DS90UB948-Q1: ds90ub948 thermal protection

Terry,

As you mentioned, the maximum allowed operating air temp. and junction temp. of UB948 is 105C and 150C. To understand these two specs., please refer to Ti's app. note on thermal metrics (http://www.ti.com/lit/an/spra953c/spra953c.pdf

Ambient Air Temperature— Multiple sources list different locations for determining the ambient air
temperature. NEBS specifies the air temperature coming into the system box as ambient. AEC
specifies the air temperature under the device as the ambient. JEDEC specifies the air stream
temperature in advance of the PCB. Sometimes the ambient air temperature is taken above the
device as an understanding of ambient. Each of these measurement locations yields a different
temperature for the ambient air temperature. It is important to understand, in any case, that the
critical factor affecting device reliability and functionality is the junction temperature, not the ambient
temperature. Because the junction temperature and ambient temperature are interrelated,
clarification of the ambient temperature assumption is crucial before any system level analysis is
undertaken.
Junction Temperature— The hottest temperature of the silicon chip inside the package.

please refer to Ti's app. note on thermal metrics (www.ti.com/.../spra953c.pdf) on thermal parameter definitions.
for this case, if the chamber temp. is increased to 90C, and the case temp. of UB948 is NOT too high, it should have no any problem. so if the UB948 is damaged, you should check the UB948 thermal design? whether the case temp. of UB948 is too high (due to nearby thermal source? shielding?...) thanks.

regards,
Steven