8
Electrical
These display devices are composed of eight light emitting
diodes, with light from each LED optically stretched to
form individual segments and a decimal point.
The devices utilize LED chips which are made from GaAsP
on a transparent GaP substrate.
These display devices are designed for strobed operation.
The typical forward voltage values, scaled from Figure 4,
should be used for calculating the current limiting resistor
value and typical power dissipation. Expected maximum
VF values, for the purpose of driver circuit design and
maximum power dissipation, may be calculated using the
following VF MAX models:
VF MAX = 2.15 V + IPEAK (13.5 :)
For: IF ≥ 30 mA
VF MAX = 1.9 V + IDC (21.8 :)
For: 10 mA ≤ IF ≤ 30 mA
Temperature derated strobed operating conditions are
obtained from Figures 1 and 2. Figure 1 relates pulse
duration (tp), refresh rate (f), and the ratio of maxi mum peak
current to maxi mum dc current (IPEAK MAX/IDC MAX). Figure
2 presents the maximum allowed dc current vs. ambient
temperature. Figure 1 is based on the principle that the peak
junc tion temperature for pulsed operation at a specied
peak current, pulse duration and refresh rate should be
the same as the junction temperature at maximum DC
operation. Refresh rates of 1 kHz or faster minimize the
pulsed junction heating eect of the device resulting in the
maximum possible time average luminous intensity.
The time average luminous inten sity can be calculated
knowing the average forward current and relative ef-
ciency characteristic, KPEAK, of Figure 3. Time average
luminous intensity for a device case temperature of 25°C,
IV (25°C), is calculated as follows:
I
AVG
IV (25°C) = [ ] [KPEAK] [IV DATA SHEET]
20 mA
Example: For HDSP-4030 series
KPEAK = 1.00 at IPEAK = 100 mA.
For DF = 1/5:
20 mA
IV (25°C) = [ ] [1.00] [4.5 mcd]
20 mA
= 4.5 mcd/segment
The time average luminous inten sity may be adjusted for
operat ing junction temperature by the following expo-
nential equation:
IV (TJ) = IV (25°C) e[k(TJ + 25°C)]
where TJ = T
A + PDt3ɁJ-A
Device K
-3900 -0.0131/°C
-4030/-4130/-5730/-4200 -0.0112/°C
Mechanical
These devices are constructed utilizing a lead frame in a
standard DIP package. The LED dice are attached directly
to the lead frame. Therefore, the cathode leads are the
direct thermal and mechanical stress paths to the LED
dice. The absolute maximum allowed junction tempera-
ture, TJ MAX, is 105°C. The maximum power ratings have
been established so that the worst case VF device does not
exceed this limit.
Worst case thermal resistance pin-to-ambient is 400°C/W/
Seg when these devices are soldered into minimum
trace width PC boards. When installed in a PC board that
provides RTPIN-A less than 400°C/W/Seg these displays
may be operated at higher average currents as shown in
Figure 2.
Optical
The radiation pattern for these devices is approximately
Lam bertian. The luminous sterance may be calculated
using one of the two following formulas.
I
v (cd)
LV (cd/m2) =
A (m2)
SIv (cd)
LV (footlamberts) =
A (ft2)
Device
Area/Seg.
mm2
Area/Seg.
in2
-4030 2.5 0.0039
-4130 4.4 0.0068
-5730 8.8 0.0137
-3900/-4200 14.9 0.0231