What is the behavior and failure mode of the LT1761 when operated close to and above its junction temperature?
As the max junction temperature is approached and exceeded, what is the effect on the output voltage.
Is it possible for the part to become unstable at max temperature - output filter cap is 10 uF ceramic.
LT1761 has thermal limiting protection. The output current will be reduced when the junction temperature is above the threshold temperature of the protection, which is about 155C. The output voltage may go down at the same time depending the load characteristic. After the current is reduced, the junction temperature will go down. The part will get out from thermal limiting protection, and the output is regulated again. So you may see the oscillation at the output. The part will not be damaged, but it is only a protection and the part is not supposed to run over 125C for long.