Types of crystal

[FreshmanNewbie]

This question is asked to understand the difference between "Full Swing crystal" and what it the low power crystal?

Can someone tell me what is the basic difference and how will it impact in simple terms?

--- Updated Feb 22, 2024 ---

This question is asked to understand the difference between "Full Swing crystal" and what it the low power crystal?

Can someone tell me what is the basic difference and how will it impact in simple terms?

My question is based on this article:

Atmel Removes Full-Swing Crystal Oscillator

It is one of our favorite chips, and the brains behind the Arduino UNO and its clones, and it’s getting a tweak (PDF). The ATmega328 and other megaX8-series chips have undergone a subtle desi…

hackaday.com

Can someone explain the article in simple terms about its impact?

 

[danadakk]

Low power osc considerations :

ATmega48/V / 88/V / 168/V

atmel-studio-doc.s3-website-us-east-1.amazonaws.com

This - https://www.omzlo.com/articles/using-an-external-crystal-on-the-atmega328pb

Seems like there is no official reason given by Atmel.....

But various threads - cant run at 20 Mhz.....Excess xtal power dissipation.....


Regards, Dana.

 

[FreshmanNewbie]

Low power osc considerations :

ATmega48/V / 88/V / 168/V

atmel-studio-doc.s3-website-us-east-1.amazonaws.com

This - https://www.omzlo.com/articles/using-an-external-crystal-on-the-atmega328pb

Seems like there is no official reason given by Atmel.....

But various threads - cant run at 20 Mhz.....Excess xtal power dissipation.....


Regards, Dana.

Can you tell me what has changed in simple terms and how wil it impact?

 

[danadakk]

I do not know details. A good contact would be to contact a Microchip FAE, or the manufacturers
rep, or a Microchip forum to see if you can get the detailed answer. Unless of course another aid
here has some insight.


Regards, Dana.

 

[D.A.(Tony)Stewart]

Can you tell me what has changed in simple terms and how wil it impact?

The external Oscillator pins on Atmel's chips in 2018 changed to exclude full-swing ext. Osc. is what i read.
My guess is they use an LDO at Vdd min like 1.8 to 2.0V to run the inverter gates only used for high speed external oscillator at Vdd minimum then use a sub-threshold level to internally clock at Vdd.

Here are specs for a 74AHCT' level shifter where the CMOS family letters mean, I believe
A means advanced low impedance (3.6V type <25 ohm vs 74HC 5.5V 50 ohms)
H means high voltage
C means complementary
T for TTL compatible input threshold.

Anyone else want to guess this proprietary info?

 

[FvM]

"Full swing crystal" involves a misunderstanding. It's about "full swing crystal oscillator". Different oscillator circuits rather than crystal types.

According to my knowledge, the main impact of reduced oscillator swing is reduction of EMI. Reduced ower consumption is a wanted side effect.

 

[D.A.(Tony)Stewart]

Some PCB designers prefer no ground plane under Xtal Osc to reduce shunt capacitance but this makes the two cap & resonator loop a source of emissions with V^2 power spectrum reduction on all the odd harmonics of xx MHz Xtal , but a ground plane reduces emissions so reduce shunt caps by trace C. (1~2 pF?)

But you are always safer to use an active oscillator chip or XO at the reduced swing spec on input.

just found

"Furthermore, in the latest technology and also in order to reduce the
consumption, the oscillation level is restricted to within the range of 1V, again
increasing the susceptibility"

https://ww1.microchip.com/downloads/en/Appnotes/Atmel-8128-Best-Practices-for-the-PCB-Layout-of-Oscillators_ApplicationNote_AVR186.pdf