Most of the time, the voltage rails available in a system do not match the voltage specifications demanded by one or more of its circuits; these rails must be stepped up or down, depending on specific voltage requirements.

DC-DC converters are generally the preferred solution to stepping up or down a voltage rail when current consumption is not negligible. These devices offer high efficiency with minimum heat generation, but they have one primary disadvantage: they introduce a high-frequency component, and the associated harmonics, on top of the DC output signal.

If not filtered properly, this high-frequency component degrades analog circuitry performance, and reduces overall system accuracy and precision.

The TPS7H1210-SEP offers a wide-bandwidth, very-high power-supply rejection ratio (PSRR). This specification makes it ideal for post DC-DC converter filtering. TI recommends using a schematic like the one shown in Figure 8-2 for high performance. Also, verify that the TPS7H1210-SEP regulator PSRR is still high within the fundamental frequency (and its first harmonic, if possible) of the switching regulator.