# US 9,520,842 B2 · Transmission line driver circuit for adaptively calibrating impedance matching > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,842 B2 - Document ID: US9520842B2 - Status: Granted - Kind: B2 - Application number: 14/842,285 - Filed: 2015-09-01 - Published: 2016-04-07 - Granted: 2016-12-13 - Earliest claimed: 2014-10-01 - Assignees: Realtek Semiconducor Corp. - Applicants: Realtek Semiconductor Corp. - Inventors: Chao-Cheng Lee; Jian-Ru Lin; Chien-Ming Wu; Shih-Wei Wang - Web page: https://patentgrep.com/patent/US9520842B2 ## CPC - H03F 1/56: Modifications of input or output impedances, not otherwise provided for - H03F 3/45475: {using IC blocks as the active amplifying circuit} - H03H 7/40: Automatic matching of load impedance to source impedance - H03F 2200/114: the amplifier comprising means for electro-magnetic interference [EMI] protection - H03F 2200/387: A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier - H03F 2203/45008: the addition of two signals being made by a resistor addition circuit for producing the common mode signal - H03F 2203/45022: One or more added resistors to the amplifying transistors in the differential amplifier - H03F 2203/45686: the LC comprising one or more potentiometers, which are not shunting potentiometers - H03F: AMPLIFIERS - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract A transmission line driver circuit includes: a transmission line driving amplifier having a first transmission terminal and a second transmission terminal; a first signal node; a second signal node; a first adjustable resistor positioned between the first transmission terminal and the first signal node; a second adjustable resistor positioned between the second transmission terminal and the second signal node; an internal node; a first divider resistor positioned between the first signal node and the internal node; a second divider resistor positioned between the second signal node and the internal node; a comparing circuit for comparing a divided voltage at the internal node with a reference voltage to generate a comparison signal; and an adjusting circuit for adjusting resistance of at least one of the first and second adjustable resistors according to the comparison signal. ## Claims ### Claim 1 A transmission line driver circuit for adaptively calibrating impedance matching, comprising: a transmission line driving amplifier comprising a first transmission terminal and a second transmission terminal for providing a pair of differential transmission signals; a first signal node for coupling with a first load-end signal node of an equivalent load circuit; a second signal node for coupling with a second load-end signal node of the equivalent load circuit; a first adjustable resistor positioned on a signal path between the first transmission terminal and the first signal node; a second adjustable resistor positioned on a signal path between the second transmission terminal and the second signal node; an internal node; a first divider resistor, wherein a first terminal of the first divider resistor is coupled with a signal path between the first adjustable resistor and the first signal node, and a second terminal of the first divider resistor is coupled with the internal node; a second divider resistor, wherein a first terminal of the second divider resistor is coupled with a signal path between the second adjustable resistor and the second signal node, and a second terminal of the second divider resistor is coupled with the internal node; a comparing circuit, coupled with the internal node, configured to operably compare a reference voltage with a divided voltage at the internal node to generate a comparison signal; and an adjusting circuit, coupled with the first adjustable resistor, the second adjustable resistor, and the comparing circuit, configured to operably adjust resistance of at least one of the first adjustable resistor and the second adjustable resistor according to the comparison signal. ### Claim 2 (depends on 1) The transmission line driver circuit of claim 1, wherein the first signal node and the second signal node are a pair of differential signal nodes of a medium dependent interface (MDI). ### Claim 3 (depends on 1) The transmission line driver circuit of claim 1, wherein the first signal node and the second signal node are a pair of differential signal node of a medium dependent interface crossover (MDIX). ### Claim 4 (depends on 1) The transmission line driver circuit of claim 1, wherein the comparing circuit is a hysteresis comparator. ### Claim 5 (depends on 1) The transmission line driver circuit of claim 1, wherein the reference voltage is a common mode voltage provided by the transmission line driving amplifier. ### Claim 6 (depends on 5) The transmission line driver circuit of claim 5, wherein when the comparison signal is oscillated between a positive polarity and a negative polarity, the adjusting circuit adjusts the resistance of at least one of the first adjustable resistor and the second adjustable resistor to render the comparison signal to stay in either the positive polarity or the negative polarity. ### Claim 7 (depends on 6) The transmission line driver circuit of claim 6, wherein the adjusting circuit gradually adjusts the resistance of the first adjustable resistor or the resistance of the second adjustable resistor in multiple calibration cycles until the comparison signal stays in either the positive polarity or the negative polarity. ### Claim 8 (depends on 6) The transmission line driver circuit of claim 6, wherein the adjusting circuit directly reduces the resistance of the first adjustable resistor to a first target value or directly increases the resistance of the second adjustable resistor to a second target value in a single calibration cycle to render the comparison signal to stay in either the positive polarity or the negative polarity.