Crystal oscillator

Abstract

A crystal oscillator is configured by accommodating a crystal blank that functions as a crystal unit and an IC chip that includes at least an oscillator circuit using the crystal blank into a container in an integrated manner. In the IC chip, the oscillator circuit is connected to the crystal unit via a pair of crystal connecting terminals, an output from the oscillator circuit is supplied to a plurality of output buffers. In relation to the crystal connecting terminal having a phase opposite to that of an output from the on/off controllable output buffer, an output terminal of this output buffer is disposed farther than an output terminal of the output buffer that is not subjected to the on/off control.

What is claimed is: 
     
         1 . A crystal oscillator, comprising: a crystal unit; and an IC chip that integrates at least an oscillator circuit using said crystal unit, said crystal unit and said oscillator circuit being housed in a container,
 wherein said IC chip includes: a plurality of output buffers that amplify an output from said oscillator circuit and output the amplified output to outside; a pair of crystal connecting terminals that are used for electrical connection between said oscillator circuit and said crystal unit; and output terminals provided for said respective output buffers,   signals of an oscillation frequency component appear at said pair of crystal connecting terminals with phases opposite to each other,   each of said plurality of output buffers independently includes an inverting or non-inverting amplifier,   at least one of said plurality of output buffers is an output buffer whose output is on/off controllable according to an enable signal, and   said IC chip is configured such that, for each on/off controllable output buffer, in relation to said crystal connecting terminal having a phase opposite to that of the output of said each on/off controllable output buffer, an output terminal of said each on/off controllable output buffer is disposed farther than an output terminal of the other output buffer.   
     
     
         2 . The crystal oscillator according to  claim 1 , wherein the number of said output buffers is two. 
     
     
         3 . The crystal oscillator according to  claim 2 , wherein said oscillator circuit includes an amplifier of an inverting type, an input terminal and an output terminal of the amplifier of said oscillator circuit are connected with said pair of crystal connecting terminals, respectively, and only one of said output buffers is on/off controllable output buffer. 
     
     
         4 . The crystal oscillator according to  claim 2 ,
 wherein said oscillator circuit includes an amplifier of an inverting type,   said pair of crystal connecting terminals include: a first crystal connecting terminal connected to an input terminal of the amplifier of said oscillator circuit and a second crystal connecting terminal connected to an output terminal of the amplifier of said oscillator circuit,   a first output buffer of said two output buffers is an output buffer that includes the non-inverting amplifier and is on/off controllable, a second output buffer is an output buffer that includes the inverting amplifier and is on/off controllable, and   an output terminal of said first output buffer is disposed farther than an output terminal of said second output buffer in relation to said first crystal connecting terminal, and the output terminal of said second output buffer is disposed farther than the output terminal of said first output buffer in relation to said second crystal connecting terminal.   
     
     
         5 . The crystal oscillator according to  claim 1 , wherein the on/off control is performed by controlling a power supply of said on/off controllable output buffer according to the enable signal. 
     
     
         6 . The crystal oscillator according to  claim 1 , said on/off controllable output buffer includes an analog switch controlled by the enable signal and performs the on/off control by the analog switch. 
     
     
         7 . A crystal oscillator, comprising:
 a crystal unit; and   an IC chip that integrates at least an oscillator circuit using said crystal unit, said crystal unit and said oscillator circuit being housed in a container,   wherein said IC chip includes:
 two output buffers comprising a first output buffer and a second output buffer that amplify an output from said oscillator circuit and output the amplified output to outside; 
   a first crystal connecting terminal and a second crystal connecting terminal that are used for electrical connection between said oscillator circuit and said crystal unit;   a first output terminal and a second output terminal that are provided for said first output buffer and said second output buffer, respectively; and an enable terminal to which an enable signal is applied,   each of said first output buffer and said second output buffer independently includes an inverting or non-inverting amplifier,   signals of an oscillation frequency component appear at said first crystal connecting terminal and said second crystal connecting terminal with phases opposite to each other, a phase at an output of said second output buffer being opposite to a phase at said second crystal connecting terminal,   said second output buffer is an output buffer whose output is on/off controllable according to an enable signal, and   said IC chip is configured such that a distance from said second crystal connecting terminal to said second output terminal is larger than a distance from said second crystal connecting terminal to said first output terminal.   
     
     
         8 . The crystal oscillator according to  claim 7 , wherein said first crystal connecting terminal, said second crystal connecting terminal, said first output terminal and said second output terminal are provided on a surface of a semiconductor substrate which constitutes said IC chip. 
     
     
         9 . The crystal oscillator according to  claim 8 , wherein a first distance from said first output terminal to a terminal which is farther one of said first crystal connecting terminal and said second crystal connecting terminal from said first output terminal is larger than a second distance from said second output terminal to a terminal which is nearer one of said first crystal connecting terminal and said second crystal connecting terminal from said second output terminal. 
     
     
         10 . The crystal oscillator according to  claim 9 , further comprising a ground IC terminal for grounding said IC chip, said ground IC terminal being provided on said surface of said semiconductor substrate,
 wherein said ground le terminal is arranged at a position between said terminal which is said nearer one and said second output terminal.