LVDS input circuit with extended common mode range
First Claim
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1. An apparatus, comprising:
- a first resistor coupled between a differential logic circuit and a first input pad;
a second resistor coupled between the differential logic circuit and a second input pad;
a first and a second termination resistors coupled to the first and the second input pads, respectively, the first and second termination resistors being coupled to each other in series at a node to produce a common mode reference voltage at the node;
a plurality of pull-up current mirrors coupled to the first and second resistors; and
a plurality of pull-down current mirrors coupled to the first and second resistors.
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Abstract
A low voltage differential signal (LVDS) input circuit with extended common mode range has been disclosed. One embodiment of the LVDS input circuit includes a first resistor coupled between a differential logic circuit and a first input pad, a second resistor coupled between the differential logic circuit and a second input pad, and a first and a second termination resistors coupled to the first and the second input pads, respectively, the first and second termination resistors being coupled to each other in series at a node to produce a common mode reference voltage at the node. Other embodiments are described and claimed.
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Citations
16 Claims
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1. An apparatus, comprising:
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a first resistor coupled between a differential logic circuit and a first input pad; a second resistor coupled between the differential logic circuit and a second input pad; a first and a second termination resistors coupled to the first and the second input pads, respectively, the first and second termination resistors being coupled to each other in series at a node to produce a common mode reference voltage at the node; a plurality of pull-up current mirrors coupled to the first and second resistors; and a plurality of pull-down current mirrors coupled to the first and second resistors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method, comprising:
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translating a first and a second low voltage differential signal (LVDS) input signals into a first and a second differential input signals through a first and a second translation resistors, respectively, within a LVDS input circuit; inputting the first and the second differential input signals to a differential logic circuit within the LVDS input circuit; dividing a difference between the first and the second LVDS input signals over a first and a second termination resistors, which are coupled to each other in series, to produce a common mode reference voltage at a node between the first and the second termination resistors; and setting currents through a plurality of pull-up current mirrors, a plurality of pull-down current mirrors, a first resistor, and a second resistor using the common mode reference voltage to cause a difference between the differential input signals to be substantially constant, wherein the first resistor is coupled between the node and the plurality of pull-up current mirrors and the second resistor is coupled between the node and the plurality of pull-down current mirrors. - View Dependent Claims (10, 11)
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12. An apparatus, comprising:
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means for extending an upper limit of a common mode range of a first and a second low voltage differential signal (LVDS) input signals beyond a power supply voltage provided to the LVDS input circuit; and means for producing a first and a second substantially constant differential input signals from the first and the second LVDS input signals, wherein the means for producing a first and a second substantially constant differential input signals comprises a plurality of pull-up current mirrors and a plurality of pull-down current mirrors. - View Dependent Claims (13, 14)
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15. A method, comprising:
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translating a pair of differential signals to modify a common mode voltage of the pair of differential signals such that the translated pair of differential signals is compatible with a differential Metal Oxide Semiconductor (MOS) amplifier; inputting the translated pair of differential signals into the differential MOS amplifier; and setting currents through a plurality of pull-up current mirrors and a plurality of pull-down current mirrors to cause a difference between the pair of differential signals to be substantially constant. - View Dependent Claims (16)
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Specification