# US 10,484,089 B1 · Driver assisted by charge sharing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,484,089 B1 - Document ID: US10484089B1 - Status: Granted - Kind: B1 - Application number: 15/965,773 - Filed: 2018-04-27 - Published: 2019-10-31 - Granted: 2019-11-19 - Earliest claimed: 2018-04-27 - Assignees: Hewlett Packard Enterprise Development LP - Applicants: Hewlett Packard Enterprise Development LP - Inventors: Zhubiao Zhu; Clinton Harold Parker; Daniel Alan Berkram - Web page: https://patentgrep.com/patent/US10484089B1 ## CPC - H04B 10/07953: {Monitoring or measuring OSNR, BER or Q} - H04B 10/502: {LED transmitters} - H04B 10/58: Compensation for non-linear transmitter output - H04L 25/03343: {Arrangements at the transmitter end} - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A device, including a switch configured to couple a current source with an output terminal upon receipt of a data signal, is provided. The device also includes a first variable capacitor coupled in parallel to the current source at a common node on a source terminal of the switch, wherein the first variable capacitor comprises multiple capacitive elements coupled in parallel and configured to be activated by a programmable signal, and wherein the programmable signal is selected to increase a charge transfer rate from an output terminal coupled to a load, when the switch is turned on. A system and a serial interface including the above device are also provided. ## Claims ### Claim 1 A device, comprising: a switch configured to couple a current source with an output terminal upon receipt of a data signal; and a first variable capacitor coupled in parallel to the current source at a common node on a source terminal of the switch, wherein the first variable capacitor comprises multiple capacitive elements coupled in parallel and configured to be activated by a programmable signal, and wherein the programmable signal is selected to increase a charge transfer rate from an output terminal coupled to a load, when the switch is turned on. ### Claim 2 (depends on 1) The device of claim 1, wherein the switch comprises at least one of a negative channel field effect transistor or a positive channel field effect transistor. ### Claim 3 (depends on 1) The device of claim 1, wherein the multiple capacitive elements comprise at least one field effect transistor coupled in series with a capacitor, and the programmable signal comprises a bit signal to a gate of the field effect transistor. ### Claim 4 (depends on 1) The device of claim 1, wherein the current source comprises a sink terminal of an auxiliary current source configured to maintain a voltage of the common node at a fixed value when a current lower than a bias current is provided to a load. ### Claim 5 (depends on 1) The device of claim 1, wherein the current source comprises a source terminal of a main current source configured to provide a current through a resistor having a first terminal at an output node and a second terminal at the common node, the current flowing from the first terminal to the second terminal to induce a current lower than a bias current through a load coupled in parallel with the source terminal. ### Claim 6 (depends on 1) The device of claim 1, wherein the current source comprises a source terminal of an auxiliary current source configured to maintain a voltage of the common node at a fixed value when a current higher than a bias current is provided to a load. ### Claim 7 (depends on 1) The device of claim 1, wherein the current source comprises a sink terminal of a main current source configured to provide a current through a resistor having a first terminal at the common node and a second terminal at an output node, the current flowing from the first terminal to the second terminal configured to induce a current higher than a bias current through a load. ### Claim 8 (depends on 1) The device of claim 1, further comprising a second variable capacitor coupled in parallel to a source terminal of a main current source, wherein the second variable capacitor comprises multiple capacitive elements coupled in parallel and configured to be activated by a programmable signal, and wherein the programmable signal is selected to increase a charge transfer rate from the output terminal when a second switch activates the source terminal of the main current source. ### Claim 9 (depends on 1) The device of claim 1, wherein a capacitance of the first variable capacitor is adjusted based on a slew rate of a load coupled to the current source. ### Claim 10 (depends on 1) The device of claim 1, wherein a capacitance of the first variable capacitor is adjusted based on a rising slew rate of a load coupled to the current source, and on a falling slew rate of the load. ### Claim 11 A system, comprising: a light emitting device; a data channel configured to provide a data signal; a switch configured to couple a current source with the light emitting device upon receipt of the data signal; and a first variable capacitor coupled in parallel to the current source at a common mode node on a source terminal of the switch, wherein the first variable capacitor comprises a plurality of capacitive elements coupled in parallel and configured to be activated by a programmable signal, and wherein the programmable signal is selected to increase a slew rate from the light emitting device when the switch is turned on and when the switch is turned off. ### Claim 12 (depends on 11) The system of claim 11, further comprising a processor configured to provide the programmable signal to improve a slew rate of the light emitting device. ### Claim 13 (depends on 11) The system of claim 11, wherein the light emitting device comprises a load having a slew rate that defines an eye opening pattern in a bit-error rate diagram. ### Claim 14 (depends on 11) The system of claim 11, wherein a capacitance of the first variable capacitor is adjusted based on a slew rate of a load coupled to the current source and a bit-error rate of an output signal from the light emitting diode. ### Claim 15 A serial interface, comprising: an opto-electronic data link, comprising: a light emitting device configured to convert an electric input signal into an optical output signal; a data channel configured to provide the electric input signal; a switch configured to couple a current source with the light emitting device upon receipt of the electric input signal; and a variable capacitor coupled in parallel to the current source at a common node on a source terminal of the switch, wherein the variable capacitor comprises multiple capacitive elements coupled in parallel and configured to be activated by a programmable signal, and wherein the programmable signal is selected to reduce a bit error rate between the electric input signal and the optical output signal. ### Claim 16 (depends on 15) The serial interface of claim 15, further comprising a processor configured to provide the programmable signal according to a bit error rate measured for the optical output signal. ### Claim 17 (depends on 15) The device of claim 15, wherein the switch comprises at least one of a negative channel field effect transistor or a positive channel field effect transistor. ### Claim 18 (depends on 15) The device of claim 15, further comprising a second variable capacitor coupled in parallel to a source terminal of a main current source, wherein the second variable capacitor comprises multiple capacitive elements coupled in parallel and configured to be activated by a programmable signal, and wherein the programmable signal is selected to differentially increase a rising slew rate and a falling slew rate of an optical signal from the light emitting diode. ### Claim 19 (depends on 15) The device of claim 15, wherein the multiple capacitive elements comprise at least one field effect transistor coupled in series with a capacitor, and the programmable signal comprises a bit signal to a gate of the field effect transistor. ### Claim 20 (depends on 15) The device of claim 15, wherein the current source comprises a sink terminal of an auxiliary current source configured to maintain a voltage of the common node at a fixed value when a current lower than a bias current is provided to a load.