3.3V power supplies

Yes, it is possible to power both 3.3 V supply groups of the ADF4382 from a single LDO, but with some important caveats.

The two 3.3 V groups are separated to keep sensitive blocks (VCO, output dividers, RF outputs) isolated from potentially noisy digital/phase-detector related rails (e.g., V3_PFD, NDIV). This partitioning is a precaution to prevent switching noise from coupling into the VCO and degrading phase noise. It is not strictly proven that separate regulators are mandatory, but it is the recommended configuration for best performance. 

If you use a single LDO, you should at minimum:

• Use separate filtering/inductor or ferrite bead isolation for the “sensitive” group (VCO, OUTDIV, RFOUTx) versus the “digital/PFD” group to limit noise coupling.

• Ensure the bead/filters do not introduce more than about 0.3 V drop or violation of rail tracking, since supply differences between rails should stay within about ±0.3 V of each other.

Phase-noise degradation is possible if noise from the PFD/digital section couples into the VCO supply when everything is tied directly together. As a result we often  recommend separate LDOs (or at least well-isolated subrails) for analog, digital, and VCO supplies to minimize this risk. Using one high‑quality LDO plus proper LC/ferrite isolation is often an acceptable compromise, but strictly best-in-class phase noise is more likely with fully separate regulators. 

Yes, it is possible to power both 3.3 V supply groups of the ADF4382 from a single LDO, but with some important caveats.

The two 3.3 V groups are separated to keep sensitive blocks (VCO, output dividers, RF outputs) isolated from potentially noisy digital/phase-detector related rails (e.g., V3_PFD, NDIV). This partitioning is a precaution to prevent switching noise from coupling into the VCO and degrading phase noise. It is not strictly proven that separate regulators are mandatory, but it is the recommended configuration for best performance. 

If you use a single LDO, you should at minimum:

• Use separate filtering/inductor or ferrite bead isolation for the “sensitive” group (VCO, OUTDIV, RFOUTx) versus the “digital/PFD” group to limit noise coupling.

• Ensure the bead/filters do not introduce more than about 0.3 V drop or violation of rail tracking, since supply differences between rails should stay within about ±0.3 V of each other.

Phase-noise degradation is possible if noise from the PFD/digital section couples into the VCO supply when everything is tied directly together. As a result we often  recommend separate LDOs (or at least well-isolated subrails) for analog, digital, and VCO supplies to minimize this risk. Using one high‑quality LDO plus proper LC/ferrite isolation is often an acceptable compromise, but strictly best-in-class phase noise is more likely with fully separate regulators.