On-die termination circuit and driving method thereof

摘要

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.

主权项

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.