Does BlueNRG support TCXO on FXTAL and LSCO on SXTAL ?

[bboulet]

Hello,

I want to add a BlueNRG in my design and I would like to use the TCXO used on the processor (STM32L451) and connect it on FXTAL, is possible possible ? if yes on which pin ? FXTAL0 or FXTAL 1 ?

I would like to do the same thing with the 32.768KHz, and use the LSCO from the STM32 to the blueNRG, is possible possible ? if yes on which pin ? SXTAL0 or SXTAL 1 ?

regards,

Benjamin

[Winfred LU]

Hi Benjamin,

The answer is Yes and Yes.

For TCXO, the correct pin is the FXTAL0 to apply the TCXO signal.

For STM32 LSCO, the correct pin is XSTAL0 to provide the 32 kHz signal.

You have to provide a sinusoidal signal without DC as input, with the maximum level of 1.2V.

It is because at the input there is a DC block and after that a square circuit, so no square signal is necessary.

But the question would be why do you want to use an external TCXO?

BlueNRG series IC's requirement about frequency drift is relaxed. A TCXO is not necessary for the application.

Considering the higher price for a TCXO, usually it is not the final choice.

Best Regards,

Winfred

[bboulet]

Hello Winfred,

thank you for your answer !

I already use a TCXO on other ICs (because one of them need to have one) on my board, the idea is to use the same clock on every chip in order to reduce the cost of the BoM as well as the place on the PCB.

regards,

Benjamin

[Winfred LU]

Hi Benjamin,

Well understand.

Since TCXOs have better performance, in your case the BoM cost is also better, it will be perfect to proceed.

Best Regards,

Winfred