What is the rated current spec and peak current value for AD590?
The AD590 “rated current spec” is just the maximum current the part will draw and is 1uA times the maximum operating temperature in K. Peak current value would apply to a dynamic circuit that would draw high current for short periods of time that was significantly above the average current. That just does not apply to the AD590. Or to put it another way, the two specs would be the same. Because the AD590 maximum operating temperature is +150C, 450uA will cover it.