11

2016© Integrated Device Technology, Inc.

Revision E, January 5, 2016

8545 Datasheet

Power Considerations

This section provides information on power dissipation and junction temperature for the 8545.

Equations and example calculations are also provided.

1.

Power Dissipation.

The total power dissipation for the 8545 is the sum of the core power plus the power dissipated in the load(s).

NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.

•

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 device. The

maximum recommended junction temperature is 125°C.

Tj = Junction Temperature



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

flow of 200 linear feet per minute and a multi-layer board, the appropriate value is 66.6°C/W per Table 6 below.

Therefore, Tj for an ambient temperature of 70°C with all outputs switching is:

70°C + 0.173W * 66.6°C/W = 81.5°C. This is well 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).



Linear Feet per Minute

0

200

500

Single-Layer PCB, JEDEC Standard Test Boards

114.5°C/W

98.0°C/W

88.0°C/W

Multi-Layer PCB, JEDEC Standard Test Boards

73.2°C/W

66.6°C/W

63.5°C/W