16
Figure 5.
Appendix E. Display Brightness
Two ways have been shown to control the brightness of this LED display: setting the peak current and setting the
duty factor. Both values are set in Control Word 0. To compute the resulting display brightness when both PWM
and peak current control are used, simply multiply the two relative bright ness factors. For example, if Control
Register 0 holds the word 1001101, the peak current is 73% of full scale (BIT D
5
= L, BIT D
4
= L) and the PWM is
set to 60% duty factor (BIT D
3
= H, BIT D
2
= H, BIT D
1
= L, BIT D
0
= H). The resulting brightness is 44% (.73 x .60
= .44) of full scale.
The temperature of the display will also aect the LED bright ness as shown in Figure 5.
Intensity Bin Limits for HCMS-29xx (except for HCMS-29x5)
BIN
Intensity Range (mcd)
Min. Max.
D 1.18 2.07
E 1.78 3.13
F 2.70 4.64
G 4.00 7.00
H 6.00 10.50
I 9.00 15.75
J 13.58 23.88
K 20.59 36.03
L 31.06 54.35
Note:
Test conditions as specied in Optical Characteristic table.
Intensity Bin Limits for HCMS-29x5
BIN
Intensity Range (mcd)
Min. Max.
H 6.00 10.50
I 9.00 15.75
J 13.58 23.88
K 20.59 36.03
L 31.06 54.35
M 46.45 80.41
Note:
Test conditions as specied in Optical Characteristic table.
Appendix D. Refresh Circuitry
This display driver consists of 20 one-of-eight column decoders and 20 constant current sources, 1 one-of-eight
row decoder and eight row sinks, a pulse width modulation control block, a peak current control block, and the
circuit to refresh the LEDs. The refresh counters and oscillator are used to synchronize the columns and rows.
The 160 bits are organized as 20 columns by 8 rows. The IC illuminates the display by sequentially turning ON
each of the 8 row-drivers. To refresh the display once takes 512 oscillator cycles. Because there are eight row driv-
ers, each row driver is selected for 64 (512/8) oscillator cycles. Four cycles are used to briey blank the display
before the following row is switched on. Thus, each row is ON for 60 oscillator cycles out of a possible 64. This
corresponds to the maximum LED on time.
RELATIVE LUMINOUS INTENSITY
(NORMALIZED TO 1 AT 25 °C)
YELLOW
HER/ORANGE
0.2
-55
T
A
– AMBIENT TEMPERATURE – °C
3.0
2.6
2.2
1.8
1.4
1.0
0.6
856545255-15-35
GREEN
DEEP RED
