The ADC32RF5x requires four different power-supplies. The AVDD18, AVDD12 and CLKVDD rail provides power for the internal analog and clocking circuits of the ADC while the DVDD rail powers the digital logic (including averaging and decimation filter) and the JESD204B digital interface.

Power sequencing is required as shown in Section 8.3. The AVDD18, AVDD12 and especially the CLKVDD power supply must be low noise to achieve data sheet performance. For applications operating near DC, the 1/f noise contribution of the power supply needs to be considered as well.

Power supply decoupling capacitors (0.1 µF) as close to the pins as possible on the top layer are recommended.

Figure 8-5 Power supply rejection ratio (PSRR) vs frequency

The recommended power supply architecture for a low noise design is to first use a high-efficiency step down switching regular, followed by a second stage of regulation using a low noise LDO for each power rail as shown in Figure 8-6. This provides additional switching noise reduction and improved voltage accuracy.

TI WEBENCH® Power Designer can be used to select and design the individual power-supply elements. Recommended switching regulators for the first stage include the LMS3635, and similar devices. Recommended low dropout (LDO) linear regulators include the TPS7A8400, and similar devices.

Figure 8-6 Power supply design example

AVDD12 or CLKVDD should not be shared with the DVDD to prevent digital switching noise from coupling into the analog domain.