Crystal selection guide

[parth4]

PLEASE GUIDE US FOR SELECTION OF 8MHZ CRYSTAL FOR STM32L462CEU6 MCU.

[STTwo-32]

Hello @parth4 and welcome to the ST Community. 

I advise you to refer to this AN2867 Application note "Oscillator design guide for STM8AF/AL/S, STM32 MCUs and MPUs" and check the Table 6 and 7 for recommended crystal, that may help you on your needs.

Best Regards.

STTwo-32

[parth4]

THERE IS NO SPECIFICATION ABOUT 8MHZ CRYSTAL COMPONENT FOR STM32L4 SERIES , IN TABLE 7 THERE IS ONLY 32.768KHZ CRYSTAL ARE THERE BECAUSE IT IS LSE TABLE, SHARE THE PART NUMBER IF YOU CAN OTHERWISE GUIDE US FOR SELECTION PARAMETER LIKE CAPACITANCE LOAD, FREQUENCY TOLERANCE.

[STTwo-32]

Please have a look at the chapters 4 and 5. You should have a guide on how to select your oscilator for both LSE and HSE.

Best Regard.

STTwo-32

[parth4]

CAN YOU PLEASE GIVE ME VALUE OF LOAD CAPACITANCE OF 8 MHZ CRYSTAL FOR STM32L462CEU6 ?

[Tesla DeLorean]

Please avoid ALL CAPS

If you want to copy existing EVAL, NUCLEO, DISCO designs you can find schematics and BoM under the "CAD Resources" tabs on the product pages.

[STTwo-32]

Hello @parth4 

for more informations. Please have a look at the page 122 and the note on page 123 of the DS11913.

Best Regards.

STTwo-32

[tjaekel]

You have the option to use a real XTAL (crystal) or a CMOS OSC digital source.
The difference is just:

• a XTAL (crystal) needs a configuration on CLK _Config as XTAL (both pins used, in analog OSC mode)
• a CMOS OSC source needs a configuration in "bypass mode" (just one pin used, as digital OSC signal)

As long as the XTAL (or CMOS OSC)  frequency is within the valid range (check datasheet) - all fine and the CLK system config can be adjusted to your external CLK source.
Just check what is the min and max external frequency.

Best is:
check similar schematics for your MCU (for similar boards). You should see how to connect a XTAL (the tiny caps needed there, a digital CMOS OSC might be easier).
If you want to connect a CMOS OSC instead: it uses just one pin and the clock source has to be set to "bypass mode" (using just one pin CLK digital input signal).

[parth4]

selection of 8mhz crystal for sm32l462ceu6

as per datasheet C stray 10pf , and they have given this on page no 122 "For CL1 and CL2, it is recommended to use high-quality external ceramic capacitors in the 5 pF to 20 pF range (typ.)"

so we have assume load capacitance value 12.5pf , we got Cl1=Cl2= 5pf.

also ECS internation suggest "High Drive - The other extreme is more drive than the crystal and the oscillator loop can withstand. Some of the STM32 MCU’s have a HIGH DRIVE configurable setting, for these its recommended to use 12.5pF CL crystal."

so 8 mhz crystal with load capacitance value 12.5pf is right or wrong?

in reference board NUCLEO-L476RG  there is 16pf load capacitance value 8mhz crystal used , which one is right?

 

[Uwe Bonnes]

Writing in all capital letter is often understood as screaming at the readers. Consider communication in a normal voice...