The device requires two different power-supply voltages. 1.9 V DC is required for the VA19 power bus and 1.1 V DC is required for the VA11 and VD11 power buses. VLVDS can be set to any voltage between 1.9 V and 1.1 V. The LVDS output driver common-mode voltage tracks the VLVDS supply voltage. In general, a 1.9-V supply voltage for VLVDS can be used for standard LVDS receivers.

The power-supply voltages must be low noise and provide the needed current to achieve rated device performance.

There are two recommended power-supply architectures:

1. Step down using high-efficiency switching converters, followed by a second stage of regulation to provide switching noise reduction and improved voltage accuracy.
2. Directly step down the final ADC supply voltage using high-efficiency switching converters. This approach provides the best efficiency, but care must be taken to ensure switching noise is minimized to prevent degraded ADC performance.

TI WEBENCH? Power Designer can be used to select and design the individual power-supply elements needed: see the WEBENCH? Power Designer

Recommended switching regulators for the first stage include the TPS62085, TPS82130, TPS62130A, and similar devices.

Recommended low dropout (LDO) linear regulators include the TPS7A7200, TPS74401, and similar devices.

For the switcher only approach, the ripple filter must be designed with a notch frequency that aligns with the switching ripple frequency of the DC/DC converter. Make a note of the switching frequency reported from WEBENCH? and design the EMI filter and capacitor combination to have the notch frequency centered as needed. Figure 8-12 and Figure 8-13 illustrate the two approaches. Do not share VLVDS with the analog supply voltages in order to prevent digital switching noise from coupling into the analog signal chain. If VLVDS must be shared with either VA11 or VA19, apply careful power supply filtering to limit digital noise at the analog supply pins.

FB = ferrite bead filter.

Figure 8-12 LDO Linear Regulator Approach Example

Ripple filter notch frequency to match the fs of the buck converter.

FB = ferrite bead filter.

Figure 8-13 Switcher-Only Approach Example