Operational Lifetime

T

ContinuousJunction Temperature

C

J -

-

o

1000

100

10

1

80

90

100

110

120

130

140

150

160

170

180

T

ContinuousJunction Temperature

C

J -

-

o

100

10

1

0.1

130

150

160

170

180

190

200

140

ADS5463

It is important for applications that anticipate running continuously for long periods of time near the

maximum-rated ambient temperature of +85

°C to consider the data shown in Figure 49 and Figure 50. Referring

to the Thermal Characteristics table, the worst-case operating condition with no airflow has a thermal rise of

23.7

°C/W. At approximately 2.2 W of normal power dissipation, at a maximum ambient of +85°C with no airflow,

the junction temperature of the ADS5463 reaches approximately +85

°C + 23.7°C/W × 2.2 W = +137°C and

therefore the expected lifetime is approximately 8 years due to an electro migration failure and 18 years due to a

wirebonding failure. Being even more conservative and accounting for the maximum possible power dissipation

that is ensured (2.4 W), the junction temperature becomes nearly +142

°C. As Figure 49 and Figure 50 show, this

operating condition limits the expected lifetime of the ADS5463 even more. Operation at +85

°C continuously may

require airflow or an additional heatsink in order to decrease the internal junction temperature and increase the

expected lifetime. An airflow of 250 LFM (linear feet per minute) reduces the thermal resistance to 16.4

°C/W, the

maximum junction temperature to +124

°C and the expected lifetime to over 10 years, assuming a worst-case of

2.4 W and +85

°C ambient. Of course, operation at lower ambient temperatures greatly increases the expected

lifetime.

The ADS5463 performance over temperature is quite good and can be seen starting in Figure 21. Though the

typical plots show good performance at +100

°C, the device is only rated from –40°C to +85°C. For continuous

operation at temperatures near or above the maximum, aside from performance degradation, the expected

primary negative effect is a shorter device lifetime.

Figure 49. Operating Life Derating Chart, Electro

Figure 50. Operating Life Derating Chart, Wirebound

Migration Fail Mode

Voiding Fail Mode

28

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