Internally, DAC38RFxx comprises a digital subsystem, an analog subsystem, and a clock subsystem. Ideally, the power supply scheme should be partitioned according to these three relatively independent blocks to minimize interactions between them. Most importantly, sensitive analog and clock circuit power supply must be separated from digital switching noise to reduce direct coupling and mixing of switching spurs. Table 133 shows the power supply rails for DAC38RFxx grouped under their respective domains.
|Supply rail||Nominal voltage (V)||Domain|
An example power supply scheme suitable for most applications of DAC38RFxx is shown in Figure 155. It is recommended to use ferrite beads (FB) to isolate the individual rails from each other.
There are no power supply sequencing requirements for all the 1-V and 1.8-V power supplies. For the -1.8 V VEE18 rail, it is recommended that this supply is the last to be enabled. Enabling VEE18 (while other supply voltages are disabled) can cause a small negative voltage to be present at the other rails (that is, VDDA1 and VDDDIG1). This small negative voltage can interfere with the startup of some DC-DC converters or LDO's connected to the 1 V and 1.8 V input power rails.