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Using a function generator rather than a TCXO with the CC1120

Elliot Taylor
Prodigy 80 points
Other Parts Discussed in Thread: CC1120, CC1125

Hi,

I was wondering if it was possible to use a function generator to input a sine or square wave through a series capacitor into the CC1120 EXT_XOSC pin rather than a TCXO? I know the datasheet says the TCXO uses a clipped sine wave, does this mean a function generator cannot be used?

Many thanks

Elliot

  • 0
    Prodigy 100 points
    Hi Elliot,
    I believe you can use pure sine wave as well...clipped sine wave is only used to reduce harmonics, not so as a mandatory waveform .
    Nir
  • 0 in reply to Nir Barak
    Prodigy 80 points

    Thank you for the reply! Another concern I have with using a function generator is that the data sheet for the cc112x says this:

    "If a TCXO is used, the CC1125 device automatically turns on and off the TCXO when needed to support low-power modes and Wake-OnRadio operation." 

    How does this turning off of the TCXO work? What would happen in terms of this when a function generator is used in its place?

    Many thanks

    Elliot

  • 0 in reply to Elliot Taylor
    Prodigy 100 points

    Well...I'm guessing the CC1125 doesn't actually turn on/off the external TXCO, maybe it is done by controlling the internal XOSC block

    But again, it's just a guess :)

  • 0 in reply to Nir Barak
    TI__Guru**** 317180 points
    You can use a function generator as long as the generated signal is according to the CC112x datasheet. Note if a squareware is used a series cap should not be used.

    It is possible to output a signal on a GPIO (see table 10 in the UserGuide) that could be used to turn a TCXO on/ off according to the state of the radio