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TRF372017: TRF372017 VCM setting

Hiroyuki Yamada
Prodigy 40 points
Part Number: TRF372017
Other Parts Discussed in Thread: DAC3484

I have a question regarding the TRF37201 VCM.

The datasheet indicates that when using the internal VCM, the BB input should be AC coupled. In this case TRF37201 settings would be the following:

PWD_BB_VCM=0
　VREF_SEL_n=0～7(Default 4)


　If using Offset adjustment
　PWD_DC_OFF=0
　IOFF_n=0～255(Default 128)
　QOFF_n=0～255(Default 128)

 

If the VCM is generated externally, the datasheet only shows a sample circuit that uses the BB input with DC coupling, with a description of setting the VCM to 1.7V, but there is no description of the IC settings.

Could you provide the settings for PWD_BB_VCM and PWD_DC_OFF when VCM is supplied externally?

  • 0
    TI__Guru 66004 points

    Hi,

    Please find attached app note for DC coupling interface of DAC to TRF372017.

    You will need to make sure PWD_BB_VCM is set to 1 to turn off the VCM. PWD_DC_OFF is for DC offset correction, which can be available as a DAC feature such as the DAC3484. Thanks

    -Kang

  • 0 in reply to Kang Hsia
    Prodigy 40 points

    Thank you for your reply.

    Please let me know if my understanding is correct.

    　1) When using TRF372017 with DC coupling, it is necessary to set PWD_BB_VCM=1.

    　2) PWD_DC_OFF is for offset correction and can be used without issue, including when TRF372017 is used with DC coupling.

    Thank you.

  • 0 in reply to Hiroyuki Yamada
    TI__Guru 66004 points

    Hi Yamada-san

    Hiroyuki Yamada said:
    1) When using TRF372017 with DC coupling, it is necessary to set PWD_BB_VCM=1.

    Yes

    Hiroyuki Yamada said:
    2) PWD_DC_OFF is for offset correction and can be used without issue, including when TRF372017 is used with DC coupling.

    Negative. The DC offset correction must be used with the internal TRF372017 VCM enabled and AC coupled mode. If you chose to DC couple, you must use external DAC QMC feature to adjust for the LO offset.

    -Kang

  • 0 in reply to Kang Hsia
    Prodigy 40 points

    Thank you for your response.

    Please let me know if the following is correct.

    1) When TRF372017 is used with DC coupling, both PWD_BB_VCM=1 and PWD_DC_OFF=1 need to be set.

    2) For DC coupling, since it is necessary to adjust the LO offset using the external DACQMC feature,

         does this mean that the LO is supplied from an external source instead of the internal VCO?

         Could you tell me which bit address needs to be set in order to do this?

    Thank you.

  • 0 in reply to Hiroyuki Yamada
    TI__Guru 66004 points

    Hi

    Hiroyuki Yamada said:
    1) When TRF372017 is used with DC coupling, both PWD_BB_VCM=1 and PWD_DC_OFF=1 need to be set.

    Only PWD_BB_VCM = 1 is needed. The PWD_DC_OFF = 1 is optional as discussed earlier.

    Hiroyuki Yamada said:
    For DC coupling, since it is necessary to adjust the LO offset using the external DACQMC feature,

    yes, correct

    Hiroyuki Yamada said:
    does this mean that the LO is supplied from an external source instead of the internal VCO?

    It is a don't care. LO correction can apply to both externally sourced VCO or internal VCO. 

    For external VCO, if you choose to use it, here are the instructions:

    -Kang

  • 0 in reply to Kang Hsia
    Prodigy 40 points

    Thank you for your response.

    Please let me know if the following is correct.

    1) Is it the case that PWD_DC_OFF is valid only when PWD_BB_VCM = 0, so when PWD_BB_VCM=1 then it is the same as if PWD_DC_OFF=1 regardless of the status of PWD_DC_OFF?

     

    2) Understood that the LO offset adjustment is applicable regardless of the LO source. Can you tell me the bit address to set when adjusting the LO offset when using the internal VCO?

    Thank you.

  • 0 in reply to Hiroyuki Yamada
    TI__Guru 66004 points

    Hi

    Hiroyuki Yamada said:

    1) Is it the case that PWD_DC_OFF is valid only when PWD_BB_VCM = 0, so when PWD_BB_VCM=1 then it is the same as if PWD_DC_OFF=1 regardless of the status of PWD_DC_OFF?

     

    No, PWD_DC_OFF is independent of PWB_BB_VCM. However, we do not recommend using TRF372017 internal DC offset when it is DC coupled. We recommend using DAC QMC feature.

    Hiroyuki Yamada said:
    2) Understood that the LO offset adjustment is applicable regardless of the LO source. Can you tell me the bit address to set when adjusting the LO offset when using the internal VCO?

    You may refer to the section below. It is common to both ext VCO or int VCO mode.