CC110x Balun at 433.92MHz

Byron Loader

Other Parts Discussed in Thread: CC113L

Hi All,

I am implementing the Balun @ 433.92MHz for the CC113L as per the values used in the reference design.

As per DN17 there is the following sentence "The balun in the 315 and 433 MHz reference design are not matched to 50 Ohm, it is only the antenna output which is matched to 50 Ohm in these designs."

Can someone supply the balun unballanced impedance (at the balun output) so I can verify my design.

Regards

Byron

over 10 years ago

0 TER over 10 years ago

TI__Guru**** 317180 points

If you use www.ti.com/.../cc113lem-433-rd you will get a balun/ filter with a 50 ohm point at the SMA connector. I don't see the need of using DN017 here?

0 Byron Loader over 10 years ago in reply to TER

Prodigy 140 points

We implemented the development board and the output does not appear to be 50R (66+J10). If I add the filter components after the balun (L123, L124, C123, C125) I get very close to a 50R match.

0 TER over 10 years ago in reply to Byron Loader

TI__Guru**** 317180 points

Do you have a schematic showing what you implemented when you measured 60+j10 and how you measured this?

0 Byron Loader over 10 years ago in reply to TER

Prodigy 140 points

We measured at the point marked "A" with R2 and R3 out of circuit using a HP network analyser. We measured 66+J10 at this point. We used a smith chart to calculate that the added filter approximated 50R

0 TER over 10 years ago in reply to Byron Loader

TI__Guru**** 317180 points

I assumed that the reference design for CC113L has a 50 ohm termination but I see now why you asked the question you did.

No, we don't have an impedance number for the 'A' position. Normally a LNA has a fairly wide optimal source impedance (wide circle in the smith chart) and we get good performance with the BOM in the reference design. Eq it should not be required to convert this to 50 ohm.

Sub-1 GHz

Sub-1 GHz forum

CC110x Balun at 433.92MHz