ICS841S012DKI REVISION A JULY 20, 2009

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©2009 Integrated Device Technology, Inc.

ICS841S012DI Data Sheet

CRYSTAL-TO-0.7V DIFFERENTIAL HCSL/LVCMOS FREQUENCY SYNTHESIZER

θθθθθ

2. Junction Temperature.

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

The equation for Tj is as follows: Tj =

θ

Tj = Junction Temperature

θ

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 1 meter per second air flow and a multi-layer board, the appropriate value is 27.5°C/W per Table 7.

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

85°C + 1.396W * 27.5°C/W = 123.4°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 (multi-layer).

θθθθθ

0

1

2.5

Multi-Layer PCB, JEDEC Standard Test Boards

31.4°C/W

27.5°C/W

24.6°C/W