ICS8430S10I-03 Datasheet, PDF (23/31 Pages) Integrated Device Technology – Clock Generator for Cavium Processors

ICS8430S10I-03 Data Sheet
CLOCK GENERATOR FOR CAVIUM PROCESSORS
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_JA * Pd_total + T_A
Tj = Junction Temperature
θ_JA = Junction-to-Ambient Thermal Resistance
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
T_A = Ambient Temperature
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θ_JA must be used. Assuming no air flow and
a multi-layer board, the appropriate value is 33.1°C/W per Table 7A below.
Therefore, Tj for an ambient temperature of 85°C with all outputs switching is:
85°C + 0.671W * 33.1°C/W = 107.2°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.
Table 7A. Thermal Resistance θ_JA for 48 Lead TQFP, EPAD Forced Convection
θ_JA Vs. Air Flow
Meters per Second
0
1
Multi-Layer PCB, JEDEC Standard Test Boards
33.1°C/W
27.2°C/W
2.5
25.7°C/W
ICS8430S10BYI-03 REVISION A FEBRUARY 22, 2011
23
©2011 Integrated Device Technology, Inc.