ICS831752I Data Sheet

CLOCK SWITCH FOR ATCA/AMC AND PCIe APPLICATIONS

ICS831752AGI REVISION A JUNE 28, 2012

13

©2012 Integrated Device Technology, Inc.

Power Considerations

This section provides information on power dissipation and junction temperature for the ICS831752I.

Equations and example calculations are also provided.

1.

Power Dissipation.

The total power dissipation for the ICS831752I is the sum of the core power plus the analog power plus the power dissipated in the load(s).

•

Power dissipation for the FCLK, nFCLK input internal 50ohm termination. Assume the FCLK, nFCLK input is driven by a HCSL driver. Logic

High input current ~ 17mA. Logic low current ~ 0mA.

•

2.

Junction Temperature.

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

maximum recommended junction temperature is 125°C. Limiting the internal transistor junction temperature, Tj, to 125°C ensures that the bond

wire and bond pad temperature remains below 125°C.

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)

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

θ

a multi-layer board, the appropriate value is 81.2°C/W per Table 6 below.

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

85°C + 0.236W * 81.2°C/W = 104.2°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).

θ

Meters per Second

01

2.5

Multi-Layer PCB, JEDEC Standard Test Boards

81.2°C/W

73.9°C/W

70.2°C/W