Datasheet

2.9.7.2. External Core Supply
The digital core (DVDD) can be powered directly from an external 1.1V supply, rather than from the on-chip regulator, as
shown in Figure 17. This approach may make sense if a suitable external regulator is available elsewhere in the system,
or for low power applications where an efficient switched-mode regulator could be used instead of the less efficient
linear on-chip voltage regulator.
If an external core supply is used, the output of on-chip voltage regulator (VREG_VOUT) should be left unconnected.
However, power must still be provided to the regulator input (VREG_VIN) to supply the chip’s power-on reset and brown-
out detection blocks. The on-chip voltage regulator will power-on as soon as VREG_VIN is available, but can be
shutdown under software control once the chip is out of reset. See Section 2.10, “Core Supply Regulator” for details.
Figure 17. using an
external core supply
2.9.7.3. 1.8V Digital IO with Functional USB and ADC
Applications with digital IO signal levels less than 3.3V will require a separate 3.3V supply for the USB PHY and ADC, as
the USB PHY does not meet specification at voltages below 3.135V and ADC performance is compromised at voltages
below 2.97V. Figure 18 shows an example application with the digital IO (IOVDD) powered at 1.8V and a separate 3.3V
supply for the USB PHY (USB_VDD) and ADC (ADC_AVDD). In this example, the voltage regulator input (VREG_VIN) is
connected to the 1.8V supply, though it could equally have been connected to the 3.3V supply. Connecting it to the 1.8V
supply will reduce overall power consumption if the 1.8V supply is generated by an efficient switched-mode regulator.
RP2040 Datasheet
2.9. Power Supplies 181