NRF52820-QDAA-R datasheet(50/437 Pages) NORDIC

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Power and clock management

• Separate USB supply

5.3.1 Main supply

The main supply voltage is connected to the VDD/VDDH pins. The system will enter one of two supply

voltage modes, Normal or High Voltage mode, depending on how the supply voltage is connected to these

pins.

The system enters Normal Voltage mode when the supply voltage is connected to both the VDD and VDDH

pins (pin VDD shorted to pin VDDH). For the supply voltage range to connect to both VDD and VDDH pins,

see parameter VDD.

The system enters High Voltage mode when the supply voltage is only connected to the VDDH pin and the

VDD pin is not connected to any voltage supply. For the supply voltage range to connect to the VDDH pin,

see parameter VDDH.

The register MAINREGSTATUS on page 66 can be used to read the current supply voltage mode.

5.3.1.1 Main voltage regulators

The system contains two main supply regulator stages, REG0 and REG1.

REG1 regulator stage has the regulator type options of Low-droput regulator (LDO) and Buck regulator

(DC/DC). REG0 regulator stage has only the option of Low-dropout regulator (LDO).

In Normal Voltage mode, only the REG1 regulator stage is used, and the REG0 stage is automatically

disabled. In High Voltage mode, both regulator stages (REG0 and REG1) are used. The output voltage of

REG0 can be configured in register REGOUT0 on page 36. This output voltage is connected to VDD and is

the input voltage to REG1.

Note: In High Voltage mode, the configured output voltage for REG0 (REGOUT0 on page 36) must

not be greater than REG0 input voltage minus the voltage drop in REG0 (VDDH - VREG0,DROP).

By default, the LDO regulators are enabled and the DC/DC regulator of REG1 stage is disabled. Register

DCDCEN on page 66 is used to enable the DC/DC regulator for REG1 stage.

When the REG1 DC/DC converter is enabled, the LDO for the REG1 stage will be disabled. External LC

filters must be connected for the DC/DC regulator if it is being used. The advantage of using the DC/DC

regulator is that the overall power consumption is normally reduced as the efficiency of such a regulator

is higher than that of a LDO. The efficiency gained by using the DC/DC regulator is best seen when the

regulator voltage drop (difference between input and output voltage) is high. The efficiency of internal

regulators vary with the supply voltage and the current drawn from the regulators.

Note: Do not enable the DC/DC regulator without an external LC filter being connected as this will

inhibit device operation, including debug access, until an LC filter is connected.

5.3.1.2 GPIO levels

The GPIO high reference voltage is equal to the level on the VDD pin.

In Normal Voltage mode, the GPIO high level equals the voltage supplied to the VDD pin. In High Voltage

mode, it equals the level specified in register REGOUT0 on page 36.

5.3.1.3 Regulator configuration examples

The voltage regulators can be configured in several ways, depending on the selected supply voltage mode

(Normal/High) and the regulator type option for REG1 (LDO or DC/DC).

Four configuration examples are illustrated in the following figures.

4463_156 v1.0

NRF52820-QDAA-R Datasheet(PDF) 50 Page - Nordic Semiconductor

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