7.7 Power Supply Modes

The PIC32CX-BZ3 device supports a single power supply from 1.9-3.6V. The IO supply cannot be decoupled from the main supply. The same voltage must be applied to VDDx, PMU_VDDIO, VPMU_VDDC and AVDD with different levels of filtering. The internal voltage regulator has the following four different modes:

RUN mode – The PIC32CX-BZ3 device automatically gets into RUN mode upon power-up. This is the default state of the device.
- MLDO mode – Provide a soft start-up by using the MLDO, limiting the charging current. The MLDO also helps to extend the supply voltage range down to 1.9V below Buck BOR. This mode does not require external inductor.
- BUCK mode – The most efficient mode when the CPU and peripherals are running. In this mode, the DC-DC converter powers the SoC. This mode requires external LC-filtering and appropriate decoupling on-board before supplying power to other blocks.
  Note: BUCK mode is not supported in this silicon version due to an accuracy issue.
  BUCK mode has the following two operating modes:
  - PWM (Pulse Width Modulation) mode – Buck can deliver the highest output current with good efficiency. The internal switching clock in this mode is 1-2 MHz. In PWM mode, it is expected to reach an efficiency of 85%.
  - PSM (Pulse Skipping Mode) – This mode is recommended when the load current demand is low. The PSM mode is a type of frequency modulation scheme with an efficiency of up to 80%.
Low-power modes – The PIC32CX-BZ3 supports various low-power modes; Sleep, Deep-Sleep (DS) and Extreme Deep Sleep (XDS). See Power Management Unit (PMU) from Related Links for more details on how to transition from RUN mode to low-power modes.
IDLE mode – See Power Management Unit (PMU) from Related Links.

The on-the-fly software can do the selection between Switching (BUCK) mode and Linear (MLDO) mode. Be sure to design the power supply according to the type of mode in use.