Custom PCB & is it okay to run SPI at 1.8V?

[ryerye120]

Hi,

I have two questions:

1) I'm making a custom board for a hobby project! Are there any limitations to running a SPI driver with a voltage high of 1.8V? It seems that if I short the chips VDD and VDDH to 3.3V and set the REGOUT register to 1.8V, I should be able to run spi at 1.8V. 

2) Do you guys still do PCB design reviews? If so, that would be AWESOME! How can I submit a PCB schematic/layout for review?

Thank you for your time! Your guys' support forum has always been the best!

- Ryan

[ketiljo]

1. Just connect VDD to VDDH and supply both with 1.8 V. See https://infocenter.nordicsemi.com/topic/ps_nrf52840/power.html#unique_1386123489, figure 1. 

 REGOUT0 is only in use in the high voltage mode, where you have a higher voltage on the VDDH pin only. 

2. Open an new, private case and ask for a review. Attach the schematic as pdf and the layout as gerber files. 

[ryerye120]

I can just run the entire chip off of 1.8V? Will this affect Bluetooth at all?

I'll open a private case when I'm ready!

Thank you so much!

[ketiljo]

Sure, the chip can operate from 1.7 to 3.6 V in normal mode: https://infocenter.nordicsemi.com/topic/ps_nrf52840/power.html#unique_1730776566

There are internal regulators for the different power domains. The radio operates at a lower voltage so the performance remains the same within the operating voltage range. 

[ryerye120]

Ahh okay! So I'm trying to see which circuit config I can use on my PCB. Since I'm operating everything on 1.8 V I probably don't need anything fancy so would circuit config 3 work for my custom design? Where VDD would just be 1.8V. Since I don't need to step any voltages up/down I don't think I really need the DCDCEN0/1.

Taken from: infocenter.nordicsemi.com/index.jsp