Low voltage receiver circuit and method for shifting the differential input signals of the receiver depending on a common mode voltage of the input signals
First Claim
1. A receiver, comprising:
- a detect circuit coupled to produce a control signal depending solely on a common mode voltage of a pair of differential input signals;
a level shift circuit coupled to receive the pair of differential input signals, and reduce the common mode voltage upon receiving the control signal; and
a sense circuit coupled to receive the reduced said common mode voltage.
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Accused Products
Abstract
An improved communication system, receiver, and method are provided that can reduce input voltages received by the receiver whenever those voltages extend upward to the maximum common-mode voltage range. A detect circuit determines whether the input voltages are at or near the maximum range. If so, the detect circuit sends a control signal to a level shift circuit which will reduce the input voltages by a predefined amount. The reduced voltages can then be forwarded to a sense circuit which preferably operates at a power supply voltage that is less than the maximum differential input voltage (i.e., the maximum voltage on the differential pair of signals), or less than the maximum common-mode voltage of the differential input signals. The sense circuit can thereby operate at a relatively wide common-mode voltage range, and utilizes a lower power supply voltage. The sense circuit can also be made up of a relatively simple differential pair of transistors with corresponding resistor loads in order to sense a differential input voltage range of, for example, 800 millivolts to 2.4 volts prior to voltage reduction, and 800 millivolts to 2.0 volts after voltage reduction.
141 Citations
21 Claims
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1. A receiver, comprising:
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a detect circuit coupled to produce a control signal depending solely on a common mode voltage of a pair of differential input signals;
a level shift circuit coupled to receive the pair of differential input signals, and reduce the common mode voltage upon receiving the control signal; and
a sense circuit coupled to receive the reduced said common mode voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
a pair of resistors coupled between the sense circuit and a corresponding pair of terminals to receive the pair of differential input signals; and
a pair of transistors coupled between the sense circuit and the corresponding pair of resistors to, upon receipt of the control signal, form a current path through the pair of resistors and thereby allow a voltage drop between the pair of terminals and the sense circuit.
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9. The receiver as recited in claim 8, wherein the sense circuit comprises a pair of transistors having a gate or base terminal coupled to the corresponding pair of transistors and pair of transistors.
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10. A transmission system, comprising:
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a driver coupled to produce a pair of differential signals;
a transmission path;
a receiver coupled to receive the pair of differential signals via the transmission path, and wherein the receiver comprises;
a detect circuit coupled to produce a control signal whenever a common mode voltage of the pair of differential signals exceeds a pre-defined amount;
a level shift circuit that, upon receiving the control signal, reduces each voltage of the pair of differential signals, so that the maximum voltage of said each voltage exceeds a supply voltage, but does not exceed the supply voltage by more than the pre-determined amount; and
a sense circuit coupled to receive the reduced each said voltage of the pair of differential signals. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of adjusting differential input signals, comprising:
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when a common mode voltage of the differential input signals exceeds a pre-defined amount, reducing the voltages of the differential input signals;
when a common mode voltage of the differential input signals does not exceed a pre-defined amount, not reducing the voltages of the differential input signals; and
forwarding the reduced or non-reduced differential input signals to a sense circuit. - View Dependent Claims (20, 21)
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Specification