An impedance matching circuit performs a ZQ calibration for a test on a wafer process of a semiconductor memory device. The impedance matching circuit of the semiconductor memory device includes a first pull-down resistance unit, a first pull-up resistance unit, a second pull-up resistance unit and a second pull-down resistance unit. The first pull-down resistance unit supplies a ground voltage to a first node in response to a calibration test signal. The first pull-up resistance unit calibrates its resistance to that of the first pull-down resistance unit to thereby generate a pull-up calibration code. The second pull-up resistance unit supplies a supply voltage to a second node in response to the pull-up calibration code. The second pull-down resistance unit calibrates its resistance to that of the second pull-up resistance unit to thereby generate a pull-down calibration code.

Impedance matching circuit and semiconductor memory device with the same

A method, system, and output driver calibration circuit determine calibration values for configuring adjustable impedance output drivers. The calibration circuit includes a pull-up calibration circuit configured to generate an averaged pull-up count signal for calibrating p-channel devices in the output driver with the averaged pull-up count signal being an average of a plurality of pull-up count signals. The calibration circuit further includes a pull-down calibration circuit configured to generate an averaged pull-down count signal for calibrating n-channel devices in the output driver with the averaged pull-down count signal being an average of a plurality of pull-down count signals.

Method and apparatus for output driver calibration, and memory devices and system embodying same

Described are on-die termination (ODT) systems and methods that facilitate high-speed communication between a driver die and a receiver die interconnected via one or more signal transmission lines. An ODT control system in accordance with one embodiment calibrates and maintains termination resistances and drive currents to produce optimal output swing voltages. Comparison circuitry employed to calibrate the reference resistance is also used to calibrate the drive current. Termination elements in some embodiments are divided into two adjustable resistive portions, both of which are designed to minimize capacitive loading. One portion is optimized to produce a relatively high range of adjustment, while the other is optimized for fine-tuning and glitch-free switching.

Calibration methods and circuits to calibrate drive current and termination impedance

A plurality of transistor pairs of Pch and Nch transistors are connected in series between VDD and GND. An I/O terminal is connected to each connection point of the transistor pairs. Two transistor pairs constitute one transistor set, in which each of two Pch transistors and two Nch transistors have the same on-resistance. In input mode, one of the two transistor pairs in a first set is turned on, and a transistor pair of a second or later set is selectively turned on. In output mode, two Pch transistors or two Nch transistors of the first set are turned on, and a transistor of the second or later set is selectively turned on.

I/O interface circuit of integrated circuit

A variable impedance sense (VIS) circuit ( 600 ) can detect and store an input offset value inherent in a sensing loop ( 620 and/or 622 ). According to a detected input offset polarity, a resulting impedance matching binary code can be adjusted to compensate for error that can be introduced by the input offset. The binary code can also be adjusted to compensate for additional error that can be introduced by dropping a least significant bit (LSB) of the code to reduce noise effects caused by the switching of the LSB.

Variable impedance sense architecture and method

A method for producing a stable control signal for impedance matching is provided which is capable of suppressing variation in impedance matching data by adding a shift voltage to a voltage to be compared. A comparator compares the voltage to be compared with a reference voltage and an up-down counter performs a counting operation according to a result from the comparison. A code converting circuit converts a count value output from the up-down counter to a thermometer code used for changing an impedance of an impedance varying circuit. A change in the impedance is made in a manner that, even when the voltage to be compared gets closest to the reference voltage, a shift voltage for the comparator to make an exact comparison is fed to the voltage to be compared. An averaging circuit averages a count value and the code converting circuit converts a resulting average value to the thermometer code.

Ohno Tsuyoshi

Papers

Method and circuit for producing control signal for impedance matching