Hi,
We don't have any demo that would work with the FDA903D Audio Amplifier, and both the SAI module and the amplifier support many formats.
I would recommend you to start with the sai_transfer_s32k148 SDK example, scope the bus and modify it as per the FDA903D datasheet.
But the I2S clock stays active between transfers.
To get better understanding of the SAI module, please refer to
AN12202 Using Synchronous Audio Interface (SAI) on S32K148.
https://www.nxp.com/docs/en/application-note/AN12202.pdf
BR, Daniel