HCMS-2919 Avago Technologies US Inc., HCMS-2919 Datasheet - Page 12

• Manufacturer Part Number: HCMS-2919
• Description: LED DISPLAY 5X7 8CHAR 3.8MM BLUE
• Manufacturer: Avago Technologies US Inc.
• Series: HCMS-29xxr

Specifications of HCMS-2919

• Display Type: Alphanumeric
• Millicandela Rating: *
• Size / Dimension: 1.40" L x 0.40" W x 0.20" H (35.6mm x 10.2mm x 5.1mm)
• Color: Blue
• Configuration: 5 x 7
• Voltage - Forward (vf) Typ: *
• Package / Case: 26-DIP
• Number Of Digits/alpha: 8
• Digit/alpha Size: 0.15" (3.8mm)
• Number Of Digits: 8
• Illumination Color: Blue
• Wavelength: 428 nm
• Operating Voltage: 5.5 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Luminous Intensity: 170 ucd
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Common Pin: -
• Lead Free Status / Rohs Status: Details

Appendix A. Thermal Considerations
The display IC has a maximum junction temperature
of 150°C. The IC junction temperature can be calculated
with Equation 1 below.
A typical value for Rθ
for a display mounted in a socket and covered with a
plastic filter. The socket is soldered to a .062 in. thick
PCB with .020 inch wide, one ounce copper traces. PD
can be calculated as Equation 2 below.
Figure 7 shows how to derate the power of one IC
versus ambient temperature. Operation at high
ambient temperatures may require the power per IC
to be reduced. The power consumption can be reduced
by changing either the N, I
Changing V
consumption.
Appendix B. Electrical Considerations
Current Calculations
The peak and average display current requirements
have a significant impact on power supply selection.
The maximum peak current is calculated with Equation
3 below.
The average current required by the display can be
calculated with Equation 4 below.
The power supply has to be able to supply I
transients and supply I
range on V
significantly changing the display brightness.
12
LOGIC
LED
allows noise on this supply without
has very little impact on the power
JA
is 100°C/W. This value is typical
LED
(AVG) continuously. The
PIXEL
, Osc cyc or V
PEAK
LED
.
Figure 7. Maximum power dissipation per IC versus ambient
temperature.
Equation 1:
T
Where:
Equation 2:
P
Where:
Equation 3:
I
Where:
Equation 4:
I
(see Variable Definitions above)
Duty Factor = 1/8 * Osccyc/64
PEAK
LED
J
D
MAX = T
= (N * I
(AVG) = N * I
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Osc cyc = number of ON oscillator cycles per row
= M * 20 * I
T
I
0
I
V
PIXEL
J
I
PEAK
I
MAX = maximum IC junction temperature
LOGIC
LOGIC
25
PIXEL
Rθ
20 = maximum number of LEDs on per IC
M = number of ICs in the system
P
PIXEL
P
T
30
JA
N = number of pixels on (maximum 4 char * 5 * 7 = 140)
A
D
D
A
= maximum instantaneous peak current for the display
= peak current for one LED
+ P
= ambient temperature surrounding the display
= thermal resistance from the IC junction to ambient
= power dissipated by the IC
= total power dissipation
= peak pixel current.
= IC logic current
= logic supply voltage
35
* Duty Factor * V
T
PIXEL
40
A
PIXEL
D
- AMBIENT TEMPERATURE - C
* Rθ
45
* 1/8 * (oscillator cycles)/64
50
JA
55
60
RΘ
LED
65
J-A
) + I
70
= 100 C/W
75
LOGIC
80
85
* V
90
LOGIC