Semiconductor device and method of adjusting characteristic thereof
AssigneeElpida Memory, Inc.
InventorsKoji Kuroki, Daiki Nakashima, Ryuuji Takishita
Life of this patent
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Abstract
To suppress the number of clocks needed to adjust the impedance of an output buffer. A pull-up replica buffer is connected between a calibration terminal and power supply wiring, and is controlled in impedance by a DRZQP signal supplied from a counter. A pull-down replica buffer is connected between ground wiring and a connection node A, and is controlled in impedance by a DRZQN signal supplied from the counter. More specifically, the DRZQP signal and the DRZQN signal indicate count values. The impedances of the replica buffers are increased or decreased stepwise in proportion to the count values. The count values are updated according to a binary search method.
Claims5
A semiconductor device comprising:
- an output buffer;
- a calibration terminal to be coupled to an external resistor;
- and
- a control circuit coupled to the output buffer and the calibration terminal, controlling an output impedance of the output buffer in response to the external resistor, the control circuit comprising a counter, the output impedance of the output buffer being dependent on a count value of the counter, the count value being represented by a plurality of bits including a most significant bit and a least significant bit, and configured to be changed from one of more significant bits inclusive of the most significant bit,
- wherein the count value is variable under a maximum value and the most significant bit is initialized such that the count value takes a half of the maximum value when the control circuit receives a calibration command.
Dependencies are inferred from the claim text.