TRF3722: [TRF3722] Baseband Input VCM with AC-Coupling: Is External DC Bias Mandatory?

Part Number: TRF3722
Other Parts Discussed in Thread: DAC5688, , DAC38J84, TRF372017

Hello TI Team,

I am designing a transmitter chain using DAC5688 and TRF3722. Because of the DAC5688's output compliance (3.3V), I am using AC-coupling capacitors between the DAC outputs and the TRF3722 baseband inputs.

I have a question regarding the DC bias requirement for the TRF3722 inputs in this configuration.

Context & Confusion:

1. Datasheet: Table 17 states that "Typical 0.25V common mode is needed," and the input resistance is 5 kΩ. This implies that if left floating (AC-coupled), the input DC level might be undefined or drop to 0V.

2. EVM Schematic: However, the TRF3722 EVM schematic (Figure 135) does not show any external resistive network to establish this 0.25V bias.

Questions:

1. Does the TRF3722 have an internal self-biasing circuit that automatically sets the input VCM to ~0.25V when AC-coupled?

2. Or, is it mandatory to add external Thevenin termination resistors (e.g., to 3.3V and GND) after the AC caps to explicitly force the 0.25V bias?

3. Are there any reliability risks (damage or linearity degradation) if I connect the AC-coupling caps and leave the TRF3722 inputs floating without external bias resistors?

Thank you.