nRF52840 DK not starting when nPM1300 VBAT = 2.7 V

[Sagar Patel]

Hello,

I have connected the nRF52840 DK to the nPM1300 EVK, with the DK powered from BUCK1 output of the nPM1300.

When I supply 3 V or higher to the VBAT pin of the nPM1300 (using an external supply), the nRF52840 DK powers up correctly and I can see the serial logs.

However, our requirement is for the firmware to operate down to 2.7 V. When I apply 2.7 V to VBAT, the DK does not start and no logs appear.

Could anyone please guide me on how to achieve operation at 2.7 V?
Is there any register configuration needed in the nPM1300 for this, or should I debug elsewhere?

Let me know if required more info.

Thank you for your support.

[Ressa]

Hi,

Thanks for contacting us. 
If you would like, we can review your schematic in case there might be some hardware issue. For that you just need to upload the schematic here. I make the ticket private so that the schematic will be visible to just me (and Nordic employees). 
* Just wondering what is the resistor values used for VSET pins on nPM1300 (VSET1 and VSET2)? If VBAT voltage gets closer to the voltage set by resistors, you might not get exact value you would expect, there will be some voltage drop.




Best regards,
Ressa

[Sagar Patel]

Sorry for late reply, Due to medical issue.

Can send me your mail id so that i can sent you the schematic for review ?

 

For VSET we have used 47K register, please check the screenshot attached.

[Ressa]

Hi, 

No problem. Based on the table I shared in previous message, to get 1.8 V on VOUT2 you should use resistor value of 4.7 K Ohm not 47 K ohm on VSET2.

Best regards,
Ressa