analog or passive displays to something faster, more accurate, more intuitive and something more cool (because marketing is an important aspect of any new design). However, my favorite example of new non-traditional customers now designing with TFTs is a medical OEM who has been one of the largest manufacturers of x-ray light boxes. Historically, this customer purchased lots of wood, opaque plastic and hardware. However, as TFT technology continues to evolve (in combination with our nation’s investment into health care, HIPPA legislation and the continuous technological overhaul of our nation’s hospitals), this non-traditional customer is looking to replace their conventional light boxes with high-resolution, multi-megapixel displays that can pull-up patient x-rays and other medical scans (along with other pertinent patient data) from the server instantaneously. This customer is a great story, but there are many more just like them.

Although the market and supplier base for TFTs is fairly mature — the industrial TFT market was established well over a decade ago — the rapid adoption of TFTs for new designs combined with the influx of new TFT sources out of Asia has stirred up the supply chain and caused some confusion among industrial customers. In many respects, it’s the Wild West and paradigms are shifting.

Most notably, the heavy adoption of TFTs within the consumer market has resulted in rapid price degradation for consumer display. As a result, many engineers like the look of these consumer displays and, more importantly, they also like the low cost of these consumer displays as well. Consequently, we receive calls everyday where an engineer has cracked open the latest commercial navigation device, DVD player or monitor in an effort to base their new design on the TFT embedded within the device.  Once these customers move down the path with their design effort, however, they find it near impossible to find engineering support or stable supply. Worse yet, consumer displays are constantly being spun to improve yields, performance, etc. which cause tremendous life-cycle issues for OEMs who don’t want to continuously redesign the display. In other words, even if you’re successful in designing in the display and can find a stable source, the product will probably have a very short life cycle which will force another redesign.

So what does this mean to me (the Industrial OEM)?

The large numbers of manufacturers who have emerged to support this growth market combined with the massive number of new displays available to the market make selecting the right TFT extremely difficult, especially for engineers splitting time on other components of the new design. I’ve also found that company’s designing solutions with TFTs generally don’t want to redesign after 6-9 months, especially when the initial design took upwards of a year to complete. Unless a company is prepared to invest resources to redesign on a regular interval, they need to lock into a product that incorporates terms and conditions more conducive to industrial applications. In others words, these OEMs need to design with truly industrial panels rather than consumer displays.

So what’s the difference between an “industrial” display and a “consumer” display?

The principal difference between industrial and consumer displays is longevity — an industrial display will be available for a minimum of 3 years (and well beyond that in many cases). These panels are not built on the latest generation fab, which will make them more expensive to manufacturer than panels produce on the latest and greatest fabs; however, this very fact also helps the TFT manufacturer alleviate the pressure to continuously spin their TFT designs. Generally speaking, a good industrial display will incorporate the following key attributes:

• Longevity – look for a 3+ year guarantee for mass production (MP) and take note as to when your desired panel actually went into production
• 6-Month EOL Policy – a 6-month end-of-life (EOL) policy  providing up to 6 months to place a last-time buy (LTB) is extremely important to help bridge the supply chain until the TFT re-design is complete, especially for applications where new certifications are required
• Industrial Roadmap – a strong industrial roadmap with follow-on drop-in replacements for products that are slated for EOL; backward compatibility is extremely important for a quick re-design and most industrial TFT suppliers offer this feature
• Field-Replaceable Backlight – over the life of the panel, a backlight will eventually fade (or fail), so replaceable backlights are a quick, inexpensive way to improve total cost of ownership (TCO) and overall service
• Shock & Vibe – industrial panels are typically much more rugged that consumer panels
• Better Overall Optical Characteristics – industrial panels typically have much improved optical characteristics such as brightness, viewing angle and contrast ratio
• Op Temp – -20 degrees Celsius to +70 degrees Celsius is fast becoming the industrial standard and some suppliers are now offering -30c to +80
• Engineering Support – in addition to the Avnet team, most industrial display manufacturers offer great engineering support state side

A consumer display will always deliver an excellent price point. In some cases, they are half the price of the same diagonal industrial display; but consumer displays can (and typically will) pose the following design challenges:

• Product Quality & Consistency – consumer TFTs tend to be lower quality displays; the factories sort their yields into different grades and the “A” grade panels typically become allocated to customers that demand “A” grade (i.e. the Apple’s and the Motorola’s) or those that will pay the price premium (i.e. the industrial market). Lower grade panels tend to have more pixel defects, are susceptible to color shift, etc. This is not a rule of thumb, but something to be looking for should you not design with an industrial panel.
• Unstable Supply – spikes in global demand could cause your panel to suddenly become unavailable…and this happens quite frequently with “monitor-based” displays (i.e. 15.0”, 17.0”, 19.0”, etc.)
• Rapid EOL – unexpected EOL with limited or no advanced notice always results in a fire drill; not only do you need to secure enough product to bridge the design gap, but you also need to design-in the replacement
• Lack of Backward Compatibility – most
• No Frills – consumer displays are designed for “disposable” applications, so there are no design considerations for replaceable backlights, robust op temps, specialty films, etc.

There are some instances where low-cost consumer TFTs make sense: if you can’t get a product to market profitably (and the TFT is often one of the most expensive components), then there’s no point going to market in the first place. However, we urge customers to also consider total cost of ownership with respects to the entire supply chain. There’s certainly piece of mind knowing that you’ve designed with a solid industrial-grade display and that the industrial display itself will probably be in production much longer than your own product. It’s just one less thing to worry about. 

As a final word about consumer TFTs versus industrial TFTs, take a visit to your local Fry’s Electronics. You can now buy a 24.0” monitor for $129.00; however, if you compare the same monitors side by side, the optical performance is inconsistent. In other words, there are visible differences in the same brand monitor. It’s very inconsistent and representative of lower grade modules.   I personally like the idea of only spending $129.00 on a 24.0” monitor for my wife and kids, but I’m not sure that I want it to be the face of my company’s flag ship product.

So what is Avnet doing to help our customers with Industrial-Grade Displays?

Over the years, we have counseled customers not to design with the lower-cost consumer equivalent, especially if their application truly warranted an industrial-grade display. In one particular instance, however, an Avnet customer opted to design with a consumer TFT for their medical monitor because the consumer display was half the cost of the industrial-grade equivalent. Well, that’s a huge difference. It’s difficult to argue that the customer made the wrong decision. From the customer’s perspective, they could experience 50% fallout and still break even — at least from a purchase price variance (PPV) perspective. However, as predicted, the consumer panel was abruptly EOL’ed after about 6 months of production with no more panels available from the factory. The lack of available product caused a fire drill at the customer to secure all available product in the channel (including the broker channel) in parallel with diverting scarce engineering resources from new projects to the imperiled project’s redesign. 

It’s hard to say what price point warrants the risk to design with a consumer display in a truly industrial application — PPV is critical to keeping your company competitive. Unfortunately, many companies have been brought to their knees after going “lines down” as the result of an unexpected EOL. From our experience, our customers typically opt for the industrial-grade TFT after only one bad experience.

Hopefully this provides a good overview of the industrial market and the value of industrial-grade displays. If you’re planning a new design with a TFT, please enlist the help of Avnet’s talented sales team. For quick reference of what’s available, what’s new and what’s possible, we encourage you to browse our Industrial Display Solutions Guide or view products on our www.embeddedmatrix.com web site. However, our online tools are no substitute for our experienced team of Account Managers, Display Business Development managers and Field Applications Engineers, so please give us a call and get us involved in your next design. Avnet boasts industry-leading display suppliers, services and capabilities and we’re here to help.