Internal 48MHZ RC Enough for Radio Application?

[User16438042334827474767]

I am designing an Outdoor Radio product with STM32WLE5CBU6. my question is whether the Internal RC Oscillator is enough for my radio applications ? or do I need to add External TCXO in my circuit considering the outdoor temperature environment? for my product cost-cutting. please suggest.

[Andrew Neil]

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@User16438042334827474767 wrote:

my question is whether the Internal RC Oscillator is enough for my radio applications ? 

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Impossible to say without details of what these "radio applications" are.

You can find the specifications of the Internal RC Oscillator in the datasheet - work out from there whether that meets your requirements.

[AScha.3]

No.

Usually you want/need for GHz or many-MHz PLL a very stable clock source, typical a crystal.

See basic:

HSE32 is the "standard" clock for the PLL. (If 20 ct for a crystal is too much, you have another problem...)

[User16438042334827474767]

Application LORA 868MHZ P2P Weather station.not LORAWAN.

[Andrew Neil]

Again, look at the specs in the datasheet - do they fit with your application requirements?

Local regulations will put requirements on frequency stability/accuracy ...

[AScha.3]

Ok, but you still want receive it - right ? 🙂

So:

The fequency should be, where you set it to - lets say- 0.01 MHz, 10kHz tolerance , to get it working at a channel bandwidth of 125 kHz.

THIS alone gives about 11 ppm max. tolerance, so even should be a +/- 10ppm crystal, not the cheapest 50ppm thing. And about the RC "reference" ...

... 10 000 ppm away .... you wouldnt even know, on which channel you sending.  🙂

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[TDK · Accepted solution]

It needs an external crystal to have wireless transmission capability.

[Andrew Neil]

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@User16438042334827474767 wrote:

 for my product cost-cutting. please suggest.

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If you really want to cut costs, do you really need to use LoRa?

You pay a premium (to Semtech) for that ...

[User16438042334827474767]

Okay.