Output circuit for semiconductor device, semiconductor device having output circuit, and method of adjusting characteristics of output circuit
DC CAFCFirst Claim
1. An output circuit for a semiconductor device, comprising:
- a plurality of impedance-adjustable unit buffers connected in common to a data pin, the plurality of unit buffers being divided into at least first and second groups, each unit buffer including a plurality of parallel-connected transistors each individually on/off controlled;
a first pre-stage circuit that activates one or more unit buffers belonging to the first group;
a second pre-stage circuit that activates one or more unit buffers belonging to the second group; and
an output control circuit that independently selects the first and second pre-stage circuits.
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Abstract
To decrease the circuit scale necessary for the calibration of the output circuit and to decrease the time required for the calibration operation. The invention includes a first output buffer and a second output buffer that are connected to a data pin, and a calibration circuit that is connected to a calibration pin. The first output buffer and the second output buffer include plural unit buffers. The unit buffers have mutually the same circuit structures. With this arrangement, the impedances of the first output buffer and the second output buffer can be set in common, based on the calibration operation using the calibration circuit. Consequently, both the circuit scale necessary for the calibration operation and the time required for the calibration operation can be decreased.
30 Citations
35 Claims
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1. An output circuit for a semiconductor device, comprising:
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a plurality of impedance-adjustable unit buffers connected in common to a data pin, the plurality of unit buffers being divided into at least first and second groups, each unit buffer including a plurality of parallel-connected transistors each individually on/off controlled; a first pre-stage circuit that activates one or more unit buffers belonging to the first group; a second pre-stage circuit that activates one or more unit buffers belonging to the second group; and an output control circuit that independently selects the first and second pre-stage circuits. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An output circuit for a semiconductor device, comprising:
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a first output buffer having parallel-connected two or more impedance-adjustable unit buffers connected in common to a data pin; and a second output buffer having one or parallel-connected two or more impedance-adjustable unit buffers connected in common to the data pin, wherein the unit buffers have mutually substantially the same circuit structures, each unit buffer included in the first and second output buffers includes a plurality of parallel-connected transistors each individually on/off controlled, and a number of unit buffers included in the first output buffer is different from that of the second output buffer. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. An output circuit for a semiconductor device that can perform ODT operation, comprising:
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a plurality of impedance-adjustable unit buffers connected in common to a data pin, each unit buffer including a plurality of parallel-connected transistors each individually on/off controlled; and an output control circuit that activates a first number of unit buffers in common when an ODT impedance is set to a first value and activates a second number of unit buffers in common when the ODT impedance is set to a second value. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35)
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Specification