2–196
SCE5780/1/2/3/4/5
Figure 11. ILL V ariance
Interconnect Considerations
Optimum product performance can be had when the follow-
ing electrical and mechanical recommendations are
adopted. The SCE578X’s IC is constructed in a high speed
CMOS process, consequently high speed noise on the
SERIAL DATA, SERIAL DA TA CLOCK, LOAD and RESET lines
may cause incorrect data to be written into the serial shift r eg-
ister. Adhere to transmission line termination procedures
when using fast line drivers and long cables (>10 cm).
Good ground (pin 2) and power supply decoupling (pins 9
and 10) will insure that Icc (<800 mA peak) switching cur-
rents do not generate localized ground bounce. Therefore it
is recommended that each display package use a 0.1µF and
20 µF tanulum capacitor between VCC and ground.
When the internal MUX Clock is being used connect the CLK-
SEL pin to VCC. In those applications where RESET will not be
connected to the system’s reset control, it is recommended
that this pin be connected to the center node of a series 0.1,
µF and 100 KΩ RC network. Thus upon initial power up the
RESET will be held low for 10 ms allowing adequate time for
the system power supply to stabilize.
ESD Protection
The input protection structure of the SCE578X provides sig-
nificant protection against ESD damage. It is capable of with-
standing discharges greater than 2 KV. Take all the standard
precautions, normal for CMOS components. These include
properly grounding personnel, tools, tables, and transport
carriers that come in contact 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 SCE578X can be hand soldered with SN63 solder using
a grounded iron set to 260°C.
Wave soldering is also possible following these conditions:
Preheat that does not exceed 93°C on the solder side of the
PC board or a package surface temperature of 85°C. Water
soluble organic acid flux (except carboxylic acid) or resin-
based RMA flux without alcohol can be used.
Wave temperature of 245°C ±5°C with a dwell between 1.5
sec. to 3.0 sec. Exposure to the wave should not exceed tem-
peratures above 260°C for five seconds at 0.063" below the
seating plane. The packages should not be immersed in the
wave.
Vcc
Icc
0
0.2
0.4
0.6
0.8
1
1.2
1.4
3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50
Post Solder Cleaning Procedures
The least offensive cleaning solution is hot D.I. water (60°C)
for less than 15 minutes. Addition of mild saponifers is
acceptable. Do not use commercial dishwasher detergents.
For faster cleaning, solvents may be used. Exercise care in
choosing solvents as some may chemically attack the nylon
package. For further information refer to Appnotes 18 and 19
in the current Siemens Optoelectronic Data Book. See App-
note 19, Table 1, “Displays–Group 2.”
An alternative to soldering and cleaning the display modules
is to use sockets. Naturally, 14 pin DIP sockets .300" wide
with .100" centers work well for single displays. Multiple dis-
play assemblies are best handled by longer SIP sockets or
DIP sockets when available for uniform package alignment.
Socket manufacturers are Aries Electronics, Inc., French-
town, NJ; Garry Manufacturing, New Brunswick, NJ; Robin-
son-Nugent, New Albany, IN; and Samtec Electronic
Hardward, New Albany, IN.
For further information refer to Appnote 22 in the current Sie-
mens Optoelectronic Data Book.
Optical Considerations
The 0.180" high character of the SCE578X gives readability
up to five feet. Proper filter selection enhances readability
over this distance.
Using filters emphasizes the contrast ratio between a lit LED
and the character background. This will increase the dis-
crimination of differ ent characters. The only limitation is cost.
Take into consideration 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. Plastic band-pass filters are an inexpensive and
effective way to str engthen contrast ratios. The SCE5780 is a
red display and should be used with long wavelength pass
filter having a sharp cut-off in the 600 nm to 620 nm range.
The SCE5782 is a high efficiency red display and should be
used with long wavelength pass filter having a sharp cut-off
in the 570 nm to 600 nm range. The SCE5784 is a high effi-
ciency green display and should be used with long wave-
length pass filter that peaks at 565 nm.
Additional contrast enhancement is gained by shading the
displays. 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 r eflects 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 Homalite, Wilmington, DE; 3M Company, Visual
Products Division, St. Paul, MN; Polaroid Corporation,