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CC2500: CC2500 (and similar) AGC Control

Dave Delage
Intellectual 480 points
Part Number: CC2500

I would like the receiver to be at a fixed sensitivity without AGC control.

According to the datasheet on Page 77, setting AGCCTRL0.AGC_FREEZE[1:0] to 3(11) "Manually freezes both the analog and the digital gain settings. Used for manually overriding the gain." So that freezes the gain as some fixed level. 

But, what sets the gain?

Thanks,

Dave

  • 0
    TI__Mastermind 39860 points

    There is absolutely nothing to gain from freezing the AGC. This feature is added for test purposes only. With the AGC free-running the gain will always be at maximum when entering RX and the gain will be automatically adjusted so that the signal level internally will be at a value set by MAGN_TARGET. This ensures sufficient SNR and operation within the ADC input dynamic range. 

    If you still want to set the gain manually you need to use register AGCTEST (address 0x2B)

    AGCTEST[7:6]: First LNA gain. max gain: 00, medium gain: 01, min gain: 10

    AGCTEST[5:3]: Second LNA gain. max gain: 111, min gain: 000

    AGCTEST[2:0]: Digital gain. max gain: 111, min gain: 000

  • 0 in reply to Sverre
    Intellectual 480 points
    Thank you so much. It's always refreshing when someone answers the actual question asked even if the answer is you probably don't want to do this. While I have designed several circuits using the CC2500 in one of the ways for which it was intended, my current project envisions using it in a way that was probably not considered by its designers. Because that way is modestly proprietary, is it possible to ask you a question off line?
    Thanks again,
    Dave
  • 0 in reply to Dave Delage
    TI__Mastermind 39860 points

    Send me a friend request and we can handle this off-line