854054AG

www.icst.com/products/hiperclocks.html

REV. A MARCH 29, 2006

10

Integrated

Circuit

Systems, Inc.

ICS854054

4:1

This section provides information on power dissipation and junction temperature for the ICS854054.

Equations and example calculations are also provided.

1. Power Dissipation.

The total power dissipation for the ICS854054 is the sum of the core power.

The following is the power dissipation for V

2. Junction Temperature.

Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad and directly affects the reliability of

The equation for Tj is as follows: Tj =

θ

Tj = Junction Temperature

q

Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)

T

In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance

θ

Assuming a moderate air flow of 200 linear feet per minute and a multi-layer board, the appropriate value is 81.8°C/W per

Table 6 below.

Therefore, Tj for an ambient temperature of 85°C with all outputs switching is:

85°C + 0.312W * 81.8°C/W = 110.5°C. This is below the limit of 125°C.

This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air

flow, and the type of board (single layer or multi-layer).

θθθθθ

JA

FOR

θθθθθ

0

200

500

Single-Layer PCB, JEDEC Standard Test Boards

137.1°C/W

118.2°C/W

106.8°C/W

Multi-Layer PCB, JEDEC Standard Test Boards

89.0°C/W

81.8°C/W

78.1°C/W

NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.