I've been asked by a client to supply exact copies of some low pass filters that he had manufactured in 1998. The boards use LMF60CIN 6th order switched butterworth low-pass filters which are now dis- continued. I've explained this to him but he is adamant that we supply him a replica of what he has so that it is retro-compatible.
Is there a direct replacement for this chip available or will I have to check the obsolete part suppliers?