Application Report
SBAA403 – July 2019

Temp Profile to Maintain Optimum FIT Performance
Russell Hoppenstein

1

Trademarks
All trademarks are the property of their respective owners.

2

Introduction
Temperatures within the product cases of modern telecommunication equipment are increasing due tohigher IC integration, and denser channel configurations. Even with moderately elevated environmental
temperatures, IC junction temperatures are rising to near-maximum limits. Naturally, operation at elevatedjunction temperatures must be controlled to maintain device reliability in the field.

3

Data Sheet Junction Temperature Limits
The data sheet provides a maximum operating junction temperature of 110°C. To prevent any undesireddegradation in reliability, avoid continuously operating at this temperature over extended durations.
As denoted in Equation 1, cumulative operating time between 105°C and 110°C must be less than onethird of the total operating time below 100°C.
110 qC
100 qC1³ T j 105 qC t dT j d 3 u ³ T j min t dT j
(1)
With standard model assumptions, the operation temperature of the device may extend beyond 105°C if
the duration is offset by operating below 100°C for at least three times that amount of time. In a discrete
example, say the device operates at 110 degC for 20% of time. That time must be compensated for byoperating at (or below) 100°C for at least 60% of the time. For the remaining time, the device operates
between 100°C and 105°C.
Figure 1 illustrates an example temp profile that satisfies the previously discussed restriction. The area
under the temp profile curve from 105°C to 110°C (red) is equal to one-third of the area under the curveup to 100°C (blue).
0.07
0.06

Temp <= 100 qC
100 < Temp <= 105 qC
Temp > 105 qC

Time (%)

0.05
0.04
0.03
0.02
0.01
065758595105115
Junction Temperature (qC)

125D001

Figure 1. Example Temperature Profile

4Conclusion
The temp profile provided in this report is strictly for illustrative purposes. It is not intended to be arecommended profile. It is simply an example of an arbitrary temp profile that satisfies the criteria inEquation 1. The model supports operating up to 110°C as long as sufficient time is spent operating atcooler temperatures (< 100°C). However, it is recommended to keep junction temperatures as low as
possible to maintain the best reliability.

SBAA403 – July 2019
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