Data Sheet AS1100
Computing Power Dissipation
The upper limit for power dissipation (PD) for the AS1100 is determined from the following equation:
PD = (VDD x 0.5mA) + (VDD - VLED)(DUTY x ISEG x N)
where:
VDD = supply voltage
DUTY = duty cycle set by intensity register
N = number of segments driven (worst case is 8)
VLED = LED forward voltage
ISEG = segment current set by RSET
Dissipation Example:
ISEG = 40mA, N = 8, DUTY = 31/32, VLED = 1.8V at 40mA, VDD = 5.25V
PD = 5.25V(0.5mA) + (5.25V - 1.8V)(31/32 x 40mA x 8) = 1.07W
Thus, for a PDIP package θJA = +75°C/W (from Table 13), the maximum allowed ambient temperature TA is given by:
TJ,MAX = TA + PD x θJA = 150°C = TA +1.07W x 75°C/W.
where TA = +69.7°C.
The TA limit for SO Packages in the dissipation example above is +59.0°C.
Package Information
Inches
Dim Min Max Min
0.093 0.104 2.35
A1 0.004 0.012 0.10
Millimeters
Max
2.65
0.30
0.49
0.32
A
B
C
D
e
0.014 0.019 0.35
0.009 0.013 0.23
0.598 0.614 15.20 15.60
0.050
1.27
7.60
E
H
L
0.291 0.299 7.40
0.394 0.419 10.00 10.65
0.016 0.050 0.40 1.27
Figure 4: SOIC-24 package dimensions
Revision 1.32, Oct. 2004
Page 10 of 12
AMSCO [ AMS(艾迈斯) ]
