nrf52833 Power Reset

[lyrics]

Hello,

I'm working on a custom board with a nRF52833.

A small external battery is on the board, and when the power is off, 32.768khz of low power remains on the battery and only check the interrupt in idle mode.

However, when the power is turned off (power off), the battery has power left, but the low-power oscillator goes off immediately.

1. What is the cause of this problem? Is it checking internally the level of voltage and power reset?  

(I checked the datasheet that the power management is in the range of 1.7V to 5.5V, and the battery has power in the range.)

2. What should I do to solve this? How can I modify or check the 'power reset' configuration?

Best Regards, lyrics

[Einar Thorsrud]

Hi,

I am not able to fully understand the situation. Can you try to elaborate?

[lyrics]

Hi, 

My manufacturing board has a small back-up voltage, so it can be operated at low power even after the 5V power is turned off. I want to use that low power to operate the program in idle mode through the 32.768khz external oscillator even when the main board is powered off.

So, according to the designed circuitry, 32.768khz must continue to oscillate even if the current 5V power is turned off. However, at present, the main power is turned off and no longer oscillates (back-up voltage is still present).

I searched for reasons for this, look at this post and  this post.
So I thought it wouldn't work because it would reset the mcu internally if it fell below a certain current. (back-up voltage is in range 1.8V- 5.5V)

Is what I understand correct? Or what is the reason for the problem situation that I mentioned above?

I hope my question was delivered well.

 

BR, lyrics

[Einar Thorsrud]

Hi Lyrics,

lyrics said:

So, according to the designed circuitry, 32.768khz must continue to oscillate even if the current 5V power is turned off.

There is no backup voltage concept in the nRF devices, so this depends on how you have implemented your design. Can you share schematics and explain your HW design regarding this? I assume you are using the high voltage mode VVDH as you have such an high supply voltage? In high voltage mode, the minimum supply voltage (VVDH) is 2.5 V. 

lyrics said:

So, according to the designed circuitry, 32.768khz must continue to oscillate even if the current 5V power is turned off.

I see. I cannot say anything without knowing more about your HW design, though.

lyrics said:

the main power is turned off and no longer oscillates (back-up voltage is still present).

Is this the 32.768 kHz crystal oscillator of the nRF? If so you need to put the nRF in low power mode  yourself (system on, all peripherals expect LFCLK and RTC turned off). If it is a fully external clock then I cannot say what you need to do, other then somehow cut supply voltage to the nRF.

lyrics said:

Is what I understand correct? Or what is the reason for the problem situation that I mentioned above?

I hope my question was delivered well.

I think I understand the question, but as mentioned you need to explain details about your WH and share schematics.

Einar