PDSP1880 Datasheet, PDF (14/15 Pages) OSRAM GmbH – Alphanumeric Programmable Display™

PDSP1880, PDSP1881, PDSP1882, PDSP1883, PDSP1884
Electrical and Mechanical Considerations
Voltage Transient Suppression
For best results power the display and the components that inter-
face with the display to avoid logic inputs higher than V_CC. Addi-
tionally, the LEDs may cause transients in the power supply line
while they change display states. The common practice is to place
a parallel combination of a 0.01 µF and a 22 µF capacitor between
V_CC and GND for all display packages.
ESD Protection
The input protection structure of the PDSP188X provides signifi-
cant protection against ESD damage. It is capable of withstanding
discharges greater than 4.0 kV. Take all the standard precautions
normal for CMOS components. These include properly grounding
personnel, tools, tables, and transport carriers that come in con-
tact with unshielded parts. If these conditions are not, or cannot be
met, keep the leads of the device shorted together or the parts in
anti-static packaging.
Soldering Considerations
The PDSP188X can be hand soldered with SN63 solder using a
grounded iron set to 260 °C.
Wave soldering is also possible. Use water soluble organic acid
flux or resin based RMA flux.
A wave temperature of 245 °C ± 5 °C with a dwell between 1.5 sec
to 3.0 sec can be used. Exposure to the wave should not exceed
temperatures above 260 °C for five seconds at 1.59 mm (0.063")
below the seating plane. The packages should not be immersed in
the wave.
Post Solder Cleaning Procedures
The least offensive cleaning solution is hot D.I. water (60 °C) for
less than 15 minutes. Addition of mild saponifiers is acceptable.
Do not use commercial dishwasher detergents.
For faster cleaning, solvents may be used. Exercise care in choos-
ing solvents as some may chemically attack the polycarbonate
package. Maximum exposure should not exceed two minutes at
elevated temperatures. Acceptable solvents are TF (trichorotrifluo-
rethane), and IPA.
Some major solvent manufacturers are: Allied Chemical Corpora-
tion, Specialty Chemical Division, Morristown, NJ;
Baron-Blakeslee, Chicago, IL; Dow Chemical, Midland, MI; E.I.
DuPont de Nemours & Co., Wilmington, DE.
For further information refer to Appnote 19 at www.osram-os.com
An alternative to soldering and cleaning the display modules is to
use sockets. Naturally, 28 pin DIP sockets 7.62 mm (0.300") wide
with 2.54 mm (0.100") centers work well for single displays. Multi-
ple display assemblies are best handled by longer SIP sockets or
DIP sockets when available for uniform package alignment. Socket
manufacturers are Aries Electronics, Inc., Frenchtown, NJ; Garry
Manufacturing, New Brunswick, NJ; Robinson-Nugent, New
Albany, IN; and Samtec Electronic Hardward, New Albany, IN.
Optical Considerations
The 4.70 mm (0.180") high character of the PDSP188X gives
readability up to eight feet. Proper filter selection enhances read-
ability over this distance.
Using filters emphasizes the contrast ratio between a lit LED and
the character background. This will increase the discrimination of
different characters. The only limitation is cost. Take into consider-
ation the ambient lighting environment for the best cost/benefit
ratio for filters.
Incandescent (with almost no green) or fluorescent (with almost no
red) lights do not have the flat spectral response of sunlight. Plas-
tic band-pass filters are an inexpensive and effective way to
strengthen contrast ratios. The PDSP1880 / PDSP1882 are
red / high efficiency red displays and should be matched with a
long wavelength pass filter in the 570 nm to 590 nm range. The
PDSP1883 should be matched with a yellow-green band-pass fil-
ter that peaks at 565 nm. For displays of multiple colors, neutral
density grey filters offer the best compromise.
Additional contrast enhancement is gained by shading the dis-
plays. Plastic band-pass filters with built-in louvers offer the next
step up in contrast improvement. Plastic filters can be improved
further with anti-reflective coatings to reduce glare. The trade-off is
fuzzy characters. Mounting the filters close to the display reduces
this effect. Take care not to overheat the plastic filter by allowing for
proper air flow.
Optimal filter enhancements are gained by using circular polarized,
anti-reflective, band-pass filters. The circular polarizing further
enhances contrast by reducing the light that travels through the filter
and reflects back off the display to less than 1%.
Several filter manufacturers supply quality filter materials. Some of
them are: Panelgraphic Corporation, W. Caldwell, NJ; SGL Homa-
lite, Wilmington, DE; 3M Company, Visual Products Division, St.
Paul, MN; Polaroid Corporation, Polarizer Division, Cambridge,
MA; Marks Polarized Corporation, Deer Park, NY, Hoya Optics,
Inc., Fremont, CA.
One last note on mounting filters: recessing displays and bezel
assemblies is an inexpensive way to provide a shading effect in
overhead lighting situations. Several bezel manufacturers are:
R.M.F. Products, Batavia, IL; Nobex Components, Griffith Plastic
Corp., Burlingame, CA; Photo Chemical Products of California,
Santa Monica, CA; I.E.E.-Atlas, Van Nuys, CA.
2006-03-30
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