Resistor mirror
First Claim
Patent Images
1. A circuit for providing a termination resistance to a transmission line, the circuit comprising:
- a reference resistor;
a controllable termination resistor, coupled between the transmission line and a termination voltage node, and coupled to and controllable through a control node;
a control circuit, coupled to the reference resistor and the control node; and
a power supply voltage, the termination voltage node at the power supply voltage and the control node capable of having a control voltage of greater magnitude than the power supply voltage.
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Abstract
A circuit that provides a termination resistance to a transmission line includes a controllable termination resistor coupled between the transmission line and a termination voltage node. The circuit also includes a control circuit coupled to the controllable termination resistor and to a reference resistor. The control circuit matches the resistance of the controllable termination resistor to the resistance of the reference resistor.
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Citations
29 Claims
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1. A circuit for providing a termination resistance to a transmission line, the circuit comprising:
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a reference resistor;
a controllable termination resistor, coupled between the transmission line and a termination voltage node, and coupled to and controllable through a control node;
a control circuit, coupled to the reference resistor and the control node; and
a power supply voltage, the termination voltage node at the power supply voltage and the control node capable of having a control voltage of greater magnitude than the power supply voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of terminating a transmission line, the method comprising:
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connecting the transmission line to a controllable termination resistor that is coupled to a power supply voltage in an integrated circuit;
generating a reference electrical value dependent on the resistance of a reference resistor;
generating a termination electrical value dependent on the resistance of the controllable termination resistor; and
using the reference electrical value and the termination electrical value to change a voltage that is greater than the power supply voltage in order to chance the resistance of the controllable termination resistor so that it matches the resistance of the reference resistor. - View Dependent Claims (14, 15, 16)
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17. An apparatus for providing a resistance between a conductor and a termination node, coupled to a supply voltage the apparatus comprising:
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a reference resistor;
a controllable termination resistor, coupled between the termination node and the conductor; and
control means, coupled to the reference resistor and the controllable termination resistor for matching the resistance of the controllable termination resistor to the resistance of the reference resistor by applying a voltage greater than the supply voltage to a portion of the controllable termination resistor. - View Dependent Claims (18, 19)
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20. An electronics system for performing electronics functions, the system comprising:
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an electrical circuit;
transmission means coupled between the electrical circuit and a remote location, for providing a communication path between the electrical circuit and the remote location; and
termination means, coupled between the transmission means and a termination node that provides a supply voltage, the termination means comprising a controllable termination resistor coupled between the transmission means and the termination node, a reference resistor, and control means coupled between the reference resistor and the controllable termination resistor for setting the resistance of the controllable termination resistor equal to a value that is proportional to the resistance of the reference resistor by providing a voltage that is larger than the supply voltage to a portion of the controllable termination resistor. - View Dependent Claims (21)
a plurality of transmission means, coupled between the electrical circuit and the remote location, for providing a plurality of communication paths between the electrical circuit and a plurality of remote locations; and
a plurality of controllable termination resistors coupled between the plurality of transmission means and a termination node, and coupled to the control means, the control means for setting the resistances of the plurality of controllable termination resistors equal to a value that is proportional to the resistance of the reference resistor.
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22. A switching circuit in an integrated circuit having a power supply voltage, the switching circuit comprising:
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an input, the input adapted to be coupled to a voltage greater than the power supply voltage;
a switching transistor, positioned between the input and an output and adapted to operate in a first and second state, in the first state the switching transistor providing a current path from the input to the output, in the second state the switching transistor interrupting a current path from the input to the output;
a control input;
a control circuit, coupled to the control input and the switching transistor; and
a pull down circuit, connected to the control circuit and the output and adapted to lower the voltage at the output when the switching transistor is in the second state while limiting the voltage drop across the switching transistor to less than a voltage at which the switching transistor is damaged. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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Specification