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TRF370417: Differential input impedance

Part Number: TRF370417
Other Parts Discussed in Thread: DAC3484, DAC38J84, TRF3705, DAC5687, DAC5688

To whom it may concern,

According to the data sheet, TRF370417's two BB inputs have single-ended input impedance of 5kOhm. 

I wonder if the differential input impedance is 100ohm. 

If the BB inputs are high impedance, then why doesn't the TRF370xEVM have any 50ohm termination at the BB input ports? 

Please help. 

Best,

Weiyu

  • Hi Weiyu,

    You are correct that the input impedance for baseband of TRF370417 is high impedance.

    I see some of the newer EVMs such as TRF3705 EVM have 50ohm mounted to the baseband input since it was designed to match well with current source DACs like the DAC3484 and DAC38j84. 

    I believe at the time most of the interface to the TRF370417 is through the current sink DACs such as DAC5687 and DAC5688 where some sort of level translation network from 3.3V to 1.7V is required. Hence, the team did not mount the 50ohm load termination. See below pictures found on the TRF370417 EVM.

  • Hi Kang,

    Thank you for your help!

    Weiyu