83052I Data Sheet
©2015 Integrated Device Technology, Inc December 15, 201512
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 = θJA * Pd_total + TA
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 θJA
must be used. Assuming
no air fl ow 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 fl ow,
and the type of board (multi-layer).
TABLE 6. θ
JA
VS. AIR FLOW TABLE FOR 8 LEAD TSSOP
θ
JA
BY Velocity
Meters per Second 0 1 2.5
Multi-Layer PCB, JEDEC Standard Test Boards 101.7°C/W 90.5°C/W 89.8°C/W
