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CC2340R5: Coin Cell Operation - State of Charge and Power Consumption Algorithms

Til Schoengarth
Prodigy 720 points
Part Number: CC2340R5


Tool/software:

Hi team,

do we have experience with algorithms to determine the state of charge of coin cells such as CR2032, as well as power consumption algorithms?

I know there is the BT Power Calc tool, we have the XDS110-ET for power consumption during development but I am talking about production.

I know there is the Battery Monitor integrated into the CC2340 to measure voltage and temperature, but do we have an algorithm to determine state of charge based on these results? And can we estimate power consumption during runtime in SW or is a external current sense needed?

I saw there are some reference designs with older devices, i.e. 

TIDA-00759 reference design | TI.com

https://www.ti.com/tool/TIDA-00374

TIDA-00756 reference design | TI.com

I cannot open the firmware because it gets blocked by security, so not sure if there are useful algorithms for the application.

Do we have similar reference designs for CC2340?

Best regards,

Til

  • 0
    TI__Mastermind 35070 points

    Hi Til,

    This is a great question. From the perspective of our device, we typically estimate battery life through dividing nominal battery capacity by average current consumption -- therefore to increase battery life, we design the code to use the lowest current consumption while still achieving the application functionality requirements.

    Regarding algorithms to track the battery at run time, this is highly dependent on the battery itself -- vendor, chemistry, etc -- so there is no one-size fits all algorithm.
    The simplest (and low cost) method would be to use Battery Monitor which checks voltage of the battery. Then convert voltage to estimated charge remaining -- battery datasheet should have some graph estimating the remaining charge in the battery based on voltage.

    Thanks,
    Toby

  • 0 in reply to Toby
    TI__Prodigy 720 points

    Thanks Toby,

    usually how do you determine the average current consumption during runtime?

    And which more complex algorithms do you suggest? Does TI have example algorithms? This would be for standard coin cells such as CR2032/CR1620/CR1632

  • 0 in reply to Til Schoengarth
    TI__Mastermind 35070 points

    Hi Til,

    The average current consumption from our device perspective is calculated during development/QA phase of the customer application.

    For an example algorithm, the main one I'm aware of is the on-chip Battery Monitor method.
    With this method, the battery datasheet (e.g. cr2032.pdf) would be referenced, specifically the "Discharge" graphs. Then when device Battery Monitor sees a certain voltage, it could have some lookup table based on the battery datasheet to estimate remaining charge. (e.g. for CR2032 if device reads 2.5V, likely 10-20% capacity left, at 1.8V this reaches close to the brownout of the device whose minimum supply voltage is 1.71 V per datasheet).

    Battery Monitor can interrupt based on a low voltage threshold (see BatteryMonitor_registerNotifyLow).

    Thanks,
    Toby