26

603 Hardware Specifications

Loctite Corporation

860-571-5100

1001 Trout Brook Crossing

Rocky Hill, CT 06067

AI Technology (e.g., EG7655)

609-882-2332

1425 Lower Ferry Rd

Trent, NJ 08618

The following section provides a heat sink selection example using one of the commercially available heat

sinks.

1.8.6.3 Heat Sink Selection Example

For preliminary heat sink sizing, the die-junction temperature can be expressed as follows:

Tj = Ta + Tr + (θjc + θint + θsa) * Pd

Where:

Tj is the die-junction temperature

Ta is the inlet cabinet ambient temperature

Tr is the air temperature rise within the computer cabinet

θ

jc is the die junction-to-case thermal resistance

θ

int is the adhesive or interface material thermal resistance

θ

sa is the heat sink base-to-ambient thermal resistance

Pd is the power dissipated by the device

During operation the die-junction temperatures (Tj) should be maintained less than the value specified in

Table 2. The temperature of the air cooling the component greatly depends upon the ambient inlet air

temperature and the air temperature rise within the electronic cabinet. An electronic cabinet inlet-air

temperature (Ta) may range from 30 to 40 °C. The air temperature rise within a cabinet (Tr) may be in the

range of 5 to 10

°C. The thermal resistance of the thermal interface material (θ

int) is typically about

1

°C/W. Assuming a T

a of 30 °C, a Tr of 5 °C a CQFP package θjc = 2.2 °C/W, and a power consumption

(Pd ) of 3.0 W, the following expression for Tj is obtained:

Die-junction temperature: Tj = 30 °C + 5 °C + (2.2 °C/W + 1.0 °C/W + Rsa) * 3.0 W

For a Thermalloy heat sink #2328B, the heat sink-to-ambient thermal resistance (Rsa) versus airflow

velocity is shown in Figure 16.

AR

CH

IVE

D B

Y F

RE

ES

CA

LE

SE

MI

CO

ND

UC

TO

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INC

.