nRF52805 BLE radio current consumption specifications

[snygaard]

Hi

We have been using the Online Power Profiler to estimate the current draw from nRF52805 during BLE activity. Especially estimating the potential peak current draw (from a primary battery cell).

But the only formal requirements present is the “Product Specification nRF52805 v1.3”.

 A number of questions appear:

1) nRF52805 cannot be selected as chip in the online tool. If choosing nRF52810 instead, is the characteristics then similar to nRF52805?

 

2) In “Product Specification nRF52805 v1.3” section 5.2.1.3, some figures for radio transmitting/receiving current consumptions are present.

We try to relate the product specification values to what we can expect from our design, but to do that, we need to know all the preconditions. Some are stated (3V, DCDC, data rate etc) – some are not.

We can play with the Power Profiler tool, but the product specification is the only formal specification we can rely on.

We wonder what the more detailed BLE conditions are – to get the numbers in the product specification, and what the numbers represent.

a)

Specific, what BLE conditions are used to specify I_{RADIO_TX2}?

Is it a kind of continuous transmitting mode, with the transmitter literally transmitting continuously (no RX active)?

Or is it running with TX burst at certain on/off timings?

Or is it running in Advertising (TX only or TX/RX) mode with presumed payload and advertising interval?

Or something else?

b)

The number present ("typ 5.8mA"), does this only cover the BLE radio part? (Any MCU operation to be added)

c)

The number present ("typ 5.8mA"),  is this the peak current during a single TX burst? Or the average current during multiple TX burst? Or something else?

Please clarify.

[Stian Røed Hafskjold]

Hello

The Online Power Profiler (will call it OPP from here) is created as a supplement to the product specification, since the BLE specification and the resulting current consumption relies on too many parameters to document using only tables. The OPP will include all CPU processing, HF clock current, etc needed for the nRF5 to stay in either BLE advertising, or BLE connected mode.

1)

You can select the nRF52810 in the OPP, as the radio characteristics and current consumption are almost identical to the nRF52805.

2a)

The numbers in the data sheet correspond to a continuous transmitting or receiving mode, no bursts or on/off timings. Just the run current of the radio configured in continuous TX or RX with the radio parameters needed for BLE communication, like the bit rate and the external HF clock needed for accuracy. It's not related to the link layer defined in the BLE specification, where the radio is turned on and off to create advertising or connection modes/packets.

2b)

Yes, it only covers the radio in transmitting mode. Any CPU processing must be added.

2c)

It's the peak current during a single TX burst.

I hope this answers your questions. I understand that you can only consider the product spec as the formal documentation, but unfortunately we do not document specific BLE scenarios like "Advertising 100ms, 10B payload, 1.8V, DCDC on, etc". Instead we refer to the OPP. 

Of course we can provide you with measurements on the nRF52805 with which ever BLE parameters you are interested in, if that helps.

Best regards,
Stian

[snygaard]

Thank you for the clarification.

Best regards,
Sten