Heating issue of AD734

I am using AD734 as a RMS-to-DC Converter(Page no 16 of datasheet).
My circuit is same as that of given in datasheet. But IC is getting heated to 72 celsius (or 161 F) when I am giving 1 to 100 Hz sinewave sweep (T=20 sec) periodically at input.
Is it expected to get heatup?
Should I go for dedicated IC AD636 for RMS calculation?