Precautions when purchasing crystals

1, 32.768KHz crystal is the most widely used frequency, we need to master the crystal precision, crystal model: If the model is a patch crystal, you do not need to ask the foot, and can see from the model the size of the crystal, crystal belongs to Which package. Just master the crystal's load and accuracy on it. Plug-in crystal oscillator is also the case, the plug-in crystal oscillator does not know the model, you need to specifically describe the shape of the plug-in crystal, the common plug-in crystal shape has a cylinder, the common size of φ3 * 8mm φ2 * 6mm φ1 * 5mm these three.

2, for the MHZ crystal, we need to clearly know the crystal model (or volume). If we only know the volume, we also need to know the pin of the crystal oscillator. The commonly used SMD crystal oscillator has 2 pins and 4 pins. It is also necessary to know the load (PF) and accuracy (PPM) of the crystal oscillator. Other requirements that have special requirements also need to be listed. For example, the resistance value C1 CL DL, etc., need to be customized at the time of production.

3, for the market's commonly used SMD package: SMD2016 2520,3225,5032,6035,7050. The above package, in the case of knowing the frequency, if the crystal is a two-pin chip crystal, we need to know whether it is a ceramic surface package or a metal surface package. Two-pin SMD ceramic surface package commonly used specifications are 5032 SMD crystal, 6035 SMD crystal, if the crystal is a four-pin SMD crystal, we must pay special attention, because the four-pin SMD may be a passive crystal oscillator It may be an active crystal oscillator, which distinguishes between the active and passive crystals. From voltage or accuracy. Of course, the accuracy is not completely accurate. If the 5PPM crystal oscillator may also be an active crystal oscillator or a passive crystal oscillator, the accuracy below 5PPM, such as 2PPM, 1PPM, and 5PPM, must be an active crystal oscillator. The voltage must be accurate. A quartz crystal with a voltage must be an active crystal. A quartz crystal without a voltage must be a passive crystal. The active crystal oscillator is further divided into a temperature compensated oscillator, a voltage controlled oscillator, and a pressure-controlled temperature compensated oscillator.

4, for the active crystal, how to get from the model can be whether the temperature compensation crystal, or voltage controlled crystal. TCXO is an abbreviation of Temperature Compensating Oscillator. VCXO is an abbreviation of Voltage Controlled Oscillator. VC-TCXO is an abbreviation of Voltage Controlled Temperature Compensating Oscillator. The imported crystal oscillator is a wide variety of KDS crystal oscillators in the field of crystal components. In addition to passive crystal oscillators and active crystal oscillators, KDS also performs crystal filters. In the KDS crystal oscillator, all models that begin with DSB are temperature compensated oscillators. The models that begin with DSV are voltage-controlled oscillators. The models at the beginning of DSO are ordinary active crystal oscillators. The models at the beginning of DSA are all voltage-controlled temperature-compensated oscillators. Device. How to know the volume from the model. ; To judge the volume from the model, you don't need to look at the letters in front of it; you only need to study the following numbers. For example, the DSV221SV; DSV models at the beginning are all voltage-controlled oscillators. The following number 221 corresponds to our 2520 SMD package, so the volume of its VCO is 2.5*2.0mm. Another example is the DSB321SC. The DSB starts with a temperature compensated oscillator. The number behind it corresponds to our 3225 SMD package, so the volume of its temperature-compensated oscillator is 3.2*2.5mm. Therefore, all the parameters of the crystal oscillator can be known from the model, and only the crystal oscillator load capacitance, PPM, is required. Voltage can be the size.

The above is the most popular and practical method of crystal selection, hoping to help those in need.