TLV320DAC3100: analog inputs connected to a host micro DAC

Hi, Lenio,

Please take a look at my responses below and let me know if you have additional questions or comments.

1. Should the signal be centered in the middle of the 3.3V rail, or 1.15V?

The analog inputs should be centered at 1.65V when using a 3.3V rail. In that way, you can mix the analog input with the DAC signal without issues.

2. Why is the analog audio full-scale input voltage limited at 0.7VRMS? (section 4.3 of the DS).

The audio full-scale level is set in order to ensure a good output level without clipping, even if the power supply level is the minimum. For example, let's say that the SPKVDD and AVDD level is set at 2.7V (min recommended value). The middle point will be at 1.35V. Having a 0.7Vrms level would place the min level at 0.35V and the max level at 2.35V.

The digital volume and the output volume can be used to increase the signal level if required.

3. What are the best practices for connecting the DAC of the microcontroller to the analog inputs AN1/2? Should a filter be used? Any impedance concerns?

What we recommend when routing the AN1/2 signals is that they shouldn't be crossed with the digital portion. Otherwise, there's risk to have high frequency noise content at the output. In addition, it is a good practice to remove the out-of-band noise from a DAC before connecting the lines to the AN1/2. You can find more information in this app note:

https://www.ti.com/lit/an/slaa313a/slaa313a.pdf

Best regards,
Luis Fernando Rodríguez S.