VITESSE

SEMICONDUCTOR CORPORATION

Advance Product Information

VSC7710

Photodetector/Transimpedance Amplifier

Family for Optical Communication

G52139-0, Rev 2.2

Page 5

04/02/01

© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012

Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com

Internet: www.vitesse.com

Thermal Resistance Calculation

In order to relate the junction temperature to an equivalent case temperature, the following thermal charac-

teristics of the package are provided (note that the thermal conductivity is identical for TO-46 and TO-56 pack-

age styles).

Table 5: Thermal Resistance Calculation for TO-56 and TO-46 Packages.

Chip Size

0.168cm x 0.104cm

Thermal Path

Chip Area A

0.066 cm

0.0076 cm

Header thickness (Theader)

(ave. for TO-46 and TO-56)

0.115 cm

Thermal Conductivities

K GaAs

0.55W / cm °C

K epoxy

0.0186W / cm °C

K kovar

0.17W / cm °C

0.066

0.55 x 0.015

= 8

°C/W

==

0.0076

0.0186 x 0.015

= 27.24

°C/W

==

0.12

0.17 x 0.015

= 47

°C/W

==

= Thermal Resistance from Junction to Case = (8 + 27.24 + 47) = 82.24

°C/W

Example:

Temperature rise from junction to case = 0.025A x 5V x 82.24

°C/W = 10.28 °C

θ

GaAs

θ

EXPOXY

θ

KOVAR