Output driver circuit with well-controlled output impedance
First Claim
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1. An output driver circuit including an output for coupling to a conductor of a signal line, the output having an output impedance, the output driver circuit comprising:
- a driver circuit having an output; and
a passive network coupled to the output of the driver circuit and to the output of the output driver circuit, the passive network configured to limit variation in the output impedance to a predefined range while the output driver circuit operates within a predefined range of expected operating conditions.
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Abstract
An output driver circuit for driving a signal onto a signal line. The output driver circuit comprises at least one driver circuit and a passive network. The passive network is configured to limit the variation in the output impedance of the output driver circuit. The output driver circuit thus provides an output impedance that closely matches the loaded impedance of the signal line at all times so as to minimize secondary reflections on the signal line.
20 Citations
17 Claims
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1. An output driver circuit including an output for coupling to a conductor of a signal line, the output having an output impedance, the output driver circuit comprising:
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a driver circuit having an output; and
a passive network coupled to the output of the driver circuit and to the output of the output driver circuit, the passive network configured to limit variation in the output impedance to a predefined range while the output driver circuit operates within a predefined range of expected operating conditions. - View Dependent Claims (2, 3)
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4. An electronic system for generating and transmitting a digital signal, comprising:
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(1) an output driver circuit, comprising;
(a) a driver circuit having an output;
(b) a passive network coupled to the output of the driver circuit, comprising;
(i) a series resistor including a first end coupled to the output of the driver circuit and a second end;
(ii) a parallel resistor including a first end coupled to the second end of the series resistor and a second end;
(iii) a capacitor coupled between the second end of the parallel resistor and a first voltage supply; and
(iv) an output coupled to the second end of the series resistor and to the first end of the parallel resistor for coupling to the conductor; and
(c) an output coupled to the output of the passive network, the output having an output impedance; and
(2) a signal line, comprising;
(a) a conductor including a first end coupled to the output of the output driver circuit and a second end;
(b) a resistor including a first end coupled to the second end of the conductor and a second end; and
(c) a capacitor coupled between the second end of the resistor and a second voltage supply.
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5. An output driver circuit including first and second outputs for coupling to first and second conductors, respectively, of a differential signal line, the first and second outputs having first and second output impedances, respectively, the output driver circuit comprising:
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a first driver circuit having an output;
a second driver circuit having an output; and
a passive network coupled to the outputs of the first and second driver circuits and to the first and second outputs of the output driver circuit, the passive network configured to limit variation in the first and second output impedances to a predefined range while the output driver circuit operates within a predefined range of expected operating conditions. - View Dependent Claims (6)
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7. An output driver circuit for coupling to a differential signal line having a first conductor and a second conductor, comprising:
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a first driver circuit having an input and an output;
a second driver circuit having an input and an output; and
a passive network coupled to the outputs of the first and second driver circuits and including a first output for coupling to the first conductor and a second output for coupling to the second conductor, comprising;
a first parallel resistor including a first end coupled to the first output of the passive network and a second end coupled to a differential ground node; and
a second parallel resistor including a first end coupled to the second output of the passive network and a second end coupled to the differential ground node. - View Dependent Claims (8, 9, 10, 11, 12)
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13. An electronic system for generating and transmitting a digital signal, comprising:
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(1) an output driver circuit, comprising;
(a) a first driver circuit having an input and an output;
(b) a second driver circuit having an input and an output;
(c) a passive network coupled to the outputs of the first and second driver circuits, comprising;
(i) a first parallel resistor including a first end coupled to a first output of the passive network and a second end coupled to a first differential ground node; and
(ii) a second parallel resistor including a first end coupled to a second output of the passive network and a second end coupled to the first differential ground node; and
(d) first and second outputs coupled to the first and second outputs of the passive network, respectively; and
(2) a signal line, comprising;
(a) a first conductor including a first end coupled to the first output of the output driver circuit and a second end;
(b) a first resistor including a first end coupled to the second end of the first conductor and a second end coupled to a second differential ground node;
(c) a second conductor including a first end coupled to the second output of the output driver circuit and a second end; and
(d) a second resistor including a first end coupled to the second end of the second conductor and a second end coupled to the second differential ground node. - View Dependent Claims (14)
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15. An output driver circuit for coupling to a differential signal line having a first conductor and a second conductor, comprising:
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a first output for coupling to a first end of the first conductor;
a first p-channel transistor including a source coupled to a power supply, a drain coupled to the first output and a gate for receiving a first drive signal having a voltage such that the first p-channel transistor operates in a saturation or cutoff region of operation only;
a first n-channel transistor including a drain coupled to the first output, a source coupled to a ground supply and a gate for receiving a second drive signal having a voltage such that the first n-channel transistor operates in a saturation or cutoff region of operation only;
a first resistor including a first end coupled to the first output and a second end coupled to a differential ground node;
a second output for coupling to a first end of the second conductor;
a second p-channel transistor including a source coupled to the power supply, a drain coupled to the second output and a gate for receiving a third drive signal having a voltage such that the second p-channel transistor operates in a saturation or cutoff region of operation only;
a second n-channel transistor including a drain coupled to the second output, a source coupled to the ground supply and a gate for receiving a fourth drive signal having a voltage such that the second n-channel transistor operates in a saturation or cutoff region of operation only; and
a second resistor including a first end coupled to the second output and a second end coupled to the differential ground node. - View Dependent Claims (16, 17)
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Specification