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Circuit Design Problem

Xiaochuan WEI
Prodigy 130 points
Other Parts Discussed in Thread: CC2540

Hi ,

I want design a circuit depends on the USB dongle and Keyfob reference, in this design the space and power consumption are important. I saw that in the usb dongle design, it use one component instead of many resistors and capacitors in the Keyfob design for the antenna circuit, are these two part for the antenna in Keyfob and Dongle switchable? For the power consumption consideration I need add a 32K Hz crystal, right?

  • 0
    TI__Genius 12545 points

    Yes. You can use the chip balun for the CC2540. It does replace the discrete components required to form the balun and filter matching.

    Try these balun options

    http://www.ti.com/litv/pdf/swra380a 
    or
    http://www.ti.com/litv/pdf/swra297a

    The sleep crystal (32 kHz) can be omitted for extra savings in space and bom cost. There is an internal 32kHz clock which would be used rather than the 32kHz crystal oscillator

  • 0 in reply to Chatto
    TI__Genius 10955 points

    Chatto said:
    The sleep crystal (32 kHz) can be omitted for extra savings in space and bom cost. There is an internal 32kHz clock which would be used rather than the 32kHz crystal oscillator

    Note that if you omit the 32 kHz crystal, you will not be able to use low power modes while in a BLE connection. The 32 kHz crystal should therefore always be present for applications where low power is important.