83052AGILFT Datasheet, PDF (12/17 Pages) Integrated Device Technology – 2 1 single-ended multiplexer

ICS83052I Data Sheet
2:1, SINGLE ENDED MULTIPLEXER
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, 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 * Pd_total + T
JA
A
Tj = Junction Temperature
θ = Junction-to-Ambient Thermal Resistance
JA
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
T = Ambient Temperature
A
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θ must be used.
JA
Assuming no air flow and a multi-layer board, the appropriate value is 101.7°C/W per Table 6.
Therefore, Tj for an ambient temperature of 85°C with all outputs switching is:
85°C + 0.221W * 101.7°C/W = 107.4°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).
TABLE 6. θ VS. AIR FLOW TABLE FOR 8 LEAD TSSOP
JA
Meters per Second
θ_JA BY Velocity
0
Multi-Layer PCB, JEDEC Standard Test Boards
101.7°C/W
1
90.5°C/W
2.5
89.8°C/W
ICS83052I REVISION B DECEMBER 8, 2011
12
©2011 Integrated Device Technology, Inc.