Off-chip driver circuit
First Claim
Patent Images
1. An off-chip driver circuit having a first input terminal and an output terminal, the off-chip driver circuit comprising:
- a pull-up transistor connected between a supply voltage and the output terminal, the pull-up transistor having a control terminal connected to the first input terminal;
an overshoot detection circuit connected to the output terminal, the overshoot detection circuit supplying at its output an overshoot signal when an overshoot voltage at the output terminal is detected; and
a clamping circuit connected between the first input terminal and a reference voltage, the clamping circuit having an input connected to the output of the overshoot detection circuit, the clamping circuit for clamping the first input terminal to the reference voltage.
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Abstract
An off-chip driver circuit can operate in an output mode to drive a signal supplied at its input terminals to an output terminal. It can also operate in an input mode in which signals are driven from an external circuit via the output terminal onto the chip. In an output mode, the output terminal is clamped to reduce the effect of overshoot voltages, for example as a result of reflections from the external circuits.
18 Citations
21 Claims
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1. An off-chip driver circuit having a first input terminal and an output terminal, the off-chip driver circuit comprising:
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a pull-up transistor connected between a supply voltage and the output terminal, the pull-up transistor having a control terminal connected to the first input terminal; an overshoot detection circuit connected to the output terminal, the overshoot detection circuit supplying at its output an overshoot signal when an overshoot voltage at the output terminal is detected; and a clamping circuit connected between the first input terminal and a reference voltage, the clamping circuit having an input connected to the output of the overshoot detection circuit, the clamping circuit for clamping the first input terminal to the reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An off-chip driver circuit having at least one input terminal and an output terminal, said off-chip driver circuit including:
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a pull-up transistor connected between a supply voltage and the output terminal, the pull-up transistor having a control terminal connected to said at least one input terminal when the off-chip driver circuit is used in an output mode; a clamping circuit including a clamping transistor having a controllable path connected between the first input terminal and a reference voltage and a control terminal connected to receive an overshoot signal; and an overshoot detection transistor having a controllable path connected between said output terminal and an overshoot detection node, said overshoot detection node supplying said overshoot signal to said clamping transistor when an overshoot voltage on the output terminal is detected. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An off-chip driver circuit having at least one input terminal and an output terminal, said off-chip driver circuit including:
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a pull-up transistor connected between a supply voltage and the output terminal, the pull-up transistor having a control terminal connected to said at least one input terminal when the off-chip driver circuit is used in an output mode; a clamping circuit including a clamping transistor having a controllable path connected between the first input terminal and a reference voltage and a control terminal connected to receive an overshoot signal; an overshoot detection transistor having a controllable path connected between said output terminal and an overshoot detection node, said overshoot detection node supplying said overshoot signal to said clamping transistor when an overshoot voltage on the output terminal is detected; and a pass gate connected between said at least one input terminal and the control terminal of the pull-up transistor.
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Specification