8 Optional 1.2-V Internal DCDC

The F28004x device has three options for supplying the 1.2 V VDD voltage:

• An external supply (not available for 56-pin RSH package configurations)
• Internal 1.2-V LDO Voltage Regulator (VREG)
• Internal 1.2-V Switching Regulator (DC-DC)

The internal DC-DC regulator offers increased efficiency over the LDO for converting 3.3 V to 1.2 V. For detailed information on the DC-DC, see the TMS320F28004x Piccolo™ Microcontrollers Data Manual. Figure 4 shows the schematic implementation. If the internal DC-DC regulator is not used, VFBSW and VSW pin can be configured as GPIO22 and GPIO23, respectively. Note that VSW pin has an internal capacitance of approximately 100 pF, so it is suggested to use this pin only for applications that do not require a fast switching response.

Figure 4. DC-DC Circuit Schematic