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LAUNCHXL-CC13-90: CC13xx with external oscillator

Part Number: LAUNCHXL-CC13-90

I wanted to just follow up on this thread and ask a couple of questions:

CC13xx External 24 MHz Lock - Sub-1 GHz forum - Sub-1 GHz - TI E2E support forums

I have an application that requires 2xCC1310s to be synchronized so that I can produce 2 CWs in the range of 880-890 MHz that are frequency-aligned.

In order to do that I needed the reference clock of both CC13xx to be common.

As stated in the E2E forum though (see above) this is out of spec. I thought of giving it a shot even though it is out of spec because I really like the CC and I also have a hard requirement for frequency alignment.

 Long story short, I injected a differential signal into the X_24_N and X_24_P with an amplitude of 800 mVpp and an offset of 500mV dc using a Rigol SDG2042X. I configured the Rigol outputs to have 180 degrees difference and connected the signal outputs to X_24_N and X_24_P (the order shouldn't matter). The device seems to be powering up just fine and producing a carrier with similar phase noise as when using an on-board xtal:

The device that I use to capture the pic on the left is different than the one on the right because I didn't want to hack into 2 just yet.

Using a single ended configuration seems to exhibit very high phase noise so I didn't use it.

In any case it looks like its possible to use an external (differential) oscillator to feed the CC13xx and possibly synchronize two of them. I will post an update once I am able to synchronize 2 CC13xx

I have just one question

1. What is the maximum voltage that wouldn't damage the IC at the X_24_N and X_24_P pins?