AS1100PL datasheet(10/12 Pages) AMSCO

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Data Sheet AS1100

Revision 1.32, Oct. 2004

Page 10 of 12

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

Millimeters

Dim Min

Max

Min

Max

0.093 0.104 2.35

2.65

A1 0.004 0.012 0.10

0.30

0.014 0.019 0.35

0.49

C 0.009 0.013 0.23

0.32

D 0.598 0.614 15.20

15.60

0.050

1.27

0.291 0.299 7.40

7.60

H 0.394 0.419 10.00

10.65

0.016 0.050 0.40

1.27

Figure 4: SOIC-24 package dimensions

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