low power (system on mode) in ble_uart_app

RE: low power (system on mode) in ble_uart_app

Jørgen Holmefjord — Thu, 21 Nov 2019 09:35:34 GMT

The recommended current measurement point is P22/P23. All current to the nRF-chip (VDD_nRF/VDD_HV power domains) will flow through here, excluding all other components on the board that may draw current from the power supply.

RE: low power (system on mode) in ble_uart_app

eleven-x_devteam — Tue, 29 Oct 2019 13:45:01 GMT

Hi,

[quote userid="14926" url="~/f/nordic-q-a/52921/low-power-system-on-mode-in-ble_uart_app/216605"]If you want to measure the current by the nRF only, you should set SW6 to "nRF Only" in addition to SW10 in ON state.[/quote]

Then, with this condition could P21 be more accurate than other ways like measuring at VDDH or Li-po?

RE: low power (system on mode) in ble_uart_app

eleven-x_devteam — Thu, 24 Oct 2019 21:18:52 GMT

Thank you for your help.

So After setting nRF Only, it went down to similar level to the Li-po case.

SW9 VDD, connecting external supply P21 to 3.5v, SW10 ON, SW6 nrf Only measured at P21: 1.3 uA

RE: low power (system on mode) in ble_uart_app

Jørgen Holmefjord — Thu, 24 Oct 2019 12:06:10 GMT

P21 is powering the entire board, including LEDs, debug chip, etc. If you want to measure the current by the nRF only, you should set SW6 to "nRF Only" in addition to SW10 in ON state.

RE: low power (system on mode) in ble_uart_app

eleven-x_devteam — Tue, 22 Oct 2019 21:13:49 GMT

WIth a new device, I measured pwr_mgmt app current consumption. The result is different from the old one.

[system off mode]

SW9 VDD, measured at VDDH P23: less than 1 uA

SW9 USB , measured at VDDH P23: less than 1 uA

SW9 Li-po , measured at P27 Li-po: 1.2 uA

SW VDD, connecting external supply P21 to 3.5v SW10 ON, measured at P21: 44 uA

About P21, do I need to do something before measuring?

Thank you.

RE: low power (system on mode) in ble_uart_app

eleven-x_devteam — Mon, 21 Oct 2019 21:44:06 GMT

Hi,

Thank you for your reply.

Yes, I am measuring nrf52840 DK.

[quote userid="14926" url="~/f/nordic-q-a/52921/low-power-system-on-mode-in-ble_uart_app/215933"]Can you try powering from an external supply on the LiPo header?[/quote]

-> Do you mean P21 or P27? If P27, it's 0.7uA as I said before. If P21, my DK just died so I'll check once I get a new one but I remember DK hasn't boot with P21. For measuring at P21, it there any preparation for it?

RE: low power (system on mode) in ble_uart_app

Jørgen Holmefjord — Mon, 21 Oct 2019 12:51:36 GMT

To be clear, you are measuring the current on the nRF52840 DK and not on a custom board, right?

There is a lot of noise on the DK from USB and 5V boost regulator, which makes it hard to measure current in µA range. Can you try powering from an external supply on the LiPo header?

RE: low power (system on mode) in ble_uart_app

eleven-x_devteam — Wed, 16 Oct 2019 15:18:29 GMT

Do you have any update for this?

RE: low power (system on mode) in ble_uart_app

eleven-x_devteam — Wed, 09 Oct 2019 20:47:14 GMT

Hi,

Thank you for your support.

I was using USB for power source (SW9) so VDD is 1.8V and VDDH 5.0V.

For measuring at VDDH of DK, I cut SB41 and connect P23 to 0.1 uA resolution multimeter(Agilent 34401A).

Also I've checked VDDH current with Li-Po for power source (SW9) 3.0v and it was same (6uA for system off).

As per your question, when I check VDDH current with VDD 3.0v (SW9), the result was less than 300nA.

Also I tested Li-Po P27 current with Li-Po for power source (SW9) 3.0v and it was 0.7uA

I guess it should be done directly at battery power source like P27 rather than VDDH or VDD, does it make sense? Or maybe other reasons to need to measure VDD or VDDH, then please let me know.

And another question is when I use Li-Po as power source, if I disconnect USB cable, it makes around 70mA current at P27. (I wanted to make sure to cut everything can affect current consumption)

Can you tell me why that happen?

Thank you.

RE: low power (system on mode) in ble_uart_app

Jørgen Holmefjord — Tue, 08 Oct 2019 13:52:26 GMT

How did you measure the current consumption?

I did a quick test with the ble_app_uart example, where the only modifications was to enable DCDC (should not affect system OFF current) and disable NRF_LOG.

When running this on a nRF52840 DK v1.1.0, I get about 350-400 nA current consumption with default supply voltage (3.0 V) using the PPK:

I have not yet tested with 5V supply, but I do not expect it to be higher. Have you measured with 3 V supply?

RE: low power (system on mode) in ble_uart_app

eleven-x_devteam — Mon, 07 Oct 2019 15:27:38 GMT

Hi Jørgen Holmefjord,

Thank you for your support.

About the chip info, my DK has PCA10056 1.1.0 and NRF52840 QIAAD0.

And even if I add the erratta 89 workaround codes, it can reduce the current just by under uA and still around 6.uA for system off mode and 9uA for system on mode.

It seems there is something making the current by extra 6uA consistently.

FYI, I am using ble_app_uart in SDK 15.3.0 59ac345.

Basically, I didn't change anything but the codes in my question above.

Do you have something else to recommend to do like disabling clock...?

Thank you.

RE: low power (system on mode) in ble_uart_app

Jørgen Holmefjord — Mon, 07 Oct 2019 12:23:23 GMT

Hi,

6 uA in System OFF mode sounds a bit high. According to the PS, typical current consumption in System OFF with wake on reset running from 5 V is 0.95 uA (I_{OFF_RAMOFF_RESET_5V}).

Are you using a revision 1/2 chip or an older engineering version? Can you check if the workaround in errata 89 affects your current?
For UARTE0:

*(volatile uint32_t *)0x40002FFC = 0;
*(volatile uint32_t *)0x40002FFC;
*(volatile uint32_t *)0x40002FFC = 1;

For UARTE1:

*(volatile uint32_t *)0x40028FFC = 0;
*(volatile uint32_t *)0x40028FFC;
*(volatile uint32_t *)0x40028FFC = 1;

Best regards,
Jørgen