All of these devices will support DDR1, DDR2, and DDR3. DDR2, for example has a VDDQ of 1.8V and a VTT of 0.9V. The 0.9V must track the variations of 1.8V within 3% and be able to source and sink current. One interesting note: There are actually 2 pass elements in the LDOs. One pass MOSFET sources current, and another sinks current. The synchronous buck controllers and converters shown here inherently source and sink current.