Linked Questions

8
votes
3answers
1k views

Why do MCU crystal oscillators not fry the crystals?

I am trying to better understand crystal oscillators. I have been reading ST's AN2867, where they explain that, depending on the crystal, a series resistor (R2 in the diagram below) on the output side ...
2
votes
2answers
835 views

Crystal's datasheet give load capacitance is 20pF, do I need external load capacitors?

I use external crystal for HSE of STM32F0. I plan to use 8MHz Cylinder Crystals. Datasheet of this crystal below Datasheet give crystal load capacitance is 20pF My questions: 1/ Do I need to add 2 ...
0
votes
3answers
317 views

What is the purpose of capacitors parallel to crystal? [duplicate]

In many schematics, we have two capacitors connected in parallel to a crystal? Why do we have capacitors parallel to crystal? Whats the purpose? How are the capacitor values determined ?
5
votes
3answers
1k views

What actually is the load capacitance of a quartz crystal?

I'm having hard time understanding the principles of piezoelectric crystal oscillators. I've found this picture: I understand that "load capacitance" is something you have to connect to a crystal. I ...
8
votes
4answers
3k views

Different (15 and 10 pF) load capacitors on 32.768 Hz quartz crystal

I've got some random chinese electronic desktop clock/alarm. It turned out that it's completely missing any capacitors on crystal. That was the reason why the clock were going faster ~5 min each month....
2
votes
2answers
544 views

Crystal oscillator on custom ATMega2560 board is at the wrong frequency

I have designed a custom board using an ATMega2560. The board works fine when configured to use the internal oscillator. The board stops working when I configure it to use the the external 16MHz ...
2
votes
3answers
2k views

Capacitive load - Matching Right Crystal and Caps for oscillator circuit - DS1302 RTC - cut and trim

CL = (C1 * C2) / (C1 + C2) + Cstray I have a 12.5pf crystal. DS1302 is happy with 6pf. what is trim capacitors to make him happy using 12.5pf? 12.5-6=6.5pf (6.5*6.5) / (6.5+6.5) + cstray= 3.25pf + ...
1
vote
4answers
2k views

Resistor symbol in a schematic with zero value

I can't figure out the purpose of the 0Ohm resistor in bellow schematic. It's crystal oscillator configuration and why the designer have included a resistor there with 0ohms ? Any idea ?
1
vote
2answers
845 views

What is the influence of an asymetric load capacitance on a crystal duty cycle

I have a crystal oscillating at 25MHz (datasheet). The recommanded load capacitance is 18pF according to the datasheet. The crystal is connected to a component where the capacitance on the pin are ...
1
vote
1answer
501 views

How do I deal with different XTAL pin capacitance when selecting XTAL and load capacitors

I'm trying to select a 32kHz crystal and appropriate load capacitors for Atmega48A MCU. Atmega48A specifies different capacitances for Xtal1 and Xtal2 pins: 18pF for Xtal1 8pF for Xtal2 The ...