nRF52840 High Voltage Mode - External Circuitry Supply

[ZAC]

Hi, would you support with the following:

In the high voltage mode (defined as when the supply voltage is only connected to the VDDH pin and the VDD pin is not connected to any voltage supply), and when using the nRF52840 to supply external circuitry (from the VDD pin):

• Should the VDD pins be connected all together externally (also plus the recommended caps)?
• If not, which VDD pin should be used as a VEXT for supplying external circuitry?
• Also, I assume in that case that the GPIOs reference will follow the VDD level instead of the VDDH. Right?
• Is that correct in all cases any way? (GPIO reference voltage / external output supply voltage in high voltage mode). Background: I would need to get the right SPI/I2C levels for communication with another peripheral.
• Is it possible to set two different GPIO reference levels, for example one for an SPI, and one for a different I2C instance?

[Sigurd]

Hi,

• Yes, all the VDD pins should be connected externally. The caps should sit on each VDD pin. VDD is the global supply for the chip and it is decoupled on each corner to provide a clean, common power supply for the nRF52840 SoC.
• When the VDD pins are connected externally, you can choose yourself which VDD pin you want to use as VEXT.
• Yes, GPIO reference voltage will follow/use VDD.
• Is that correct in all cases any way? Yes.
• It is not possible to have different GPIO reference voltages.VDD operates between 1.8 V and 3.3 V depending on the selected voltage in UICR REGOUT0 register. In high voltage mode you can select between the following reference voltages: 1.8V, 2.1V, 2.4V, 2.7V, 3.0V and 3.3V. If you need e.g. 5V for one of the SPI or I2C devices, I recommend using a level shifter/translator