On-die termination circuit and driving method thereof

Abstract

An on-die termination circuit is capable of increasing a resolution without enlargement of a chip or a layout size. The on-die termination circuit includes a control means, a termination resistance supply means, a code signal generating means. The control means sequentially generates a plurality of control signals in a response to a driving signal. The termination resistance supply means supplies a termination resistance in response to a coarse code signal having a plurality of bits and a fine code signal having a plurality of bits. The code signal generating means controls the fine code signal and the coarse code signal in response to the plurality of the control signals in order that the termination resistance has a level which is correspondent to an input resistance.

What is claimed is: 
     
       1. An on-die termination circuit comprising:
 a driving control means for sequentially generating a plurality of control signals in response to a driving signal; 
 a first termination resistance supply means for supplying a termination pull-up resistance in response to a first coarse code signal having a plurality of bits and a first fine code signal having a plurality of bits; 
 a first code signal generating means for controlling the first coarse and fine code signals in response to the plurality of the control signals so that the termination pull-up resistance has a level which corresponds to an input resistance; 
 a second termination resistance supply means for supplying a termination pull-down resistance in response to a second coarse code signal having a plurality of bits and a second fine code signal having a plurality of bits; and 
 a second code signal generating means for controlling the second coarse and fine code signals in response to the plurality of control signals so that the termination pull-down resistance has a level which corresponds to the termination pull-up resistance, 
 wherein the second code signal generating means includes: 
 a first resistance feedback unit for receiving the first and second fine code signals and the first and second coarse code signals and for outputting a feedback pull-down resistance; 
 a first coarse code generating unit for producing the second coarse code signal in order that the feedback pull-down resistance has a level corresponding to a reference resistance; and 
 a first fine code generating unit for producing the second fine code signal in order that the feedback pull-down resistance has a level corresponding to the reference resistance while the first coarse code signal generating unit is inactivated, and 
 wherein the first coarse code generating unit includes: 
 a level detecting unit for outputting a pull-down detecting signal by detecting a level of the feedback pull-down resistance based on the reference resistance in response to a first control signal; 
 an amplifier for amplifying the pull-down detecting signal in response to a second control signal and for outputting the amplified signal as a pull-down level signal; 
 a first register control unit for activating a first pull-down driving signal in response to the first control signal and for producing a second pull-down driving signal when the pull-down level signal goes from a first logic level to a second logic level; and 
 a first coarse register for generating the second coarse code signal based on a logic level of the pull-down level signal in response to a third control signal and the first pull-down driving signal. 
 
     
     
       2. The on-die termination circuit of  claim 1 , wherein the first resistance feedback unit includes:
 a first resistance unit for supplying a first feedback resistance corresponding to the first coarse code signal; 
 a second resistance unit for supplying a second feedback resistance corresponding to the first fine code signal; 
 a third resistance unit for a third feedback resistance corresponding to the second coarse code signal; and 
 a fourth resistance unit for supplying a fourth feedback resistance corresponding to the second fine code signal, wherein the first resistance feedback unit supplies the feedback pull-down resistance by connecting in series the first and second resistance units between a first supply voltage and an output node and the third and fourth resistance units between a second supply voltage and the output node. 
 
     
     
       3. The on-die termination circuit of  claim 2 , wherein a minimum variation of the first and third feedback resistance is larger than that of the second and fourth feedback resistance. 
     
     
       4. The on-die termination circuit of  claim 3 , wherein the second and fourth resistance unit includes first to fifth MOS transistors each of which has a gate to receive an input signal and are in parallel connected to each other. 
     
     
       5. The on-die termination circuit of  claim 4 , wherein the first and third resistance unit includes:
 sixth to ninth MOS transistors each of which receives an input signal through a gate, being connected to each other; and 
 first to fourth passive resistors which are connected to sixth to ninth MOS transistors, respectively. 
 
     
     
       6. The on-die termination circuit of  claim 1 , wherein the fine code generating unit includes a first fine register for generating the second fine code signal based on a logic level of the pull-down level signal and in response to the third control signal and the first pull-down driving signal. 
     
     
       7. The on-die termination circuit of  claim 6 , wherein the first code signal generating means includes:
 a second resistance feedback unit for receiving the first fine and coarse code signals based on the input resistance and for outputting a feedback pull-up resistance; 
 a second coarse code generating unit for producing the first coarse code signal in order that the feedback pull-up resistance has a level corresponding to the reference resistance; and 
 a second fine code generating unit for producing the first fine code signal in order that the feedback pull-up resistance has a level corresponding to the reference resistance while the second coarse code signal generating unit is inactivated. 
 
     
     
       8. The on-die termination circuit of  claim 7 , wherein the second resistance feedback unit includes:
 a first pull-up feedback resistance unit for supplying a first code resistance corresponding to the first coarse code signal; and 
 a second pull-up feedback resistance unit for supplying a second code resistance corresponding to the first fine code signal, wherein the second resistance feedback unit supplies the feedback pull-up resistance by connecting in series the first and second pull-up feedback resistance units. 
 
     
     
       9. The on-die termination circuit of  claim 8 , wherein a minimum variation of the first code resistance is larger than that of the second code resistance. 
     
     
       10. A method of providing on-die termination, comprising:
 providing a first termination resistance based on a first coarse code signal of a plurality of bits and a first fine code signal of a plurality of bits received from a first code signal generating unit, including:
 controlling the first termination resistance using the first coarse code signal; 
 in response to a comparison between the first termination resistance and a first predetermined resistance, controlling the first termination resistance using the first fine code signal; 
   providing a second termination resistance in response to a feedback signal from the first code signal generating unit based on a second coarse code signal and a second fine code signal received from a second code signal generating unit, including:
 controlling the second termination resistance using the second coarse code signal; and 
 in response to a comparison between the second termination resistance and a second predetermined resistance, control the second termination resistance using the second fine code signal.  
   
     
     
       11. The method of claim 10, wherein:
 the first termination resistance is a termination pull-up resistance; and   the second termination resistance is a termination pull-down resistance.    
     
     
       12. The method of claim 11, wherein:
 the first predetermined resistance is a reference resistance.    
     
     
       13. The method of claim 12, wherein:
 the comparison between the termination pull-up resistance and the first predetermined resistance is a level comparison.    
     
     
       14. The method of claim 10, wherein:
 the feedback signal is based on the first coarse code signal and the first fine code signal.    
     
     
       15. The method of claim 14, wherein:
 the comparison between the termination pull-down resistance and the second predetermined resistance is a level comparison.    
     
     
       16. An on-die termination circuit, comprising:
 a first termination resistance supply unit connected to a first coarse code signal and a first fine code signal, for producing a first termination resistance;   a first code signal generation control unit including a first comparator, the first code signal generation control unit being connected to the first coarse code signal, the first fine code signal, and a reference resistance, for producing a first control signal;   at least one first register connected to the first control signal for producing the first coarse code signal and the first fine code signal;   a second termination resistance supply unit connected to a second coarse code signal and a second fine code signal, for producing a second termination resistance;   a second code signal generation control unit including a second comparator, the second code signal generation control unit being connected to the first coarse code signal, the first fine code signal, the second coarse code signal, the second fine code signal, and the reference resistance, for producing a second control signal; and   at least one second register connected to the second control signal for producing the second coarse code signal and the second fine code signal;   wherein the second code signal generation control unit includes:
 a first resistance feedback unit for receiving the first and second fine code signals and the first and second coarse code signals and for outputting a feedback pull-down resistance; 
 a first coarse code generating unit for producing the second coarse code signal in order that the feedback pull-down resistance has a level corresponding to a reference resistance; and 
 a first fine code generating unit for producing the second fine code signal in order that the feedback pull-down resistance has a level corresponding to the reference resistance while the first coarse code signal generating unit is inactivated, and 
   wherein the first coarse code generating unit includes:
 a level detecting unit for outputting a pull-down detecting signal by detecting a level of the feedback pull-down resistance based on the reference resistance in response to a first control signal; 
 an amplifier for amplifying the pull-down detecting signal in response to a second control signal and for outputting the amplified signal as a pull-down level signal; 
 a first register control unit for activating a first pull-down driving signal in response to the first control signal and for producing a second pull-down driving signal when the pull-down level signal goes from a first logic level to a second logic level; and 
 a first coarse register for generating the second coarse code signal based on a logic level of the pull-down level signal in response to a third control signal and the first pull-down driving signal.  
   
     
     
       17. The on-die termination circuit of claim 16, wherein:
 the first termination resistance supply unit is a termination pull-up resistance supply unit; and   the second termination resistance supply unit is a termination pull-down resistance supply unit.    
     
     
       18. The on-die termination circuit of claim 16, wherein:
 the first control signal is a first level signal; and   the second control signal is a second level signal.    
     
     
       19. The on-die termination circuit of claim 16, wherein:
 the first comparator is a first differential amplifier; and   the second comparator is a second differential amplifier.