Question of SN74CB3T3125 operation when Ta exceeds the recommended range

Takahiro-san,

Question 1.

There is the information of Operating free-air temperature(Ta) in datasheet p.4.

But we want to check the case tenperature(Tc).

Do you know the recommended range of Tc?

Why does the case temperature matter in your design?

This application not explains the thermal metrics in more detail.

Question 2.

Do you know the influence for operation when the Ta exceeds the recommended range?

For example, Ta of recommended  is 85℃(max), but if Ta of customer's condition is 87~88℃.

Note 1 of the abs max table states the influence for operation outside the recommended range.

Question 3.

Please tell us the recommended condition and place of measurement to check the Ta(Operating free-air temperature).

This will depend on your PCB design and enclosure but you want to measure near the device.  The app note above provides more detail.

Thank you,

Adam