Data Sheet

Broadcom AV02-0629EN
17
HDSP-210x/-211x/-250x Series Data Sheet Eight-Character 5 mm and 7 mm Smart Alphanumeric Displays
Mechanical and Electrical Considerations
The HDSP-210X/-211X/250X are 28-pin dual-in-line packages with 26 external pins. The devices can be stacked
horizontally and vertically to create arrays of any size. The HDSP-210X/-211X/-250X are designed to operate continuously
from –45°C to +85°C with a maximum of 20 dots on per character at 5.25 V. Illuminating all thirty-five dots at full brightness
is not recommended.
The HDSP-210X/-211X/250X are assembled by die attaching and wire bonding 280 LED chips and a CMOS IC to a thermally
conductive printed circuit board. A polycarbonate lens is placed over the PC board creating an air gap over the LED wire
bonds. A protective cap creates an air gap over the CMOS IC. Backfill epoxy environmentally seals the display package.
This package construction makes the display highly tolerant to temperature cycling and allows wave soldering.
The inputs to the IC are protected against static discharge and input current latchup. However, for best results standard
CMOS handling precautions should be used. Prior to use, the HDSP-210X/-211X/-250X should be stored in antistatic tubes
or in conductive material. During assembly, a grounded conductive work area should be used, and assembly personnel
should wear conductive wrist straps. Lab coats made of synthetic material should be avoided since they are prone to static
buildup. Input current latchup is caused when the CMOS inputs are subjected to either a voltage below ground (V
IN
< ground)
or to a voltage higher than V
DD
(V
IN
> V
DD
) and when a high current is forced into the input. To prevent input current latchup
and ESD damage, unused inputs should be connected either to ground or to VDD. Voltages should not be applied to the
inputs until VDD has been applied to the display.
Thermal Considerations
The HDSP-210X/-211X/-212X/250X have been designed to provide a low thermal resistance path for the CMOS IC to the
26 package pins. Heat is typically conducted through the traces of the printed circuit board to free air. For most applications
no additional heat sinking is required.
Measurements were made on a 32 character display string to determine the thermal resistance of the display assembly.
Several display boards were constructed using 0.062 in. thick printed circuit material, and one ounce copper 0.020 in. traces.
Some of the device pins were connected to a heat sink formed by etching a copper area on the printed circuit board
surrounding the display. A maximally metallized printed circuit board was also evaluated. The junction temperature was
measured for displays soldered directly to these PC boards, displays installed in sockets, and finally displays installed in
sockets with a filter over the display to restrict airflow. The results of these thermal resistance measurements, Rθ
J-A
are
shown in Thermal Resistance (θ
JA
) Using Various Amounts of Heatsinking Material and include the effects of Rθ
J-C
.
Ground Connections
Two ground pins are provided to keep the internal IC logic ground clean. The designer can, when necessary, route the analog
ground for the LED drivers separately from the logic ground until an appropriate ground plane is available. On long
interconnections between the display and the host system, the designer can keep voltage drops on the analog ground from
affecting the display logic levels by isolating the two grounds.
The logic ground should be connected to the same ground potential as the logic interface circuitry. The analog ground and
the logic ground should be connected at a common ground which can withstand the current introduced by the switching LED
drivers. When separate ground connections are used, the analog ground can vary from –0.3V to +0.3V with respect to the
logic ground. Voltage below –0.3V can cause all dots to be on. Voltage above +0.3V can cause dimming and dot mismatch.