Now that you have downloaded the Design Worksheet, you can use it as a guide as you go down this page. When you're finished, you can fill in a Custom Quote Form, or get additional information from our Technical Q & A, or App Notes areas.  This page is rather long, but hang in there, it's very informative.

Type of Display -  Module or Glass only. The most fundamental decision to make is if the display will have the drive circuitry attached (module), or not (glass only). There are advantages and disadvantages to each approach.

When purchasing a custom module, the basic electronic design work will be done by the module supplier. This obviously saves design time and reduces the manpower needed to bring a product to market. You can benefit from the experience we have gained during our previous designs to shorten the design cycle and deliver an optimized product. The major decisions you need to make are the interface type, with standard serial or parallel interfaces being the most common, and the type of backlighting desired. The temperature range, viewing angle, viewing mode, and contrast will need to be considered, but those decisions are common to both approaches.

A glass only design puts the design burden on the end user. You will need to learn a great deal about LCD's in order to complete your design. Luckily, there is an enormous amount of data available to help. In addition to our web site, which supplies most of the basic LCD design information you will need, the suppliers of products associated with LCD's, shown in our Products related to LCD's area have technical information available. We also have a few links to other technical sites, mostly colleges, where you can find an enormous amount of basic information.

The main reasons to buy just the LCD glass are to reduce costs, and provide design flexibility. The total cost of the components necessary to build the drive circuitry is less than the cost of a pre-built module, and as long as you have space on your existing PC board, you won't have to pay for an extra PC board on which to mount the display. By doing a little homework, your design will work just as well as a module, and will allow the flexibility most designers need to adapt their design to ever changing demands.

Technology - TN or STN The type of technology used is determined by the specific performance characteristics of the display you are designing. For a display with a low multiplex rate, i.e. about 32:1 or less (maybe 64:1 under ideal conditions), it is possible to use a standard TN cell and still get an acceptable contrast ratio. Above this level, the contrast falls off quickly.

For displays with multiplex rates greater than 32:1, it has been found that increasing the twist angle to 180 or even 270 degrees, gives superior results. By using a higher twist angle, one can achieve a larger number of multiplexed lines, with a much higher contrast ratio.

By designing displays with these high multiplex rates, a few problems, which could be tolerated at low multiplex rates, come into play. The first problem is the color. Normal STN cells have a greenish background which is objectionable in some designs. The green color can be corrected, however the correction adds cost to the display. The operating temperature range of the displays also suffers, which may require a heater to overcome. The contrast also suffers, and needs to be considered.

Physical Size - In general, the larger the display, the higher the price, as it uses more raw materials. At LXD we usually use a master laminate which is 13.5" x 13.5". We can produce a single display that size, or we can partition the array into hundreds of smaller displays . Our strategy is to maximize the number of individual displays which we can get onto this laminate.  We therefore recommend display sizes that give our customers maximum glass utilization. For example, display widths of 6.75": 4.50", 3.375", 2.70", 2.25" etc., utilize 100% of the 13.5" dimension. (To somewhat confuse matters, we also have a 14" x 16" laminate available for applications which require this larger size.)

In general, if you specify a display size which we feel can be optimized, we will offer you the optimized size, along with the size you have requested.

Viewing Mode - A reflective display has the brightest appearance, with the highest contrast ratio possible. Unfortunately, it will be difficult to read at night or under changing lightning conditions. If your display must be readable under a wide range of lighting conditions, you will generally want a transflective display so that it will look very good in the bright sunlight, but will also be backlightable at twilight and at night. A transmissive display must always have a working backlight, and is therefore unacceptable in applications where power consumption is a problem.

The tradeoff with a transflective display is that it will not look as good as a reflective display during the day, and it will not look as good as a transmissive display at night. It will however enable you to have an acceptable compromise between the two, and provides a very acceptable appearance. A further discussion of viewing modes can be found in or technical Q & A section under  "What is Reflective? Transflective?"

The display can also be negative image or positive image. What is Viewing Mode? in our Technical Q & A area discussed these terms.

Viewing Angle (Direction) - The viewing angle of a part is discussed on the "What is Viewing Angle" page in the Technical Q & A area. In general, the face of the display is divided into quadrants, where a display with a 12:00 viewing angle has optimum contrast from above the normal, and one with optimum contrast below the normal has a 6:00 viewing angle. Similarly, a display which will be viewed mostly from the left or right should have either a 9:30 or 3:30 viewing angle.

Please keep in mind that viewing angle is really not that important for a direct drive display. As a general rule, the higher the multiplex rate, the more important the viewing angle becomes. Also, if your display is going to be viewed by a person wearing polarized sunglasses, you must specify this in the comment section to ensure that the display will not look blank to an observer wearing polarized sunglasses.

If you are unsure what viewing angle your display should have, an e-mail or phone call, 1-(800)786-8710, to our sales department may help. However keep in mind that for quoting purposes, the price of the display will not change much (usually only a few cents) if you guess wrong.

Drive Method - In general, any LCD will have better contrast and viewing angle the lower the mux rate. For parts which are to be viewed under changing lighting conditions, a direct drive part is desirable. Any design which has 14-segment digits will have to be multiplexed to some level., keep the mux rate as low as possible. This item ties into the next item directly, and the two must be balanced to give the best looking display possible. Direct Drive and Multiplexing are discussed extensively in the Technical Q & A, and App Notes Sections.

Indoor / Outdoor - In general, the two things that destroy displays (other than hitting them with a rock) are high heat and humidity. The parts of a display which are most sensitive to heat and humidity are the polarizers. Under extreme conditions, the seals which hold the glass together can fail, however at LXD we have developed materials which effectively eliminate this failure mode. When designing a display for an extremely rugged environment, it is important to make sure that seals will not be a problem. In general then, the environmental considerations comes down to the polarizers.

Displays which will be indoors, or mostly indoors, can use commercial grade polarizers, These polarizers will hold up very well when used in most instrumentation, office and home products, and other applications where the products will be protected from high temperature and humidity.

For harsh environments, a polarizer specifically designed for outdoor, extremely humid conditions should be used. We call these polarizers industrial grade. A wide variety of different outdoor materials is available, with varying contrast, coloration, and efficiency. Because of the many different options, we can supply samples of displays with different polarizers so that you can choose the one which best fits your application.

Another minor point is that you may have to specify that the display must be readable while wearing polarized sunglasses. If this is not specified, because of normal polarizer orientation, the display will appear blank to an observer wearing polarized sunglasses. This point becomes important when designing gas pumps, dashboards, cockpit instrumentation, or marine products.

Fluid Type / Temperature Range - The temperature range of a normal display is usually -40c to +85c when driven in a direct drive mode. Our standard everyday #3 fluid therefore has this temperature range. We also have many other standard fluids, as well as specialty LCD fluids which have operating temperature ranges as low as  -55c and as high as  +122c. Temperature ranges of our standard fluids can be found in our fluid table.

Under extreme conditions, it is possible for a fluid to reach its clearing point, i.e. the point where the display turns completely black because of the heat. While this does not hurt the display, it can be an extreme nuisance. By using our #6 fluid, the clearing point can be raised to +105c, which should be high enough for most   applications. Again, specialty fluids are available to extend the clearing point up to +122C.

Voltage threshold must also be considered when selecting a fluid. The threshold voltages can also be found in our fluid table. These values must be considered when working from low voltage drive circuits, i.e. use our #4 fluid when your power source is a 3V battery, and also at high multiplex rates, where the ratio of on to off voltage comes into play. An discussion of voltage thresholds at high mux rates can be found in our Application Notes section under "Multiplexing an LCD"

Connection Method - For reliability sake, pins are the most desirable connection method available.  In general, if you can keep the mux rate low, we recommend designing a part with pins, even if we have to put them on three sides.Unless your design begs for a heat seal or an elastomer, the only good reason not to use pins is if we cannot fit them all onto the part, i.e., there are more segments to drive than there are pins on the part. At that point the options are to: a) take off the pins and use elastomers or heat seals, or b) multiplex the part, thereby somewhat degrading the contrast and viewing angle. There is a discussion of these options under our Technical Q & A section, entitled  "What is an Elastomer? A Heat Seal? A Pin".

Colors - can be added to an LCD in a number of different ways. Examples of colored displays will be found on our pretty pictures page. I will make a few comments about the cost and appearance of each method:

a) Color Filters - We can add a color decal to the back of the display. This decal can have different colors in different areas so as to give different annunciators different colored backgrounds. This method has the lowest cost, but also gives the dimmest colors.

b) - Similar to the color filters, we can Screen Print different colors onto either the front or rear of the display. Each color can be applied in an intricate pattern, thus giving the same flexibility as the decals but with much brighter colors. This method usually costs more than a color decal, but is the preferred method for most applications.

c) Color Polarizers - We can add a colored polarizer to the front of the display. This method will cause the individual segments to be colored when they are activated, i.e. all segments will be red or green or whatever, on a silver background. This method will add only slightly to the cost of the display. I might add that these colored polarizers are not as efficient as normal polarizers, and the resulting segments do not have the same contrast as a normal black on silver display.

Filters - It is possible to put anti-reflective or anti-glare filters over the front of a display to improve viewability in harsh lighting conditions. These filters are usually bonded directly to the front polarizer of the display.

An anti-glare filter is one that has its front surface either physically or chemically roughened. This surface scatters specular reflections over a wide area. It produces diffuse, bright reflections reducing the overall contrast, but can improve the display readability.

A better, but more expensive solution, is to use a high efficiency anti-reflective material. These materials do not scatter the light like the anti-glare materials, but rather re-direct the light waves so that they continue traveling forward instead of reflecting back toward the observer. New anti-reflective materials can reduce the front surface reflections to less than 0.3% or less.

Finally - You have reached the end of your worksheet, and hopefully have most, if not all, of the information you need to specify a design. You can now fill in a Custom Quote Form, or get additional information from our Technical Q & A, or App Notes areas.