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Original question:

Decreasing BLE signal range on cc2640r2f

Decreasing BLE signal range on cc2640r2f

jack daniels
Prodigy 90 points
Other Parts Discussed in Thread: CC2640

Hi,

Related to the decreasing range question.  Can you tell me how that will affect the power consumption of the device?  I am looking for a part that operates at about 1m and will consume on average current less that 2uA.  I realize there are a lot of related parts to this but as the transmitter receiver tend to eat a lot of the power budget, I like to try and figure out options.

Thank you

  • 0
    TI__Guru 56215 points
    Hi,

    If you lower your connection interval, then you will be able to achieve low average current consumption even with 0dBm power.

    Can you specify your user case, so we can better assist you?
  • 0 in reply to Christin Lee
    Prodigy 90 points

    Hi Christin,

    Thank you for your reply.

    Basically, I am looking at a replacement for an implantable device that currently uses NFC.   I would like the range to be about 1-2m.  The other requirement is the average current draw for at least 10years needs to be about 2uA.  The device will primarily be in sleep state and will wake up occasionally to take data.  So what I am currently doing is trying to work backwards to see if a) this is possible and if so b) what my connection interval can be.  (This is in an early stage and I am not necessarily married to this device or ever BLE so any suggestion's as to other devices would be appreciated.  But, with those I would have similar questions).

    In very very over simplified terms and ignoring a lot of other factors.

    In sleep mode the device draws 100nA.  Assuming we have a 270mAh battery that's  8.76mAh over the 10years leaving 261mAh.  The CC2640 uses approximately 6ma in 0dBm transmit and in receive mode so at 6mA that leaves about 43.5 hours of operation or about .0118 hrs/day for transmit/receive operations.

    So my questions are:

    -  How low can I drop the transmit power and what is the corresponding drop in transmit current?

    -   Is it also possible to drop the receiver sensitivity and if so what is the drop in receiver current?

    Then if I have that I can add in a budget for the rest of the circuit and estimate my path loss and create a table incorporating distance, power and connection interval.

  • 0 in reply to jack daniels
    TI__Guru 56215 points

    To answer your questions first:

    1. Yes, you can lower the TX output power to get lower current consumption. However, we do not have current number for TX output power other than 5dBm and 0dBm.

    2. No, there is no method to lower RX current.

    I would first recommend you to take a look at our Measuring Bluetooth Low Energy Power Consumption application report to get a better overview of BLE technology current profile.

    The average current consumption for 1s connection interval is 10uA, if you incorporate the slave latency with even longer connection interval, then achieving 2uA current consumption with device stays in connected is definitely no problem.

    We have a online tool called BLE power calculator for you to checkout your use case and we will also have a excel sheet version of BLE current calculator available for public soon.

    I did a quick check out if device only sends out 1 byte of data in connection and broadcast 1 byte of data (both activities stay on 30 mins per day), then this is the current consumption is gonna be like:

  • 0 in reply to Christin Lee
    Prodigy 90 points
    Thanks Christin,
    One further question. You say you only have current consumption for TX down to 0dBm. But, what is the lowest the level the TX can be set to within the device?

    And, I tried accessing the link for the power calculator which came up in German but only had the heading at the top of the page
    "Bluetooth / Bluetooth low energy power calculation tool" but then just a blank frame underneath it and little lower on the page a "Videos" heading with nothing underneath that.
  • 0 in reply to jack daniels
    TI__Guru 56215 points
    Please try this link.
    www.ti.com/.../power-calculator.page

    The lowest TX output power can be set to -21dBm.
  • 0 in reply to Christin Lee
    Prodigy 90 points
    Thanks Christin,
    For some reason it still would not appear in explorer. I switched over to google chrome and now it works.