Input/output circuit for use with various voltages
First Claim
1. An input/output circuit having a terminal for either receiving an input signal or providing an output signal, comprising:
- differential amplifier means having a noninverting input coupled to the terminal, an inverting input, and an output, the differential amplifier having a predetermined offset voltage between the noninverting and inverting inputs and providing in response to a control signal an output voltage which is proportional to a differential input voltage potential between the inverting and noninverting inputs;
output driver means having an output, for providing a driver output signal in response to both the output voltage of the differential amplifier and an output enable signal;
current sensing means coupled between the terminal and the output of the output driver means, for regulating the driver output signal and limiting current at the terminal; and
reference voltage means coupled between the inverting input of the differential amplifier means and the output of the output driver means, for coupling an input voltage having a predetermined relationship to the magnitude of the driver output signal to the inverting input of the differential amplifier means.
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Accused Products
Abstract
An I/O circuit is provided having a terminal for either receiving an input signal or providing an output signal. In one form, the circuit may be utilized in a system with multiple I/O circuits coupled via a two-wire interconnection having a common ground conductor throughout the system. Input signal levels are sensed within a narrow voltage range referenced, in part, to the Vbe of a bipolar transistor and independent of the power supply voltage of other interconnected circuits. In response to an enable signal, a differential amplifier provides an output drive signal proportional to the difference between the signal at the terminal and a reference voltage. The output drive signal is coupled to a driver stage which provides a predetermined limited current at the terminal, thereby providing an output signal. A voltage limiter allows the circuit to use bipolar transistors in a P-well CMOS process and to receive input voltages greater than the supply voltage of the circuit.
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Citations
12 Claims
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1. An input/output circuit having a terminal for either receiving an input signal or providing an output signal, comprising:
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differential amplifier means having a noninverting input coupled to the terminal, an inverting input, and an output, the differential amplifier having a predetermined offset voltage between the noninverting and inverting inputs and providing in response to a control signal an output voltage which is proportional to a differential input voltage potential between the inverting and noninverting inputs; output driver means having an output, for providing a driver output signal in response to both the output voltage of the differential amplifier and an output enable signal; current sensing means coupled between the terminal and the output of the output driver means, for regulating the driver output signal and limiting current at the terminal; and reference voltage means coupled between the inverting input of the differential amplifier means and the output of the output driver means, for coupling an input voltage having a predetermined relationship to the magnitude of the driver output signal to the inverting input of the differential amplifier means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An input/output circuit having a terminal for either receiving an input signal or providing an output signal, comprising:
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a differential amplifier having a noninverting input coupled to the terminal, an inverting input, and an output, for providing, in response to an enable signal, an output signal which is proportional to a difference in input voltage potential between the inverting and noninverting inputs; a first transistor coupled to the differential amplifier for selectively providing a first driver output signal in response to the output signal of the differential amplifier means; a second transistor coupled to a supply voltage terminal for selectively providing a second driver output signal in response to the enable signal; current sensing means having a first terminal coupled to both the first and second transistors, and a second terminal coupled to the terminal, for regulating the first and second driver output signals and for limiting current at the terminal; and reference voltage means coupled between the first terminal of the current sensing means and the inverting input of the differential amplifier means, said reference voltage means having a voltage follower for providing a follower voltage having a magnitude related to the magnitude of the first and second driver output signals to the inverting input of the differential amplifier means. - View Dependent Claims (11, 12)
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Specification