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CC2640R2F: Lowering Peripheral Peak Current while Connected

Ali Mirzazadeh
Intellectual 450 points

Part Number: CC2640R2F
Other Parts Discussed in Thread: CC2640,

Hi,

I've been power optimizing my CC2640 and noticed that my peak power consumption was 14mA and happens at every connection interval. My goal is to reduce this to 5mA or as close to this level as possible (I realize signal strength will probably suffer). My original suspicion was to reduce the TX power of my program, which I do by calling HCI_EXT_SetTxPowerCmd(HCI_EXT_TX_POWER_MINUS_21_DBM); just before I begin advertising. However, even though I believe the default for this is 0dbm I did not notice much of a difference in the peak power consumption between the two (still at 14mA). I'm wondering if I'm doing this correctly or if it's silently failing? Because I'd imagine the difference in signal strength at the very least, if not the current consumption, should be stark. For context, I'm using Single Ended Internal Bias antenna with a crystal-less setup.

UPDATE: We believe the peak might actually be a result of the RX phase and not the TX phase. Is there any way to reduce the peak current for the RX?

Thanks!

Ali

SDK Version: 4.10.00.10

Chip: CC2640R2F

  • 0
    Guru 735695 points

    Try to refer to Measuring Bluetooth Low Energy Power Consumption application note and you shouldn't see 14 mA as the peak power consumption. What's your SDK version and example used for this test?

  • 0 in reply to YiKai Chen
    Intellectual 450 points

    Hi YK, thanks for your response. I'm using SDK 4.10.00.10, with Simple Peripheral connecting to Simple Central (I'm trying to optimize peripheral). Here is a couple pictures of the power charts I was referring to. This is a 1sec window, 1kB/s, with ~100ms connection interval and 128bytes per packet. The next picture I zoom into one connection event to show specific. It's strange that it looks pretty significantly different than the graphs in the link you attached, as in i'm not sure how my peaks match up to the ones in their graph.

    Thanks for your help!

    Ali

  • 0 in reply to Ali Mirzazadeh
    Intellectual 450 points

    Hi YK,

    I re-reviewed the helpful document you sent. I think I understand the problem a bit better now. The TX peak actually has lowered, but the 14mA I'm getting is actually from the RX peak. In the document, they note a 17.5mA peak for RX on page 13. So it seems like the TX power is being set correctly, but the RX is what is causing the huge peak. 

    Is there any way to reduce this RX peak? Keep in mind I have crystal-less setup with single-ended, internal bias antenna.

    Thanks!

    Ali

  • 0 in reply to Ali Mirzazadeh
    TI__Expert 5345 points

    Hello Ali,

    I am working to find the appropriate expert to help you. This may take some time to reach the right person depending on availability. Please expect an update by 7/27. I appreciate your patience.

    In the meantime, can you please clarify what processor and SDK you are using? (it's unclear if it's CC2640 or CC2640R2)

    Regards,

    Luis

  • 0 in reply to Luis M
    TI__Guru 58425 points

    Hi Ali,

    Could you supply a plot that is a bit more detailed around the peak in question? 

  • 0 in reply to IUsedToBeARealPerson (M-W)
    Intellectual 450 points

    Hi M-W, Thank you for your response. Sure, here are some more detailed pictures. They are gradually zooming in on the same peak. I've set my TX Power to -21DBM in BLE_USER_CONFIG.C and even tried using HCI_EXT_SetTxPowerCmd(HCI_EXT_TX_POWER_MINUS_3_DBM) in Simple_Peripheral.c but neither seems to make a difference for the peak that's at over 14mA. Keep in mind this is for connection event, not advertising. Thanks!

  • 0 in reply to Ali Mirzazadeh
    TI__Guru 58425 points

    Hi Ali,

    I have been asking around internally an the power numbers seems to be about what you could expect. There is many things to consider but if you take RX for example, it would account for at least 6 mA and the CM4 core (inc flash and ram and depending on what state it is in) could account for 3.5 mA more. The remaining 4 ish mA could be contributions from other parts of the system (such as RF Core and peripherals).

    I would recommend you also have a look at this application note: 

    https://www.ti.com/lit/pdf/swra478

    Typically power consumption optimization in BLE comes down to adjusting things such as MTU size and connection interval but there is many more things to consider to reach a really low average power consumption. As for your goal of "5 mA peak", this is simply not a realistic value in this case.

  • 0 in reply to Ali Mirzazadeh
    Guru 86865 points

    Hi,

    Please, refer to the HCI documentation to set the TX Power. Also you need RF tester to verify if you are actually setting the TX Power. Best, is not set the TX Power since the default is 0 DBm. You can use 0 DBm as reference for your current or power measurements.

    -kel

  • 0 in reply to IUsedToBeARealPerson (M-W)
    Intellectual 450 points

    Hi M-W, thank you for your response. That makes a lot of sense, I'm using DLE to max my MTU size so that's probably why (plus the RX, CM4 core, etc) I'm observing the peaks that I am. Thank you!

    Ali