Glossary - alphabet order - "P"


Abbreviation for Positive Emitter Coupled Logic. This is an I/O level in LSI ICs.

LV-PECL output definition ECL output definition Output voltage level cpmparison


Abbreviation for Phase Locked Loop. This is a circuit or IC that can create any output frequency based on a clock signal having a specified frequency. Recently, these are used with variable reception frequency circuits in TV and radios. Seiko Epson has developed and marketed programmable oscillators that include PLLs.

Block diagram of PLL circuit

Reference: SG-8000 Series , PLL Oscillator

PLL oscillator

This is a crystal oscillator that includes a PLL circuit. PLL oscillators have the advantage that only one type of fixed frequency internal crystal need be prepared, and that a much shorter manufacturing lead time can be achieved. It can also output at over 100 MHz, which is difficult with an ordinary overtone crystal oscillator. PLL oscillators are divided into two types based on the number of outputs: the single-frequency output type and the multiple-frequency output type. Epson 's single-frequency output products are found in the SG-8000 Series.

Reference: PLL , SG-8000 Series

PROM writer

PROM writer (for SG-8002 Series)

The PROM writer is a programming tool used for programmable crystal oscillators. It is called a PROM writer because it writes frequency data to the internal PROM of programmable crystal oscillators. This is a tool only prepared for use with SG-8000 series. PROM Writer is Seiko Epson's registered name.

Reference: SG-Writer , Programmable crystal oscillator


A package is a container, such as for a crystal chip, or for crystal chip and IC chip. The package's functions include facilitating board mounting of devices and maintaining an internal vacuum or inert gas in order to optimize the internal crystal's oscillation characteristics. As such, packages are classified by their materials as metal, plastic, or ceramic packages, and are also classified by their pin shapes as through-hole type or SMD (surface mounted device) type packages.

Parallel interface

A parallel interface provides a connection method whereby multiple units of data can be combined into multi-bit signals and are transferred between devices through multiple data lines. The censorings parallel interface used for printer ports in computers is a leading example of a parallel interface.

Reference: Serial interface

Parallel polarized light

P -polarized light is linearly polarized light that runs in a plane formed by the axis of light propagation and the line normal to a sample surface. S- polarized light is linearly polarized light that runs perpendicularly to this plane. In the case of a cubic prism comprising two triangular prisms, the line normal to a sample surface is the line normal to coated surfaces of these two triangular prisms that are opposed and attached each other.

Pb free product

Reflow profile ofPb free products

Pb free products are products that all lead has been eliminated from its components and surface-treatment materials. However, Pb free products require a higher soldering temperature than Pb soldered products when mounted.

Reference: Working for EU RoHS/Pb FREE , Reflow profile

Period jitter

A type of jitter defined in specification. See "jitter".

Reference: Jitter

Phase difference

It is expressed by an angle unit and yielded due to the light path difference (waveform offset) among oscillating components of a light beam, which are perpendicular each other. (This is generally viewed as the offset between the peak and valley of the waveform. Each wavelength is 360°).

Phase noise

This refers to useless energy that is radiated near the oscillation frequency, and that occurs due to the internal and external environmental factors (noise) of a crystal oscillation circuit. Wireless signal transmission errors can occur when this noise value is too high.

Photolithography processing

This type of processing uses chemicals to dissolve a crystal plate or metal layer, usually in order to make a tuning fork crystal shape for a tuning fork crystal chip, or to create electrodes. Before this processing approach was developed, mechanical processing was used, but photolithography processing offers the following advantages.

  1. This is the same process as is used to fabricate ICs with high dimensional accuracy, so crystal chips can be made very small and very precise, etc.
  2. Chemical processing enables several hundred tuning fork crystal chips to be made from a single crystal plate, with consistent quality and at low cost.
  3. Since no strain remains in a crystal chip, the resulting crystal chip provides a stable oscillation frequency for a long time.

Reference: Leaf type crystal chip , mechanical processing

Piezo-electric effect

The piezo-electric effect is the electric charge that is generated in a particular axial direction when pressure is applied in a particular crystal axial direction against a typical crystalline material (such as quartz crystal). By contrast, the mechanical stress that occurs when a charge is applied in the same axial direction is called a reverse piezo-electric effect. Materials that have these properties include monocrystalline materials such as quartz crystal (SiO2), lithium tantalum trioxide (LiTaO3), and lithium niobium trioxide (LiNbO3), as well as polycrystalline (piezo-ceramic) materials such as barium titanium trioxide (BaTiO3). Each of these materials has its advantages and disadvantages, and quartz crystal is best for stable oscillation.

Piezo-electric effect Reverse piezo-electric effect

Reference: Piezo-electric element

Piezo-electric element

This refers to any crystal element that has a piezo-electric effect. These crystal elements include monocrystalline elements such as quartz crystal (SiO2), lithium tantalum trioxide (LiTaO3), and lithium niobium trioxide (LiNbO3) elements, as well as polycrystalline ceramic elements.

Reference: Piezo-electric effect

Plastic package

This is a package whose body is constructed of a mold plastic material. A hermetically sealed package (made of metal, etc.) with a vacuum interior is needed to preserve the characteristics of a crystal unit. Consequently, conventional crystal unit package have appeared different from those used for other electronic devices including ICs. For these reasons, crystal unit have required special handling (regarding temperature, impact, etc.) when being mounted on a circuit board. Recent plastic package crystal devices can be handled the same as ICs, and are especially effective when used with a hybrid product that integrates a crystal unit with an IC.

Plastic package(Epsontoyocom SG-615) Plastic package Perspective drawing

Reference: Ceramic package , Metal can package

Polarized beam splitter

It is a prism that separates an incident light beam into two beams of which polarized components (P and S components) are orthogonal each other.

Polarized light

It generally means light of which wave-oscillating has regular directions. It is classified into three categories; linear polarized, circularly-polarized and elliptically-polarized light, if a parallel component of light is defined as a change in the X axis and a perpendicular component as a change in the Y axis. The linear polarized light has the phase difference: 0° (or 0°+N × 360°, N is an integer ) and follows a linear track. The circularly-polarized light has the phase difference: 90° ( or 90°+N × 360°) and follows a circular track. The elliptically-polarized light has the phase difference in between the above two light. Separated parallel and perpendicular components in each of the above polarized light are the linear polarized light oscillating within a plane.


This refers to the polishing of crystal plate surfaces. This includes both lapping (with a fine-grained abrasive) and polishing (with a polishing cloth dipped in a polishing substance). These types of surface processing are important for obtaining the desired frequency and to improve the vibration efficiency. In particular, surface accuracy has a very large effect on the characteristics of AT crystal units. Finer surface accuracy is required for higher frequencies.

Programmable crystal oscillator

This indicates the crystal oscillators that include a PLL circuit and can be programmed to output a desired frequency. Being able to program for any output frequency facilitates short-lead-time, small-lot production. A special programming tool is necessary to write frequency data to blank crystal oscillators. Epson's programmable crystal oscillators are the SG-8000 Series, and are programmed by the SG-Writer programming tool.

Programable crystal oscillator (Epsontoyocom SG-8002) Programming tool (Epsontoyocom SG-Writer)

Reference: SG-8000 Series , SG-Writer

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