nRF52840 Normal mode

[Nikosant03]

Hello,

We are designing a product based on the RAK4630 module that integrates nRF52840 SoC.

Since we are creating a low power consumption and battery operated product running on 1V8 our thought is to configure nRF52840 in Normal Mode and DC/DC REG1 enabled

From the RAK4630 module schematic it seems that an inductor (L10) is connected from VDD1 to DCCH and two additional inductors (L7,L8) are connected from DCC to DEC4 (same configuration as per your reference circuit). Based on the nRF52840 Regulator configuration examples, RAK4630 it seems to be configured as High Voltage mode, DC/DC for REG0 and REG1 enabled

My questions are:

1. Are we right that the minimum power consumpion is achieved with Normal Mode and DC/DC REG1 enabled configuration?
2. In case this is true, is there any work around with RAK4630 configuration? Or we should remove L10?
3. Regarding L7 & L8, if I understand correcly they are used to enable DC/DC regulator for REG1 stage right? Also the register settings DCDCEN performs the same task right? So since we want REG1 to be enabled, will keep L7 & L8 and will not interact with DCDCEN?

Thanks!!

 

[Hung Bui]

Hi Nikos, 

1. It depends on your power supply. If you have 3.0V supply then yes using Normal mode DC/DC bring you lowest power consumption. If you have 5V supply then you should use high voltage mode DCDC.

2. I don't think you have to remove L10. If you connect both VDDH and VDD to 3.0 V supply, REG0 will be skipped and having L10 shouldn't cause a problem. As far as I know we have the same setup on our nRF52840 DK where we support both Normal mode and High Voltage mode. 

3. Correct. If you want DCDC mode, you need to set DCDCEN=1 in the code. 

[Nikosant03]

Thank you for the prompt reply Hung!!

We will supply nRF52840 with 1.8V by the way.

Do you forseen any additional consumption if we leave this RC filter (L10 & C38) of RAK4630 in Normal Voltage mode, DC/DC REG1 enabled? 

[Hung Bui]

Hi Nikos, 

No, DCCH will be high impedance when you use normal mode (REG0 is disabled). L10 will not draw current. 
C38 is needed in any setup anyway.