Linked Questions

8
votes
3answers
7k views

Crystal oscillator load capacitance, again

There's a lot of seemingly conflicting information regarding how the load capacitance for a parallel resonant crystal is calculated. Faced with a lot of problems in recent years with non-oscillation ...
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 ...
4
votes
4answers
1k views

Designing 64.5kHz Hartley Oscillator

I am taking an analogue electronics course and have been given an assignment to create a 64.5kHz Hartley oscillator using any 5V rail-to-rail operational amplifier. I am trying to design the circuit ...
2
votes
3answers
2k views

For a crystal oscillator circuit, what effect would a series resistor have on the inverter input?

In some application notes, there is a recommendation to use an external resistor in series with the OSC_OUT pin to reduce the power dissipated by the crystal, if necessary to do so. A good example is ...
5
votes
1answer
811 views

Crystal Oscillators in MCU

let's consider a MCU (for instance ATMEGA328) with a crystal. I know that the electrical model of a crystal is this one: My question is: which is the circuit that makes it oscillate? I do not see it ...
1
vote
3answers
2k views

why capacitors are used with crystal oscillator?

I want to learn 8051 programming so I begin from hardware in which crystal oscillator is connected with capacitors. can anyone please explain why capacitors are used and why those 22pF? how they ...
5
votes
1answer
843 views

Why are the capacitors necessary for a quartz crystal?

I read that it is recommended to connect 2 grounded capacitors to both ends of the quartz crystal. But that doesn't make any sense to me. Since capacitors have no resistance, wouldn't that make it so ...
2
votes
2answers
863 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 ...
5
votes
1answer
268 views

Voltage levels of Microcontroller Oscillator Pins

I am using MPC5606S Microcontroller. I want to clear one concept and have a doubt. The Microcontroller using 8MHz crystal on the pins 27 (XTAL) and 29 (EXTAL) And a 32.768kHz RTC crystal between ...
2
votes
2answers
547 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 ...
0
votes
2answers
421 views

Getting CL of XTAL

I'm using a dsPIC30F4011 in my project and I want to put a 6MHz XTAL between OSC1 and OSC2 pins. The circuitry goes like this: I want to know the values of C1 and C2 in the circuit, and I read ...
-1
votes
2answers
67 views

External oscilator on stm32f030

I am not sure if I calculated R_ext right. I am planning to use this oscilator. According to the document the calculation for R_ext is: ...
0
votes
4answers
85 views

How is the second capacitor charged in a Colpitts oscillator?

C1 is connected to ground, so there should be no current from C1 to C2. C2 will get charged by L1, but then in that case those two capacitors were not connected in series, they can't divide voltage, ...
0
votes
3answers
141 views

How are size of caps determined/calculated for use in smoothing voltage?

I'm reading this great book (AVR Programming: Learning to Write Software for Hardware by Elliot Williams) and setting up my arduino atmega328pu, usbasp programmer and using avrdude to program the chip....
0
votes
2answers
109 views

RTC time advancing

I'm working in some projects with an RTC. I'm using the PCF85063A. The problem is: the RTC counter is advancing from real time about 2 minutes per week. I searched for hardware and firmware errors, ...

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