Semiconductor integrated circuit with termination circuit
First Claim
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1. A semiconductor integrated circuit comprising:
- a termination circuit for terminating a bus line;
an impedance control circuit for controlling an impedance of the termination circuit depending on an impedance of an external reference resistance, so as to have the same or substantially the same impedance as that of the external reference resistance; and
a detection circuit for detecting whether the external reference resistance is electrically connected to the semiconductor integrated circuit and disabling the impedance control circuit depending on a detection result.
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Abstract
A semiconductor integrated circuit device which includes a termination circuit for terminating a bus line. An impedance control circuit controls impedance of the termination circuit in accordance with impedance of an external reference resistor, so as to have the same or substantially the same impedance as that of the external reference resistor. A detection circuit detects whether the external reference resistor is electrically connected to the semiconductor integrated circuit, and disables the impedance control circuit based on a detection result.
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Citations
21 Claims
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1. A semiconductor integrated circuit comprising:
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a termination circuit for terminating a bus line;
an impedance control circuit for controlling an impedance of the termination circuit depending on an impedance of an external reference resistance, so as to have the same or substantially the same impedance as that of the external reference resistance; and
a detection circuit for detecting whether the external reference resistance is electrically connected to the semiconductor integrated circuit and disabling the impedance control circuit depending on a detection result. - View Dependent Claims (2, 3, 4, 5, 10)
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6. A semiconductor integrated circuit comprising:
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a first pad connected to a bus line;
a second pad connected to an external reference resistance;
a first variable impedance circuit connected between a power supply voltage and the first pad;
a second variable impedance circuit connected between a ground supply voltage and the first pad;
a first comparator for comparing a voltage of the second pad with a reference voltage to output a count signal;
a counter for generating an impedance control signal for controlling impedance of the first and second variable impedance circuits, in response to the count signal; and
a detection circuit connected to the second pad, for detecting whether the external reference resistance is electrically connected to the semiconductor integrated circuit, wherein the detection circuit disables the first comparator and the counter when the external reference resistance is not connected to the semiconductor integrated circuit. - View Dependent Claims (7, 8, 11)
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9. A semiconductor integrated circuit comprising:
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a first pad connected to a bus line;
a second pad connected to an external reference resistor;
a first variable impedance circuit connected between a power supply voltage and the first pad;
a second variable impedance circuit connected between a ground supply voltage and the first pad;
a comparator for comparing a voltage of the second pad with a reference voltage to output a count signal;
a counter for generating an impedance control code for controlling impedance of the first and second variable impedance circuits, in response to the count signal; and
a detection circuit for detecting whether the external reference resistor is electrically connected to the semiconductor integrated circuit, depending on the impedance control code, wherein the detection circuit disables the first comparator and the counter when the impedance control code indicates that the external reference resistor is not connected to the semiconductor integrated circuit. - View Dependent Claims (12)
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13. A detection circuit, comprising:
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a connection to a bonding pad of a semiconductor integrated circuit; and
a circuit for detecting whether a reference resistance, external to the semiconductor integrated circuit, is electrically connected to the semiconductor integrated circuit and disabling an impedance control circuit of the semiconductor integrated circuit depending on a detection result. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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Specification