The internal VREG is supplied by VDDIO and generates the 1.2 V required to power the VDD pins. Enable this functionality by pulling the VREGENZ pin low to VSS. The smaller pin-count packages may not include the VREGENZ pin; therefore, the internal VREG is always enabled and, as such, is the required supply source for the VDD pins. Review the description of VREGENZ in to determine package configuration. Although the internal VREG eliminates the need to use an external power supply for VDD, decoupling capacitors are required on each VDD pin for VREG stability. There are two recommended capacitor configurations (described in the list that follows) for the VDD rail when using the internal VREG. The signal description for VDD can be found in Table 4-4.