CC1310: Disable external bias circuit

Devin Murphy

Part Number: CC1310

For this question I am going to refer to component designators and signal names from the LAUNCHXL-CC1310_1_3_0_Schematic.pdf.

The LAUNCHXL-CC1310 is obviously configured for external bias since it has L22 populated and RX_TX is connected. To disable the external bias circuit, is it sufficient to depopulate L22 and in firmware configure for internal bias? Or does the RX_TX line have to be disconnected as well? It seems like it would be better to disconnect RX_TX but it isn't clear to me whether disconnecting it is required since a quick test that I did on our own hardware seems to have worked. We do not want to send such a design to production if there is a strong possibility leaving the RX_TX line connected will cause problems.

Thanks for any assistance!

over 8 years ago

0 TER over 8 years ago

TI__Guru**** 317180 points

Follow fig 7.1 in www.ti.com/.../cc1310.pdf for the hardware side.

0 Devin Murphy over 8 years ago in reply to TER

Intellectual 430 points

I am familiar with this figure, but it only says RX_TX is "not necessary" it does not say "must be disconnected". My question is must RX_TX be disconnected for internal bias to work properly?

0 TER over 8 years ago in reply to Devin Murphy

TI__Guru**** 317180 points

I would disconnect it to be safe. I have not looked at the schematic how this is connected internally.

Do you want to convert a differential design to a single ended design?

0 Devin Murphy over 8 years ago in reply to TER

Intellectual 430 points

That is what I thought.... we were hoping to avoid changing our design at this point but we will if necessary.

Yes, our balun / filter circuit follows the TI reference designs to connect to a single ended antenna. For different reasons we do not want to use the Johanson IPC with this design.

0 TER over 8 years ago in reply to Devin Murphy

TI__Guru**** 317180 points

Why do you want to go single ended if you have a differential design today?

Could you disclose some of the reasons why you don't want to use an IPC?

0 Devin Murphy over 8 years ago in reply to TER

Intellectual 430 points

Sorry I think we misunderstood each other. Our design is already using a single ended antenna. What we are discussing is using internal bias instead of external bias, but the design does not currently have any way of physically disconnecting the RX_TX line. That is why, if that is required, we will have to change the design.

0 Devin Murphy over 8 years ago in reply to TER

Intellectual 430 points

The main reason is cost, we are trying to save every penny we can. Secondarily we have seen generally higher TX current draw when using the Johanson IPC on other designs. While achieving the same output power, the Johanson IPC was found to draw approximately 20% more current.