True-differential DVI/HDMI line driver
First Claim
1. A line driver for differential signal output, comprisinga current source connecting to a first stable voltage source;
- a pair of current-steering metal-oxide-semiconductor field-effect transistors with their drain terminals connecting together and to the current source, and source terminals connecting to the differential output signal nodes of the driver, receiving at their gate inputs a true and complementary differential signal pair;
and a pair of controlled switch devices, each connecting to an output signal node and a current-steering transistor'"'"'s source node at one conducting terminal, and at its other conducting terminal through a transmitter termination impedance to a second stable voltage source, receiving at their control inputs the true and complementary differential signal pair.
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Abstract
A novel source-coupled differential driver circuit fully compatible with digital visual interface (DVI/HDMI) signaling specification is disclosed. Driven output signals are connected to the source terminals of driving switches in the invention circuit, minimizing the detrimental impact of miller coupling capacitance between gate nodes and driven output nodes upon output slew-rate, enabling higher frequencies of operation. Undriven output wires are connected to source-termination impedances, providing a matched return current to the driven current signal, and reducing return path impedance substantially. Matched differential current drive from the source ensures true-differential signaling, eliminating shield current flow and improving signal integrity. Bit error rate (BER) is reduced and overall link performance is significantly enhanced due to improved slew rates, true-differential signaling and greater signal integrity, enabling long reach and high-speed, high-definition multi-media data transmission.
42 Citations
19 Claims
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1. A line driver for differential signal output, comprising
a current source connecting to a first stable voltage source; -
a pair of current-steering metal-oxide-semiconductor field-effect transistors with their drain terminals connecting together and to the current source, and source terminals connecting to the differential output signal nodes of the driver, receiving at their gate inputs a true and complementary differential signal pair; and a pair of controlled switch devices, each connecting to an output signal node and a current-steering transistor'"'"'s source node at one conducting terminal, and at its other conducting terminal through a transmitter termination impedance to a second stable voltage source, receiving at their control inputs the true and complementary differential signal pair. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 18)
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14. A method for differential output signal generation, comprising:
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steering a current through a field-effect transistor into a driven output signal wire such that the driving signal steering the current is in phase with the output voltage developed; while simultaneously activating a switch connecting the complementary output signal wire through terminating impedances or current limiting circuits to a termination reference voltage so as to provide a matched current flow in the complementary output signal wire of a polarity opposite to that of the steered current flow in the driven output signal wire. - View Dependent Claims (15, 16, 17, 19)
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Specification