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LMX8410L: Internal gain

Cherry Zhou
Mastermind 22235 points
Part Number: LMX8410L

Hi Team,

1) Is the total gain of the LMX8410L shown in the following table? It appears that the internal gain did not reach this value during testing.

2) Is the internal integrated if amplifier controllable? If so, what are the relevant registers? 

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Guru* 93670 points

    Hi Cherry,

    try to see if R105[4:2] can change the gain of the LNA. Default value is 7, smaller value = higher current. 

  • 0 in reply to Noel Fung
    TI__Mastermind 22235 points

    Hi Noel,

    Thank you for the support.

    May I know why does TICs PRO not have this register? If R105 controls the internal LNA gain, what is the range of the control gain? 

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Guru* 93670 points

    Hi Cherry,

    That is a hidden register which is used to control the current of the LNA, l do not know if it can be used to change the gain of the LNA, just give it a trial.

  • 0 in reply to Noel Fung
    TI__Mastermind 22235 points

    Hi Noel,

    The customer has tried to change the R105 register, but the gain has not changed significantly.

    1) According to the manual, the voltage gain is 9dB at 8GHz RF input, but in reality, at 8GHz RF input, the measured gain is approximately -10 dB at the internal LO of 9 GHz and 1GHz if output, which is quite different from the manual. What is the internal gain of the lmx8410l? Is it possible to configure it?

    2) Why is there a local leakage on the output of the local oscillator in the mode where the register is configured as Internal LO Poly to M? This mode should be where the local oscillator mixes internally, right?

    3) LMX8410L has an internal LNA and if amplifier IFA, are the two amplifier gains controllable?

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Guru* 93670 points

    Hi Cherry,

    If R105 dose not help, I don't have other means to change the voltage gain. 

    At GHz frequency, leakage is unavoidable especially when everything is packaged in a small die.

    If register maps does not contain amplifier gain setting, that means it is not available or if hidden register exist, that means we do not expect the gain needs user configuration.