CC2650: Use of RX_TX pin

Tony Waria

Part Number: CC2650

I don't see a detailed explanation on the RX_TX pin in the datasheet, other than the description: Optional bias pin for the RF LNA.

Is this a digital or analog I/O? How does it work in the reference circuit below, which doesn't appear to have an external LNA.

Appreciate any input from the forum.

over 8 years ago

0 A. Rebel over 8 years ago

TI__Genius 11740 points

Hi Tony,

There's some documentation on http://www.ti.com/ble-wiki under Design Resources, CC26xx RF Frontends and Antennas

Regards,
Rebel

0 Fredrik K over 8 years ago

TI__Guru** 106705 points

Hi Tony,

RX_TX is an analog pin controlled directly from the RF Core. It is used to put DC bias on the (internal) LNA inputs. In other words, a DC voltage is applied on RF_P and RF_N through L21. With internal bias, an internal inductor is used instead, and that reduces sensitivity somewhat.

Note that there are some applications, usually for CC13xx, where RX_TX can be used as a semi-digital pin to control for example external RF switches.

Cheers,
Fredrik

0 Tony Waria over 8 years ago in reply to Fredrik K

Intellectual 610 points

Hi Fredrik,
Thanks for the info. Now I understand how it works. I'm equally interested in its usage on CC13xx chips. I went to the same Wiki page as listed by Rebel, but found very limited info on the CC13xx. Do you know if there is a similar page for the sub-GHz like the one for BLE, http://www.ti.com/ble-wiki, which has very extensive coverage of various topics?
Our final design will be with CC13xx.
Thanks,
Tony

0 Fredrik K over 8 years ago in reply to Tony Waria

TI__Guru** 106705 points

Hi Tony,

For CC13xx related questions I recommend you to post on one of the other forums, Proprietary 2.4 GHz for example. There you will get support from the CC13xx experts.

Cheers,
Fredrik

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CC2650: Use of RX_TX pin