ISL59532 Datasheet, PDF (23/24 Pages) Intersil Corporation – 32x32 Video Crosspoint

ISL59532
Where:
• T_JMAX = Maximum junction temperature = 125°C
• T_AMAX = Maximum ambient temperature = 85°C
• θ_JA = Thermal resistance of the package
The maximum power dissipation actually produced by an IC
is the total quiescent supply current times the total power
supply voltage, plus the power in the IC due to the load, or:
n
∑ ^PDMAX ^{= V}S ^{× I}SMAX ⁺
(
V_S
–
V_O
U
T
i
)
×
V_{-----O----U----T----i}
R_Li
i=1
Where:
• V_S = Supply voltage = 5V
• I_SMAX = Maximum quiescent supply current = 700mA
• V_OUT = Maximum output voltage of the application = 2V
• R_LOAD = Load resistance tied to ground = 150
• n = 1 to 32 channels
n
∑ ^PDMAX ^{= V}S ^{× I}SMAX ⁺
(
V_S
–
V_O
U
T
i
)
×
V_{-----O----U----T----i}
R_Li
=
4.8 W
i=1
The required θ_JA to dissipate 4.8W is:
Θ_JA
=
T_{----J---M-----A----X-----–-----}T_{----A---M-----A----X--}
PD_MAX
=
8.33 ( ° C /W )
Table 8 shows θ_JA thermal resistance results with a
Wakefield heatsink and without heatsink and various airflow.
At the thermal resistance equation shows, the required
thermal resistance depends on the maximum ambient
temperature.
TABLE 8. θ_JA THERMAL RESISTANCE [°C/W]
Airflow [LFM]
0
250
500
750
No Heatsink
18
14.3
13.0
12.6
Wakefield
16.0
7.0
6.0
4.7
658-25AB
Heatsink
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23
FN7432.3
July 24, 2006