Difference Between UC3524AN and SG3524N

Yes. One was designed and intended to be a second-source part of the other, but I double checked by looking at old 1977, 1990 and 1993 datasheets. There are actually a large number of suppliers of this jellybean PWM controller. I see it offered for as little as 62 cents (qty 100) at the major suppliers; this low price is one reason for its continuing popularity. Another is the huge mass of suppliers and users, which gives an engineer comfort as he's choosing the part for a new instrument, that it'll continue to be available for decades to come.

thanks for your answer