why use TCXO, effect of not using TCXO for 32MHz?

[Aagra.11]

I have read different articles of STM and received different mails to use TCXO to give 32MHz clock. I could not find the reason and impact of it. In my application, it is outdoor and able to go temperature upto 85C temperature and using 22dB with 865MHz and its low power device.

My questions are:

1- If i use normal crystal of 10PPM (frequency tolerance and stability), what is the issue? what is the drift i can expect in clock and how it is going to impact the RF communication or any other place in MCU?

2- what is the PPM budget defined for STM32WL? (referred AN2867)

3- i have choosen below crystals, kindly confirm, which one can i use ?

ECS-320-8-37B-7KY-TR ECS Inc. | Crystals, Oscillators, Resonators | DigiKey

ECS-320-10-37B-CKY-TR ECS | Mouser India

ECS-320-8-36B-CKY-TR ECS | Mouser India

ECS-320-8-47B-7KY-TR ECS Inc. | Crystals, Oscillators, Resonators | DigiKey

4- if i have to use TCXO only, can i use below part as used part in nucleo board is not available?

TG2520SMN 32.0000M-ECGNNM3 Epson Timing | Mouser India

ATX-11-F-32.000MHz-F05-T ABRACON | Mouser India

else suggest the alternate part.

regards

Ankush Agrawal

[Tesla DeLorean]

The use of TCXO in radio applications is for the tight on-frequency transmission, it narrows the overall band which your radios occupy, and improves the receiver sensitivity as the transmitters are putting their energy where they are supposed too, and the receiver is looking in the right place.

[Aagra.11]

Thanks Tesla for quick reply. As I know, crystal work is just to give the clock pulses. accuracy of clock is going to define the things, which you said. so thats where my another question is, what the accuracy we are looking for?

as TCXO also come in different tolerance and frequency stability, what tolerance and stability should be choosen?

[Tesla DeLorean]

Semtech's TCXO recommendations look to be 0.5 ppm over temperature, 2.5 ppm overall

[Aagra.11]

What is the source of data?

as i refer the datasheet of stm32wl, it says OSC_ TRM = 30ppm and FERR_L = 50PPM, Ftol for crystal given is 10PPM for initial, temperature and aging.

[Aagra.11]

hi STM team

can you help to close this?

I am unable to select TCXO selection as :

1. Datasheet of STM32WL does not contain the value of gmcrit / gm for high speed crystal.
2. Datasheet of any TCXO does not have ESR values.
3. Part recommended in the STM32WL eval board, is not able to find on internet. 

also part given in reference design for 32.768KHz has given the calculated gmcrit value of 14.5uA/V while datasheet says 2.7uA/V. what should be done?