Current profile in sleep mode

[fedi makni]

Hello,

We are using nrf52832 in our development, we recently got the otii arc to measure the power consumption of our device.

During sleep mode we notice a huge spikes of 56uA as you can notice in the attached picture. After looking to some information in the forum i found that it could be related to the refresh mode of the regulator, i understand that it's something related to the chip, but i have some questions:

• How can we reduce these spikes?
• What will happen if the refresh mode doesn't exist in the chip?
• Are there other chips which the refresh mode doesn't exist?
• Any other technique to reduce the current consumption during sleep mode?
• How can we achieve the ultra low power mentioned in the datasheet between 1.2uA to 1.9uA

To note we are putting the IC to sleep mode and waiting for an interrupt from GPIO we are also using I2C

Thank you very much for your support.

[Einar Thorsrud]

Hi,

How can we reduce these spikes?

Refresh mode is always enabled when in low power sleep.

What will happen if the refresh mode doesn't exist in the chip?

All nRF52 series devices have refresh mode.

Are there other chips which the refresh mode doesn't exist?

nRF51 series.

Any other technique to reduce the current consumption during sleep mode?

The refresh mode is one of the techniques used to ensure lowest possible average sleep current (which is normally what matters in batter powered devices). With this method, the regulator is on a short time, and off most of the time when current consumption is low. (This is because there is some loss in the regulator itself, and not using it more than required minimizes average current consumption).

How can we achieve the ultra low power mentioned in the datasheet between 1.2uA to 1.9uA

This is something you can achieve when using system on low power mode with no resources active. If you have a LFCLK and RTC running (which is typically used in most real products as they need to keep track of time and wake up after a certain amount of time), you typically see a sleep current of about 2 uA. Not that all these numbers refers to average current consumption, and seen as there is refresh mode the peak current consumption will be much higher.

To note we are putting the IC to sleep mode and waiting for an interrupt from GPIO we are also using I2C

Depending on how you have configured the wake on GPIO the current consumption is different. In this case, you must use SENSE and not GPIOTE PORT event in order to minimize the current consumption. You could even use system off in this case, but then wakeup would be after a reset so this may not reduce the actual average power consumption, depending on your application (as everything must be initialized again).