AS1106WL 데이터 시트보기 (PDF) - austriamicrosystems AG
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AS1106WL Datasheet PDF : 20 Pages
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AS1106, AS1107
Data Sheet
austriamicrosystems
Calculating Power Dissipation
Table 21. RSET vs. Segment Current and LED Forward Voltage, VDD = 4.0V (Continued)
ISEG (mA)
20
10
1.5
17.7kΩ
36.89kΩ
2.0
17.3kΩ
35.7kΩ
VLED(V)
2.5
16.6kΩ
34.5kΩ
3.0
15.6kΩ
32.5kΩ
3.5
13.6kΩ
29.1kΩ
Table 22. RSET vs. Segment Current and LED Forward Voltage, VDD = 5.0V
ISEG (mA)
40
30
20
10
1.5
11.35kΩ
15.4kΩ
23.6kΩ
48.9kΩ
2.0
11.12kΩ
15.1kΩ
23.1kΩ
47.8kΩ
VLED (V)
2.5
3.0
10.84kΩ
10.49kΩ
14.7kΩ
14.4kΩ
22.6kΩ
22kΩ
46.9kΩ
45.4kΩ
3.5
10.2kΩ
13.6kΩ
21.1kΩ
43.8kΩ
4.0
9.9kΩ
13.1kΩ
20.2kΩ
42kΩ
Table 23. Package Thermal Data
Package
24 Narrow DIP
24 Wide SOIC
Thermal Resistance (ΘJA)
+75°C/W
+85°C/W
Calculating Power Dissipation
The upper limit for power dissipation (PD) for the AS1106/AS1107 is determined from the following equation:
PD = (VDD x 1mA) + (VDD - VLED)(DUTY x ISEG x N)
Where:
VDD is the supply voltage.
DUTY is the duty cycle set by intensity register (page 11).
N is the number of segments driven (worst case is 8)
VLED is the LED forward voltage
ISEG = segment current set by RSET
Dissipation Example:
(EQ 1)
ISEG = 40mA, N = 8, DUTY = 31/32, VLED = 1.8V at 40mA, VDD = 5.25V
PD = 5.25V(1mA) + (5.25V - 1.8V)(31/32 x 40mA x 8) = 1.075W
Thus, for a PDIP package ΘJA = +75°C/W (from Table 23), the maximum allowed TAMB is given by:
(EQ 2)
(EQ 3)
TJ,MAX = TAMB + PD x ΘJA = 150°C = TAMB +1.07W x 75°C/W
Where:
TAMB = +69.4°C.
The TAMB limit for SO Packages in the dissipation example above is +58.6°C.
(EQ 4)
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Revision 2.2
14 - 20
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