solution to the 32.768kHz crystal oscillator cannot oscillate
The use of crystal oscillators is very common, and crystal oscillators exist in almost all digital circuits. In daily use, the crystal oscillator may fail to oscillate. In order to help everyone deeply understand the reason why the crystal oscillator cannot oscillate, the Chinese PCBA manufacturer - SysPCB will explain the reason why the crystal oscillator cannot oscillate and its solutions in conjunction with the 32768 crystal oscillator.
First, causes of no oscillate
It is a common phenomenon that the crystal oscillator of a single-chip microcomputer can not oscillate, so what are the reasons that cause the crystal oscillator to fail to oscillate?
(1) PCB board wiring error;
(2) There is a problem with the quality of the microcontroller;
(3) There is a problem with the quality of the crystal oscillator;
(4) The load capacitance or matching capacitance does not match the crystal oscillator or the capacitance quality is problematic;
(5) The PCB board is damp, causing impedance mismatch and unable to start oscillate;
(6) The trace of the crystal oscillator circuit is too long;
(7) There is a trace between the two feet of the crystal oscillator;
(8) The influence of peripheral circuits
Second, no oscillate solution
It is recommended to troubleshoot one by one as follows:
(1) Eliminate the possibility of circuit errors, so you can compare with the recommended circuit of the corresponding model microcontroller.
(2) Eliminate the possibility of poor peripheral components, because peripheral components are nothing more than resistors and capacitors, so you can easily identify whether they are good products.
(3) Eliminate the possibility that the crystal oscillator is a stop oscillate product, because you will not only try one or two crystal oscillators.
(4) Try to change the capacitors at both ends of the crystal, maybe the crystal can start to oscillate. For the size of the capacitor, please refer to the instructions for use of the crystal.
(5) During PCB wiring, the trace of the crystal oscillator circuit should be as short as possible and close to the IC as much as possible to avoid routing between the two pins of the crystal oscillator.
Third, the ultimate solution to the 32.768kHz crystal oscillator cannot oscillate
The 32.768kHz crystal oscillator is the most widely used crystal oscillator on the market. EPSON currently provides three types of 32.768kHz crystal oscillator products to meet the different needs of customers, namely: 32.768kHz active crystal (OSC), 32.768kHz passive crystal (X'tal) and real-time clock module with built-in 32.768kHz crystal resonator (RTC).
The OSC and RTC have built-in corresponding circuits, so they are not prone to no-oscillate problems. There is no need to consider the relatively complicated frequency matching problem in actual use.
The failure to oscillate mainly occurs in passive crystal oscillators, especially the passive crystal oscillators (X’tal) of the kHz level, while the MHz level AT crystal oscillators are relatively rare.
Fourth, what is the reason why the crystal oscillator cannot vibrate?
The answer is: the circuit structure does not match the crystal unit. This leads to problems such as insufficient frequency stability, stop-oscillate, or unstable oscillation. Therefore, in the circuit design, in order to obtain a stable oscillation, the matching of the quartz crystal unit and the oscillation circuit is usually very important.
To solve the problem that the crystal oscillator cannot oscillate, at least the following three items must be evaluated: oscillation frequency (frequency matching), oscillation margin (negative impedance) and excitation power.
Why does the crystal oscillator work well in the small batch trial production, but the defect rate appears in large numbers during the mass production?
The answer also is that the circuit structure does not match the crystal unit. Due to the probability problem, it was not discovered in time due to the small quantity during the trial production of small batches.
Fifth, how to avoid the time delay and high defect rate caused by the failure of the crystal oscillator?
1. Choose a reliable brand and purchase channel
There is no doubt that the consistency and stability of the crystal oscillator itself is one of the keys to solving the problem of inability to vibrate. If the stability and consistency of the crystal oscillator itself is not good, the matching of the circuit structure and it will be impossible.
After the brand is determined, the purchase channel is also crucial. Good and bad in the market, it is recommended to place an order directly from the brand manufacturer or the first-level authorized agency of the brand.
2. Choose an active crystal as much as possible
There is no doubt that the price of active crystal oscillators is more expensive than passive crystals, but since the original factory has already configured the internal circuit, there is basically no circuit matching problem, which greatly avoids the problem of crystal oscillator failure.
3. If your crystal oscillator is used on an RTC chip, it is strongly recommended that you replace the existing RTC with the real-time clock module provided by Epson.
Due to the built-in 32.768kHz crystal, on the one hand, it can save user design space, and at the same time avoid the problem of crystal oscillator not vibrating caused by unreasonable external crystal circuit matching design, greatly simplifying the design, and more importantly improving product reliability and production efficiency.
The above is the relevant content of "crystal oscillator". We believe everyone has a certain understanding of the reasons and solutions for the 32768 crystal oscillator not able to oscillate.