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Regarding TRX_SW pin in CC1120/CC1121

HNRFGUY
Intellectual 320 points


Hello,

I know that TRX_SW pin is going low at TX,  to shunt the PA transmit energy away from the LNA while the PA is on.

I have 2 questions:

1. Does the low impedance at TRX_SW pin "rotates" on the Smith chart to present the TX path high impedance or is it only shunting the energy from the LNA?

2. If the LNA is at "OFF" mode during TX, how can it get damaged by the PA  power (its only 14 dBm) ??

Regards

Haray

  • 0
    TI__Guru**** 317180 points
    1) The TRW_SW is connected internally in the chip to the drain on a NMOS (source to gnd). The purpose is not to source energy away, it's to give the optimal load impedance.

    If you have separate Rx and Tx path you don't have to use the TRX_SW pin.

    2) Not sure if I understand your question?