Nordic Dongle Power Off mode

RE: Nordic Dongle Power Off mode

rananna — Thu, 07 Jan 2021 10:31:04 GMT

Thanks again for your help with this.

Great support!

RE: Nordic Dongle Power Off mode

Stian Røed Hafskjold — Thu, 07 Jan 2021 09:33:35 GMT

[quote user="rananna"]I see the reference design has it in, but would there be any downside to leaving VDDH floating and not tying it to VDD through the SB1 short? [/quote]

All I can say is that the regulator is designed this way (VDD and VDDH shorted) and all production testing we have done to verify our product is with this configuration. So we cannot guarantee that every device will work as expected without VDD and VDDH shorted. So for mass production I would definitely follow the reference design, but for prototyping and testing purposes you will probably be fine by leaving out the SB1 short.

RE: Nordic Dongle Power Off mode

rananna — Wed, 06 Jan 2021 23:27:35 GMT

Yes, I am powering on VDD out.

You were right, I did not properly disconnect SB2 on the first dongle.

When I did, the poweroff current fell to 0.5uA.

However, this was measure before I shorted SB1.

I then shorted SB1 on both boards, and there was, as expected, no difference in the poweroff current.

So , I have the answer, thank you!

I see the reference design has it in, but would there be any downside to leaving VDDH floating and not tying it to VDD through the SB1 short?

I wanted to simplify the preparation of the dongle, and leaving out the SB1 short would simplify things at little bit by only requiring the sb2 open.

RE: Nordic Dongle Power Off mode

Stian Røed Hafskjold — Wed, 06 Jan 2021 21:48:28 GMT

The VDD and VDDH should be shorted when not using the first regulator stage (following the reference design), which is what you do when you short SB1. I measured 0.4uA in System OFF with this setup.

I'm pretty sure that the extra 10 uA is due to power on VBUS_nRF, which you get rid of by cutting SB2.

So my guess is that you did not cut SB2 properly on the first dongle. And on the second dongle that has both SB1 and SB2 open, SB2 was cut properly, which gives you 0.5uA. Can you try to short SB1 on the last dongle where you see 0.5uA? It's enough to just short it with the tip of a screw driver or similar, just to test. Thanks.

If my assumption is wrong can you please tell me the dongle version number? Maybe they did some changes to the design that I'm not aware of.

And, you are powering the dongle on the pin called VDD OUT right?

RE: Nordic Dongle Power Off mode

rananna — Wed, 06 Jan 2021 13:53:39 GMT

UPDATE

the previous result was on a dongle with SB2 open and SB1 shorted.

I just tried on a dongle that has BOTH SB2 and SB1 open.

NOW I see a power OFF current of 0.5uA!

So there is some effect of the first regulator on VDDH?

RE: Nordic Dongle Power Off mode

rananna — Wed, 06 Jan 2021 13:43:42 GMT

Thanks for this. The answer certainly makes sense.

However, when I disconnected SB2 and measured again, I am still measuring about 10uA.

What did you measure when you cut SB2 on the dongle?

RE: Nordic Dongle Power Off mode

Stian Røed Hafskjold — Wed, 06 Jan 2021 10:42:16 GMT

Hi, so I tried measuring here, and I see the same 10 uA in system off.

I took a closer look at the schematic and you actually have to cut SB2 when powering only on VDD. Otherwise VBUS_nRF will be powered as well, and this is where the leakage occurs. VBUS_nRF should only be powered when the USB is in use, otherwise the USB peripheral will be consuming current. From the spec:

Symbol	Description				Min.	Typ.	Max.	Units
I_{USB,DISABLED,VDD}	Current from VDD supply, USB disabled, VBUS supply connected, 256 kB RAM retention, regulator=LDO, CPU sleeping				3	7	11	µA

https://infocenter.nordicsemi.com/topic/ps_nrf52840/usbd.html?cp=4_0_0_5_34_13#unique_518559908

RE: Nordic Dongle Power Off mode

rananna — Tue, 05 Jan 2021 15:12:38 GMT

I am not using the usb port at all.

I have connected the coin cell to the VDD out pin, and have soldered SB1 to short VBUS to VDD OUT.

Yes the debugger is not connected, and the board has been reset.

I created a main() that simply immediately goes into poweroff mode by:

sd_power_mode_set(NRF_POWER_MODE_LOWPWR);

so no other functions are called

Is the S340 softdevice is drawing power when it is in poweroff mode?

Can you try this on your bench with a dongle and see what you measure?

RE: Nordic Dongle Power Off mode

Stian Røed Hafskjold — Tue, 05 Jan 2021 14:53:18 GMT

Hi, there are not that many components on the dongle that can leak current really, so I'm not sure. Did you disconnect the debugger when you measure current?

I assume that you unplug the dongle from the USB port when you power it with a coin cell battery, as you cannot use both at the same time.

When you are not using the first regulator stage (high voltage mode) you should connect VDD and VDDH together. You can do this by soldering SB1. You should at the same time open up SB2, because if you connect the dongle into a USB port while SB1 is shorted, the chip will be bricked. So, if you open SB2 the USB power will be disconnected from the dongle, and you're safe.

RE: Nordic Dongle Power Off mode

rananna — Mon, 04 Jan 2021 18:54:32 GMT

update:

I ran the same code on a nrf52840DK and got under 1 ua current.

It seems that maybe there is a component on the dongle that is leaking current?