I’m really sorry for the delay in response.
VCOM is generated by the codec as a reference voltage. It’s VCC / 2, so in this case 2.5V.
This post explains it well: voltage reference - Why is the Vref of the DAC used in the op-amp amplifier stage? - Electrical Engineering Stack Exchange.
I’ve also attached a reference circuit from the PCM3060 datasheet that uses it.
