High-resolution analog-to-digital converters (24-bit Delta-Sigma ADCs like the ADS1256 or AD7175) require millivolt-clean reference rails. A few microvolts of ripple on your $V_{REF}$ or $AV_{DD}$ can easily degrade effective number of bits (ENOB) from 20 bits down to 14 bits.

Linear Regulators vs Switcher Post-Regulation

While buck converters offer >90% power efficiency, their high $di/dt$ switching harmonics can radiate across PCB planes. The best practice for mixed-signal systems is a hybrid SMPS + Low-Dropout (LDO) topology:

 +12V Input ──► [Buck Converter 3.6V] ──► [Ferrite π-Filter] ──► [Ultra-Low Noise LDO 3.3V] ──► ADC Analog Rail
                                                                 (TPS7A4700 / 4μVRMS Noise)

Ferrite Bead Damping & Anti-Resonance

Placing a ferrite bead directly in parallel with ceramic capacitors creates an LC tank circuit that can resonate at high frequencies, amplifying noise rather than attenuating it.

       Ferrite Bead (600Ω @ 100MHz)
 ───/\/\/\───────────────┬────────► To Analog Load
                         │
                    ┌────┴────┐
                   ===       [ R_damp 0.5Ω ]
                   === C_in   │
                    │        === C_bulk 10μF
                    │        ===
                   GND       GND

Component Comparison Table

Proper ground plane partitioning with a single unified solid ground plane underneath the converter section ensures minimal return path loops.