Patent ID: RE45246

Claim:
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.