VITESSE
SEMICONDUCTOR CORPORATION
Datasheet
2.5 Gb/s 16-Bit Multiplexer/
Demultiplexer Chipset
VSC8061/VSC8062
The worst case temperature rise from case to ambient is given by the equation:
∆T = P(MAX)(θSA + θCS
)
where:
θSA Theta sink to ambient
θCS Theta case to sink
ΤA(MAX) Air temperature, user supplied (typically 55o C)
ΤC(MAX) Case temperature (85oC for Industrial range)
∆TTC - TA
P(MAX) Power (2.0 W for VS8061)
TC – TA
P = ------ = -----------------------
Σθ SA + θCS
∆T
θ
∆T
θSA = ------ – θCS
P
Ιf TA = 55o C and θCS (user supplied) is typically 0.6o C/W,
(85 – 55)°C
θSA = ----------------------------- – 0 . 6 °C ⁄ W
2W
θSA = 14.4°C ⁄ W
Therefore, to maintain the proper case and junction temperature, a heat sink with a θSA of 14.4o C/W or less
must be selected at the appropriate air flow.
Note: the heat spreader is tied to VEE in both the VS8061 and VS8062.
G52069-0, Rev. 4.1
6/22/99
VITESSE SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896
Page 17
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