Instability in current consumption when SAADC off

RE: Instability in current consumption when SAADC off

Karl Ylvisaker — Thu, 15 Feb 2024 15:34:43 GMT

Hello Simon,

[quote user="SimonD"]Sorry for the verified answer, I made a mistake while I was replying.[/quote]

No need to apologize - I just felt bad that you had gone without a reply from us for so long.

Thank you for elaborating on the rest of the application!

[quote user="SimonD"]

When the SAADC is off, we stil have an inertial center (IMU) running. Every 0,2ms, we check the gyroscope to know if we need to wake up the analog part of our device.

In the same time, we have calculation made in the nRF52 microcontroleur. But those calculation are the same as in the full working mode (with the analog part running).

I had delay to answer because we have developed a new prototype card the will enable us to mesure component's consumption separately, so that we will be able to be sure which component is at the origin of theses instabilities.

[/quote]

Still, even with the CPU of the nRF52 running continuously you would not be seeing consumption up towards 20 mA, and so there must be something else at play here.
I'm glad to hear that you've made additional hardware that will allow you to isolate the root of these oscillations.
I look forward to hearing about the results of the tests, if you would update me!

If you would like, we could also perform a schematic review of the nRF related circuitry for you. If you would like us to do so, please open a separate private ticket for this and share your schematics and gerber files so that our hardware engineers could take a look.

Best regards,
Karl

RE: Instability in current consumption when SAADC off

SimonD — Thu, 15 Feb 2024 08:52:23 GMT

Hi Karl,

Sorry for the verified answer, I made a mistake while I was replying.

When the SAADC is off, we stil have an inertial center (IMU) running. Every 0,2ms, we check the gyroscope to know if we need to wake up the analog part of our device.

In the same time, we have calculation made in the nRF52 microcontroleur. But those calculation are the same as in the full working mode (with the analog part running).

Best regards,

Simon

RE: Instability in current consumption when SAADC off

Karl Ylvisaker — Wed, 24 Jan 2024 16:16:35 GMT

Hello again, Simon

Thank you for your extreme patience with this. I notice now the additional question you had - the ticket had gotten the 'verified answer' status internally due to the original comment being marked as the correct answer, and so it fell off my radar for a while, unfortunately.

[quote user="SimonD"]Accidentally (to test other things) I have deactivated that power supply to use the classical LDO one and all oscillation have disappeared. Is there any particular way to uninit the saadc when using the DC/DC power supply ? [/quote]

I do not think that the power measurements you have shown could possibly stem from the SAADC alone - especially so with the DCDC part of the design, as this will reduce overall power consumption for very power intensive scenarios.

Could you elaborate on what else is happening in your application and hardware at the time of these measurements?

Best regards,
Karl

RE: Instability in current consumption when SAADC off

SimonD — Fri, 05 Jan 2024 19:26:59 GMT

Hi,

For our product, we are using the DC/DC power supply of the nRF in order to save energy. To activate that we use the following command :

sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);

Accidentally (to test other things) I have deactivated that power supply to use the classical LDO one and all oscillation have disappeared. Is there any particular way to uninit the saadc when using the DC/DC power supply ?

Thank you for your answer !

Best regards,

Simon

RE: Instability in current consumption when SAADC off

SimonD — Tue, 02 Jan 2024 11:38:44 GMT

Hi Karl,

Thank you for your answer. Wish you a happy new year !

We didn't see the Errata but I tested it and it doesn't change anything in our case. It's like I didn't change anything.

When we uninit the saadc, there are operations made on our pcb. We have an IMU working and the application will check every 20ms if the device is put into rotation. If it is the case, we active the saadc. If it's not, we continue waiting.

Also, during that period, we continue to communicate wireless with others devices.

But those operations are done also when the saadc is working and no apparent problem occurs during that period.

As you can see in the picture, at the red row we uninit the saadc, and oscillations start.

Would you have other tests to proprose ?

Thank you,

Best regards,

Simon

RE: Instability in current consumption when SAADC off

Karl Ylvisaker — Mon, 18 Dec 2023 10:49:48 GMT

Hello Simon,

Thank you for your patience with this.
Please note the Errata 241 for the nRF52832, which could lead to an increase in power consumption following the uninit of the SAADC. Please make sure to apply the workaround from this errata to see if this is the cause of the unexpected current consumption.

If it is not, could you elaborate on what else is on-going in the application at the time where you have measured the current consumption shown in the power trace?

Best regards,
Karl