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How to get maximum coin cell battery life in CC2650

Dnyaneshvar s
Intellectual 571 points
Part Number: CC2650

Hello,

I am using CC2650 custom PCB

BLE SDK 2_02_07_06

CCS7.4

Compiler TI v5.2.6.

I have developed application code which can receive data over BLE (with reference to the Simple BLE peripheral example code).

We have developed our own PCB design which also works fine. I am driving display with CC2650 which updates only when BLE Central sends the data. Otherwise I put this display in Sleep mode.

Now coming to the battery life.

Our product will be running on coin cell and I wanted to know that for how many years my device will work on CR2450 coin cell (620mAH capacity of this cell)

I have done some power analysis with Nordic power profiler PPK2 and attaching screenshots of the same.

I have changed advertising interval from 100ms to 5Seconds

also, in my code I have changed this values to increase the data reception time

#define DEFAULT_DESIRED_MIN_CONN_INTERVAL     4 

#define DEFAULT_DESIRED_MAX_CONN_INTERVAL     20

Aa of now The Device Average current is 19.98 uA (micro Ampere) for 1 minute of duration

So if I calculate the Battery Life of my device with above data

19.98uA  = 0.01998 mA (milli Amp) for 1 minutes

0.01998 * 60 Minutes  = 1.1988 mA for 1 hour

(CR2450 battery is 620mAH capacity)

620 mAh / 1.1988 mAh = 517.183850 hours

517.183850 / 24 hrs. = 21.54 days.

So my first question is

Is above calculations are correct ?

--------------------------------------------------------------------------------------------------------------------------------------------------

My other question is If I zoom into the waveform of power analyzer, between two advertising events there is some other power consumption taking place

(screenshot attached below)

As seen in Image there is some current of 50 to 55 uA and also there is current that never goes below 20 uA (microamp).

(If I disconnect the E paper, then also this current is present. So it is not being consumed by the E-paper)

Till now this is Unknown current to me

Second question -

Can you please guide me what is the source of this unknown current?

-----------------------------------------------------------------------------------------------------------

As per datasheet, standby current is 1uA.

Please guide me How can I reduce my device current to 1uAmp

Thank you

Dnyaneshvar

  • 0
    TI__Guru**** 217617 points

    Hello Dnyaneshvar,

    Have you reviewed SWRA478 and SWRU393?  These each provide helpful Power Management advice.  There is also the Power Management User's Guide to consider.  Furthermore, would you be able to evaluate the Pin Standby example to confirm that your device is capable of reaching the targeted 1 uA and that there is no leakage current from hardware?  Likewise, are you able to evaluate power consumption using a CC2650 LaunchPad or SensorTag to create a baseline? Next, the datasheet provides peripheral current consumption in Section 5.4 and the TRM provides recommendations for Unused I/O pins in Section 11.6 to avoid pin leakage.  Please consider these points while further evaluating the power consumption of your system.

    Regards,
    Ryan

  • 0 in reply to Ryan Brown1
    Intellectual 571 points

    Hello Ryan,

    Thank you for you detailed answer.

    I will go through the suggested resources on power management and get back here.

    But please guide me on these calculations,

    AVERAGE CURRENT FOR 1 MINUTES IS 19.98uA  = 0.01998 mA (milli Amp) (AS PER SELECTION IN PROVIDED SCREENSHOT)

    0.01998 * 60 Minutes  = 1.1988 mA for 1 hour  --- >    is this step really required?

    620 mAh / 1.1988 mAh = 517.183850 hours

    517.183850 / 24 hrs = 21.54 days.

    Is it required to multiply 1 minutes average current(0.01998 mA) with 60 minutes before division with 620mAh?

  • 0 in reply to Dnyaneshvar s
    TI__Guru**** 217617 points

    If you have a 620mAh battery and your average device operating current is 19.98 uA then the total number of hours the device can run off the battery is 620 mAh / 0.019 mA = 32,631 h = 1,357 days.  The total will be reduced when accounting for regular BLE communication over the device's lifetime, and you can determine the best output TX power for an optimal tradeoff between power consumption and performance

    Regards,
    Ryan