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TRF371109EVM: function/purpose of BUF in register 1 of TRF3711XX device.

Part Number: TRF371109EVM

The TRF3711 EVM user guide describe the BUF Pwd (power down) register as :

Enables power down on test buffer for mixer output; default is powered down.

Is this feature usable for the end user?

If so, what does it really do, a schematic showing the circuits with in and out ports will be very useful.

  • Hi Juswanto,

    The buffer provides impedance isolation. For example, if you like to connect another device such as ADC to the mixer output of TRF3711, the buffer isolates the output impedance of the demodulator from the input impedance of the ADC. Without the buffer, you will have to match the mixer output impedance to the ADC input impedance for maximum power transfer.

    Thanks,
    Eben.
  • In reply to Ebenezer Dwobeng:

    Eben:

    The mixer output is in DC to 16MHz or so frequency range.
    Most ADCs have high input impedance, like the ones I am using is in the giga ohms.
    What is the mixer output impedance?
    What is the BUF output impedance?
  • In reply to juswanto wardojo:

    Hi Juswanto,

    Output impedance is 1kohm(resistance), 20pF(cap)
    The buffer also provides support for a wider range of common mode voltages. If you were to connect to the mixer output directly, you will need to make sure the common mode voltage is 1.5V. With the buffer, common mode voltages between 1.5 to 2.8V can be supported through the VCM pin.

    Thanks,
    Eben.
  • In reply to Ebenezer Dwobeng:

    If you are referring to the MixI/Qoutp/n ports then these give access to the demodulator output before going through the BB gain and filter path. The Buf_Out is normally powered down to disable these ports. Those ports are usable, however, they are not tested so performance metrics are not guaranteed. The output BW of these ports is limited by the buffer bandwidth which is somewhere around 25 - 30 MHz. The ports require a high impedance load and operate with a nominal 1.5V common mode voltage similar to the normal BB outputs. Utilizing these ports yields a gain around 10 dB (frequency dependent).

    --RJH
  • In reply to Ebenezer Dwobeng:

    Thanks Eben.

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