Can the BTM51x produce the Master I2S clock required by an external codec?

Answer

Unfortunately, BTM51x cannot provide such MCLK signal. Laird recommends you select an external codec IC which has the capability of creating the MCLK internally from the bit clock signal (SCK). Such capability is referred to as “PLL” (phase locked loop) or “FLL” (frequency locked loop) functionality of the codec device.