Q
What is the maximum junction temperature of AD698 or the maximum permissible
power dissipation? This is not specified in the datasheet or any other related
documentation.
A
The AD698 is around 30 years old and I don’t believe the max junction
temperature was determined during product characterization and release. Also
the max power dissipation of this device really depends on the power dissipated
by the transducer driver circuit and the load at the signal output.
The worst case junction temperature would be 125C since we have a model of the
AD698 with a guaranteed ambient temperature of 125C. The die inside both
models is the same, it’s just packaging that influences each different
temperature range.
The best case is 150C since this is the storage temperature rating. The die
storage temp ensures that no permanent damage will result if the die
experiences sustained temps up to 150C. While we'd expect the device to more or
less function beyond the max ambient temperature up to the max storage
temperature, ADI would expect non-destructive (recoverable) performance
degradation due to heat when exceeding an ambient temperature. Performance of
this device in customer applications operating outside of data sheet operating
conditions can’t be guaranteed by ADI.