Regarding nRF52840

[Nikunj_17]

Hello

    I am developing a board using nRF52840. I have one doubt i can used internal regulator when i power on vddh and how to select voltage level My requirement is 3.3V.

   2) How to design antenna for nRF52840. 

[dejans]

Hi,

Regulator REG0 is enabled in normal voltage mode. In high voltage mode both regulator stages (REG0 and REG1) are enabled. Each of the stages has 2 potential regulator types - LDO and DC/DC. The output voltage from REG0 can be configured via REGOUT0 register and this output voltage is connected to VDD. You can read more in main voltage regulators. If you want to have 3.3 V on VDD in high voltage mode, you would need to have at least 3.6 V as the REG0 input (VDDH value). This is shown in the electrical specification.

There are several different types of antennas which you could use for the design. There is a chip antenna which you can find on 21540dk. You can take a look at 21540 hardware files. 21540dk use antenna with manufacturer part number 2450AT18B100. You can choose some other 2.4 GHz antenna as well. You could contact antenna manufacturer for potential assistance.
Another option is to use pcb antenna which is used on most DKs. One type is 1/4 wavelength printed monopole antenna. This kind of antenna can be found for example in nrf52840dk (hardware files) or nRF5340dk (hardware files). More information about this type of antenna is available in this whitepaper. Another type is meander monopole antenna which can be found on nRF52840dongle (nRF52840dongle hardware files).
Last option is to use external antenna working on 2.4 GHz.

Best regards,
Dejan