As an engineer, my two greatest fears are running out of coffee and the uncertainty of the End-of-Life (EOL) issue.
I handle my coffee fears by hording bags of Caribou and Pete's coffee in a safe, bolted to my desk, protected by a motion sensor. It's also good to have a UPS (uninterruptable power supply) with which to power the coffee grinder in case of some national emergency and/or power grid failure.
My second fear, the EOL issue, is a bit scarier since it is beyond my control.
No, this is not an article regarding what happens to engineers after they bite the dust and travel to that great design review in the sky. As important as that question is, my goal is to address the serious question that many design engineers have asked since the
dawn of time creation of LCDs (liquid crystal displays):
Can a LCD supplier guarantee that their LCD will not go End of Life (EOL) in the next five, ten, or fifteen years?
No pressure, or anything, but Engineers are expected to design products that keep technology moving forward. The quickest way for an engineer to fall out of favor is to select a component that goes EOL just as their company begins production. (I think there is an organization called 'Amnesty International for engineers,' to hide miscreant engineers when this happens. If not, one should be started. Let me know if you want to be a charter member. I'll throw in a bag of coffee.)
Woe betide the one who selects a component that goes EOL (Source: Adobe Stock Photos)
The thing is that EOL is a common problem in the LCD world, with some display technologies more prone to being discontinued than others.
And so we return to the question. “Is it possible for an LCD supplier to can guarantee production of a particular display for five, ten, or fifteen years?'
I want to address this difficult question with a straightforward answer: “Yes” and “No.”
Why do LCDs go EOL?
There are many companies that assemble LCD modules, but only a few companies that manufacture the glass necessary to actually build the displays. As it is with most companies, they deploy their limited resources to build was is most profitable. In doing so, they will shift resources from a current product line to another. This increases lead time and, in many cases, causes older display technologies to be discontinued.
All of which leads to the $64,000 question: “Which display technologies are prone to reach EOL before others?”
Which LCD technologies are prone to go EOL?
There are five main display technologies used to provide information to the end user, each with its own probability of going EOL. Let's start with the technology with the highest probability of going EOL and working our way to the technology with the least probability of going EOL.
#1: OLED (Probability of EOL = High): Organic Light Emitting Diodes (OLEDs) are one of the most popular display technologies available, and the most prone to go EOL.
OLED technologies are the most prone to go EOL (Source: Adobe Stock Photos)
OLED features include the following:
- Over 64K+ unique colors.
- Very fast refresh rate.
- Ultra-sharp contrast.
- Thin (almost anorexic).
- The ability to operate down to -40°C (colder if the module is leaning against a hot cup of dark roast coffee [no cream] and a cinnamon danish fresh out of the microwave).
The challenge with OLEDs is, paradoxically, linked to their popularity: a few large manufacturers of consumer products demand such high volumes that they pinch the limited supply for smaller OEMs needing lower quantities (e.g., 500, 1K, 5K, and 10K).
Suggestions: If you don't require a multi-color display, go with a VATN (Vertically Aligned Twisted Nematic). These have a low probability of going bye-bye (where “bye-bye” is another technical engineering term for EOL) and can be fully customized for a low NRE (tooling) cost.
TFT (Probability of EOL = Medium): Thin Film Transistor (TFT) technology has been in use for many years.
4.3″ TFT display (Source: focuslcds.com)
TFT features include the following:
- Over 64K+ unique colors.
- Fast refresh rate for videos.
- Ability to increase brightness for sunlight readability.
The ability to operate down to -30°C.
There is an abundance of TFT suppliers, which means that a few large OEMS do not upset the supply to smaller OEMs. TFT manufactures have been building the same boring 3.5″ and 4.3″ TFTs for the past few years with very little reason to discontinue.
Lead times for TFTS are increasing, but they are not being discounted at the same rate as OLEDs.
One challenge with TFTS and OLEDs is that their controllers tend to be discontinued every few years. When this happens, the supplier will offer an alternative that may not be 100% compatible, in which case two possible solutions are as follows:
- Rewrite code.
- The dreaded and expensive LTB (last time buy).
Beware! Purchasing people can turn very, very, ugly [photo of someone turning ugly] and may turn on you when mentioning the words 'last-time-buy.' After breaking this exciting news to them, keep looking behind you when leaving the building or walking down any dark hall ways. Also, check to make sure the elevator is empty before entering.
The purchasing department can turn ugly when they hear the term LTB (Source: pixabay.com)
One low-cost solution for a discontinued controller/driver is for your LCD supplier to purchase a few years' worth of just the controller chips. The chips are a fraction of the cost compared of the module and a good supplier will hold inventory until required.
#3: Monochrome Character Displays (Probability of EOL = Low): There are a tremendous number of applications that employ simple monochrome (single color) character displays
Monochrome character display (Source: focuslcds.com)
Monochrome character display features include:
- Excellent in sunlight.
- Low-cost to customize.
- Standard sizes that have been in use since Noah invited the animals onto his ark.
- In stock with a short lead-time for high volumes.
Pass me another fermented coconut (Source: Adobe Stock Photos)
Characters displays are rarely discontinued, but if it does turn out that your current supplier decides to move operations to a beach in the Bahamas where the Wi-Fi signal is weak but the little drinks with an umbrella are strong, then they are easy to cross over to another supplier.
#4: Monochrome Segment Displays (Probability of EOL = Very Low): Monochrome segment displays can be found on such items as gas pumps, digital watches, and thermometers.
Monochrome segment displays at gas station (Source: Adobe Stock Photos)
Monochrome segment display features include:
- Excellent in sunlight.
- Very low-cost to customize.
- Very low power.
- Very low unit cost.
These segment displays employ a simple design consisting of two pieces of glass, some liquid, and a few metal pins. Most modules do not contain a controller since the interface is 4:1 multiplexer and direct drive. There is very little probability of EOL since there are many glass suppliers in this market.
Although this is one of the oldest technologies in production, segments are still one of the most popular. I would hazard to guess that 99.999999% of all new designs using a segment displays are custom, and why not? For around only $1,000, the engineers get the size, icons, and color they want.
#5: Cardboard and Crayons (Probability of EOL = Zero): OK, you may not think of these as LCDs, but they do display information. In this case, LCD stands for “Large Crayon Display” or “Large Cardboard Display.”
Large crayon display (Source: Adobe Stock Photos)
This technology was in use before there were analog-to-digital converters, semiconductor memories, or printed circuit boards. Best of all, there is no fancy-smancy interface to try to figure out.
Cardboard and crayon display features include the following:
- Operates way below -40°C (also can be used to start a fire for warmth if stranded in a snow storm).
- Requires no power.
- No glass to break or scratch.
- Lead-time of seconds, not weeks or months.
It's safe to say that this form of display technology is a safe solution when upper management demands a display that will be in production for the next ten, fifteen, or even fifty years.
As always, the specifiers and developers of an embedded system have to make various tradeoffs and consider a wide range of factors that influence the design. One of these considerations is the display. OLED and TFT color displays offer a lot of advantages; as a general rule, however, monochrome displays have less probability of going EOL.