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CC2540 vs CC2640 antenna

Brian Peavey
Prodigy 20 points
Other Parts Discussed in Thread: CC2540, CC2640, CC2650

  I'm trying to decide between the CC2540 and CC2640 for a new BLE project.  The product has only very modest performance requirements

- Respond to a periodic interrupt every 70 ms (+/- 3 ms)

- Manipulate several GPIO lines

- Occasional SPI transmissions in response to GPIO changes.

- Monitor incoming BLE traffic to change product configuration

  I also need the ability to support OAD without external flash.  I've played a little with the CC2650 development kit using the SimpleBLEPeripheral project.  It looks like the Stack + the Application for this project takes roughly 3/4 of the available 128K flash space.  Therefore, OAD will likely not be feasible.  The other constraint I have is PCB space.  I'm trying to determine the sizes of the antennas required for the 2540 vs the 2640.  Can the same (pre-qualified) antenna be used for each?  Will I get the same TX and RX performance from each given the same antenna?  Do the same antennas perform the same on each platform?

  I'm currently leaning towards the CC2540 beacause of cost, USB support, and larger flash size (to support OAD).   I believe the negatives of the 2540 (smaller RAM, less powerful CPU, BLE 4.0 vs 4.1 support) are all things I can live with for this particular project.  Are there other factors to consider when comparing these 2 platforms?  

  Thanks...

Brian

  • 0
    TI__Genius 9325 points
    Hi Brian,

    Regarding on-chip OAD, please refer to CC2640 BLE OAD User's Guide. You can get some idea, from section 8.5 of the document, about how to reduce the stack size to give more space to the application.

    Not only the differences between CC254x and CC26xx platforms you listed, there is another significant difference - power consumption. With the same batteries and the same use case scenarios, the battery with CC26xx will have much longer life than the other.

    For other questions, I will check with a hardware expert and get back to you.

    - Cetri
  • 0
    TI__Guru** 106705 points
    Hi Brian,

    The same antennas can be used for both devices. Note that the balun and RF filter circuitry is slightly different between the two.

    The RF performance is better for CC2640 with 5 dBm maximum output power and -97 dBm sensitivity vs. 4 dBm and -93 dBm for CC2540. Most BLE devices run at 0 dBm output power, and if that is sufficient for your application the CC2640 can be used with the simplified single ended output. This is not an option for CC2540.

    Another factor is of course that the CC2640 has significantly lower current consumption compared to CC2540.

    Cheers,
    Fredrik