The MAX98400B is designed to be used for Stereo applications, the MAX98400A is the suggested option for Mono applications. However, the MAX98400B can be implemented to receive mono signals. In this configuration, only one Channel used. This setup only implements one channel as input and one channel for output. The power consumption and noise figure need to be tested but this is viable option for using this IC with a mono signal.
Two Channel mono input, two speaker outputs: