9.2.5 REF1 and REF2 Blocks

The REF1 and REF2 blocks create midscale power-supply biasing points used internally to the AFE031. Each reference divides its respective power-supply voltage in half with a precision resistive voltage divider. REF1 provides a PA_V_S/2 voltage used for the PA, while REF2 provides an AV_DD/2 voltage used for the Tx PGA, Tx Filter, Rx PGA1, Rx Filter, and Rx PGA2. Each REF block has its output brought out to an external pin that can be used for filtering and noise reduction. Figure 35 and Figure 36 show the proper connections of the external noise-reducing capacitors. These capacitors are optional, but are recommended for best performance.

Figure 35. REF1 Functional Diagram

Figure 36. REF2 Functional Diagram