AM and FM reception with the same antenna
The usual technique is to use a pair of filters to connect the common antenna to the two chip inputs. Basically, a low-pass filter for the AM input and a high-pass filter for the FM input, although more-specific bandpass filters for each band would do a better job of rejecting out-of-band signals. Each filter has a high impedance in the other filter's active range, so they don't affect each other significantly.