Clock Input

LVDS Data Output

Analog Input

ADS5474

SLAS525C – JULY 2007 – REVISED JANUARY 2016

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10.2 Layout Example

*Solid Black is top layer ground fill

Figure 47. ADS5474 Board Layout

10.3 Thermal Considerations

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 48. Referring to the Thermal Information

table, the worst-case operating condition with no airflow has a thermal rise of 23.7°C/W. At approximately 2.5 W

of normal power dissipation, at a maximum ambient of 85°C with no airflow, the junction temperature of the

ADS5474 device reaches approximately 85°C + (23.7°C/W × 2.5 W) = +144°C. Being even more conservative

and accounting for the maximum possible power dissipation that is ensured (2.797 W), the junction temperature

becomes nearly 150°C. As Figure 48 shows, this performance limits the expected lifetime of the ADS5474

device. Operation at 85°C continuously can require airflow or an additional heatsink in order to decrease the

internal junction temperature and increase the expected lifetime (because of electromigration failures). An airflow

of 250 LFM (linear feet per minute) reduces the thermal resistance to 16.4°C/W and, therefore, the maximum

junction temperature to 131°C, assuming a worst-case of 2.797 W and 85°C ambient.

The ADS5474 device 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, the expected primary negative effect is a shorter device

lifetime because of the electromigration failures at high junction temperatures. The maximum recommended

continuous junction temperature is 150°C.

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