nRF52840 power configuration

[vivekt]

Dear Sir/Madam


I am currently designing a IOT board using nRF5284 as the main controller IC

The board is battery powered and is charged using USB. Data can also be transferred using USB.

The nRF52840 is also used to transfer data using BLE. NFC is not used


Below are my queries


1.  The board works on 1.85V supply. In this condition I am not sure what supply configuration I should use. Can I use Config 3. as mentioned in page 529 of the datasheet.

Both VDD,VDDH =1.8V.   Can we connect 1.8V to VDDH in Mode 3.


2. Please provide reference Layout file for the Bluetooth Connection

Thanks & Regards

Vivek.T

[Jared]

Hi

1. The configuration that you should use depends entirely on the voltage range of your battery when it's in the depleted and full state. The entire battery range should be within either VDDH's operating range or VDD's. So if you battery is minimum 1.7 V when its depleted and maximum 3.6 when its full, you should use VDD. Which means that you should use configuration 3 normal mode. You should also make sure that the USB charging voltage is within the operating range of the VDD. This can be achieved by using a regulator between the charging voltage and VDD.
2. You can download the reference design here.

Cheers

Jared

[vivekt]

In the datasheet section 8 it is mentioned that  VDDH typical value should be between 2.5V to 3.5V. Is this for high Voltage mode only. When using config 3 in normal voltage mode  the VDDH can be 1.8V. Is my understanding correct. 

[Chris]

sorry for capturing that ticket (I can't create a new one since all dropdowns are empty).

But I think it's alright to post here as it has somewhat to do with VDDH:
We want to keep our design flexible, so basically I could be powered by VDD or VDDH. If I run our PCB with 3.3V at VDD, SWD works fine.
If I connect 5V to VDDH, I can see 1.8V at VDD but SWD (connected to DK) does not work. Is there a register to write to make it work or so? 

Circuitry is Configuration No.4

edit: could it be that SWDIO has to have the exact same voltage level? While testing something different I was powering the PCB with 3.5V and SWD from DK (GND connected) is not working. Just switching what has been 3.5V to 3.3V supply from DK and everything is working perfectly again

[Jared]

Hi

What is the voltage range of your battery source?

Cheers 

Jared 

[vivekt]

4.2V to 3.3V

[vivekt]

Also then what will be the IO voltage range(VOH/VIH) for all the GPIO pins.

[Jared]

Hi

I'm not sure I understand your setup correctly. You mention that your source is 1.8 V, why is your battery range 4.2 V to 3.3 V than? 

As stated in the product specification: "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 high-voltage mode does therefore use more energy as the system use a two-stage regulator setup.

Jared