Patents by Inventor Nagesh Surendranath

Nagesh Surendranath has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20220021789
    Abstract: In described examples, a circuit includes an integrator. The integrator receives an input signal. A first sampling network is coupled to the integrator and generates a signal voltage. A second sampling network is coupled to the integrator and generates a pixel sampled noise voltage. The pixel sampled noise voltage generated in a previous cycle is subtracted from the signal voltage generated in a current cycle to generate a true signal voltage.
    Type: Application
    Filed: July 14, 2020
    Publication date: January 20, 2022
    Inventors: Nagesh Surendranath, Sravana Kumar Goli
  • Patent number: 11152903
    Abstract: In accordance with one embodiment, an apparatus includes a first amplifier having a noninverting input, an inverting input and an output. The noninverting input is coupled to a first ground reference. The inverting input is coupled to an output of an external sensor. The apparatus also includes a second amplifier having a noninverting input, an inverting input and an output. The noninverting input is coupled to the first ground reference. The inverting input is coupled to the power supply through a first variable capacitor and to the second ground reference through a second variable capacitor. The output is coupled to the inverting input of the first amplifier. The external sensor is coupled to a third ground reference, and the first amplifier and second amplifier are coupled to the second ground reference.
    Type: Grant
    Filed: October 22, 2019
    Date of Patent: October 19, 2021
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Nagesh Surendranath, Shriram Mahendra Devi, Sravana Kumar Goli
  • Publication number: 20210310863
    Abstract: A dark current compensation circuit comprises a first comparator having inputs for a detection signal and a first voltage, and a second comparator having inputs for the detection signal and a second voltage. The dark current compensation circuit also comprises a controller coupled to the first and second comparators, which has an input for an event signal. An adjustable current source is coupled to the controller and configured to generate a compensation current. The controller adjusts a value of the compensation current based on the first and second comparator outputs and maintains a constant value in response to the event signal indicating photons incident on a photon detector. In some implementations, the dark current compensation circuit further comprises an analog sub-circuit coupled to the adjustable current source and configured to receive the detection signal. The analog sub-circuit generates an analog compensation current in response to the detection signal.
    Type: Application
    Filed: June 16, 2021
    Publication date: October 7, 2021
    Inventors: Rakul VISWANATH, Nagesh SURENDRANATH, Sandeep Kesrimal OSWAL, Ratna Kumar Venkata PARUPUDI
  • Patent number: 11092482
    Abstract: A circuit for use in a system that includes a detector, wherein the circuit comprises an input terminal to receive a detector signal from the detector external to the circuit, the detector signal to include an error charge corresponding to a leakage current. The circuit further comprises an amplifier coupled to the input terminal to receive input signals corresponding to the detector signal, including the error charge applied to an input of the amplifier. The circuit further comprises a feedback path coupled across the amplifier, wherein the feedback path comprises a first switch coupled across a leakage resistor and to a leakage capacitor for discharging a feedback compensation charge from the leakage capacitor and onto the input of the amplifier to substantially cancel the error charge.
    Type: Grant
    Filed: February 15, 2019
    Date of Patent: August 17, 2021
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Nagesh Surendranath, Rakul Viswanath
  • Patent number: 11067440
    Abstract: A dark current compensation circuit comprises a first comparator having inputs for a detection signal and a first voltage, and a second comparator having inputs for the detection signal and a second voltage. The dark current compensation circuit also comprises a controller coupled to the first and second comparators, which has an input for an event signal. An adjustable current source is coupled to the controller and configured to generate a compensation current. The controller adjusts a value of the compensation current based on the first and second comparator outputs and maintains a constant value in response to the event signal indicating photons incident on a photon detector. In some implementations, the dark current compensation circuit further comprises an analog sub-circuit coupled to the adjustable current source and configured to receive the detection signal. The analog sub-circuit generates an analog compensation current in response to the detection signal.
    Type: Grant
    Filed: June 11, 2019
    Date of Patent: July 20, 2021
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Rakul Viswanath, Nagesh Surendranath, Sandeep Kesrimal Oswal, Ratna Kumar Venkata Parupudi
  • Publication number: 20210119594
    Abstract: In accordance with one embodiment, an apparatus includes a first amplifier having a noninverting input, an inverting input and an output. The noninverting input is coupled to a first ground reference. The inverting input is coupled to an output of an external sensor. The apparatus also includes a second amplifier having a noninverting input, an inverting input and an output. The noninverting input is coupled to the first ground reference. The inverting input is coupled to the power supply through a first variable capacitor and to the second ground reference through a second variable capacitor. The output is coupled to the inverting input of the first amplifier. The external sensor is coupled to a third ground reference, and the first amplifier and second amplifier are coupled to the second ground reference.
    Type: Application
    Filed: October 22, 2019
    Publication date: April 22, 2021
    Inventors: Nagesh Surendranath, Shriram Mahendra Devi, Sravana Kumar Goli
  • Publication number: 20210088680
    Abstract: In described examples, a charge sensitive amplifier (CSA) generates an integrated signal in response to a current signal. A high pass filter is coupled to the CSA and receives the integrated signal and an inverse of an event signal, the high pass filter generates a coarse signal. An active comparator is coupled to the high pass filter and receives the coarse signal and a primary reference voltage signal, the active comparator generates the event signal.
    Type: Application
    Filed: December 8, 2020
    Publication date: March 25, 2021
    Inventors: Rakul VISWANATH, Nagesh SURENDRANATH, Sandeep Kesrimal OSWAL, Ratna Kumar Venkata PARUPUDI
  • Patent number: 10890674
    Abstract: In described examples, a charge sensitive amplifier (CSA) generates an integrated signal in response to a current signal. A high pass filter is coupled to the CSA and receives the integrated signal and an inverse of an event signal, the high pass filter generates a coarse signal. An active comparator is coupled to the high pass filter and receives the coarse signal and a primary reference voltage signal, the active comparator generates the event signal.
    Type: Grant
    Filed: January 15, 2019
    Date of Patent: January 12, 2021
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Rakul Viswanath, Nagesh Surendranath, Sandeep Kesrimal Oswal, Ratna Kumar Venkata Parupudi
  • Publication number: 20200393294
    Abstract: A dark current compensation circuit comprises a first comparator having inputs for a detection signal and a first voltage, and a second comparator having inputs for the detection signal and a second voltage. The dark current compensation circuit also comprises a controller coupled to the first and second comparators, which has an input for an event signal. An adjustable current source is coupled to the controller and configured to generate a compensation current. The controller adjusts a value of the compensation current based on the first and second comparator outputs and maintains a constant value in response to the event signal indicating photons incident on a photon detector. In some implementations, the dark current compensation circuit further comprises an analog sub-circuit coupled to the adjustable current source and configured to receive the detection signal. The analog sub-circuit generates an analog compensation current in response to the detection signal.
    Type: Application
    Filed: June 11, 2019
    Publication date: December 17, 2020
    Inventors: Rakul VISWANATH, Nagesh SURENDRANATH, Sandeep Kesrimal OSWAL, Ratna Kumar Venkata PARUPUDI
  • Publication number: 20200264039
    Abstract: A circuit for use in a system that includes a detector, wherein the circuit comprises an input terminal to receive a detector signal from the detector external to the circuit, the detector signal to include an error charge corresponding to a leakage current. The circuit further comprises an amplifier coupled to the input terminal to receive input signals corresponding to the detector signal, including the error charge applied to an input of the amplifier. The circuit further comprises a feedback path coupled across the amplifier, wherein the feedback path comprises a first switch coupled across a leakage resistor and to a leakage capacitor for discharging a feedback compensation charge from the leakage capacitor and onto the input of the amplifier to substantially cancel the error charge.
    Type: Application
    Filed: February 15, 2019
    Publication date: August 20, 2020
    Inventors: Nagesh SURENDRANATH, Rakul VISWANATH
  • Publication number: 20200225370
    Abstract: In described examples, a charge sensitive amplifier (CSA) generates an integrated signal in response to a current signal. A high pass filter is coupled to the CSA and receives the integrated signal and an inverse of an event signal, the high pass filter generates a coarse signal. An active comparator is coupled to the high pass filter and receives the coarse signal and a primary reference voltage signal, the active comparator generates the event signal.
    Type: Application
    Filed: January 15, 2019
    Publication date: July 16, 2020
    Inventors: Rakul VISWANATH, Nagesh SURENDRANATH, Sandeep Kesrimal OSWAL, Ratna Kumar Venkata PARUPUDI
  • Patent number: 10484636
    Abstract: An active pixel sensor a plurality of sensor pixels disposed in a row, a plurality of sensor pixels in a column, and steering circuitry coupled to each of the sensor pixels. Each of the sensor pixels includes a first pixel circuit, and a second pixel circuit. For each of the sensor pixels, the steering circuitry includes a first switch, a second switch, a third switch, and a fourth switch. The first switch and the second switch are connected in series to route an input signal to the first pixel circuit. The third switch and a fourth switch are connected in parallel to route the input signal to the second pixel circuit.
    Type: Grant
    Filed: March 20, 2018
    Date of Patent: November 19, 2019
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Sravana Kumar Goli, Jeevan Mithra, Nagesh Surendranath, Sandeep Kesrimal Oswal
  • Patent number: 10481283
    Abstract: A photon counting system includes a photon sensor, a charge-sensitive amplifier (CSA) and an analog-to-digital converter (ADC). The CSA is configured to convert photon energy detected by the photon sensor to voltage pulses. The ADC is configured to digitize the voltage pulses generated by the CSA. The ADC includes successive approximation circuitry. The successive approximation circuitry includes an N-bit digital-to-analog converter (DAC), an N-bit successive approximation register (SAR), a plurality of N-bit registers, and a multiplexer configured to selectively route outputs of the SAR and outputs of the N-bit registers to the DAC for conversion to an analog signal.
    Type: Grant
    Filed: November 6, 2018
    Date of Patent: November 19, 2019
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Rakul Viswanath, Nagesh Surendranath, Goli Sravana Kumar
  • Publication number: 20190297294
    Abstract: An active pixel sensor a plurality of sensor pixels disposed in a row, a plurality of sensor pixels in a column, and steering circuitry coupled to each of the sensor pixels. Each of the sensor pixels includes a first pixel circuit, and a second pixel circuit. For each of the sensor pixels, the steering circuitry includes a first switch, a second switch, a third switch, and a fourth switch. The first switch and the second switch are connected in series to route an input signal to the first pixel circuit. The third switch and a fourth switch are connected in parallel to route the input signal to the second pixel circuit.
    Type: Application
    Filed: March 20, 2018
    Publication date: September 26, 2019
    Inventors: Sravana Kumar GOLI, Jeevan MITHRA, Nagesh SURENDRANATH, Sandeep Kesrimal OSWAL
  • Publication number: 20190086561
    Abstract: A photon counting system includes a photon sensor, a charge-sensitive amplifier (CSA) and an analog-to-digital converter (ADC). The CSA is configured to convert photon energy detected by the photon sensor to voltage pulses. The ADC is configured to digitize the voltage pulses generated by the CSA. The ADC includes successive approximation circuitry. The successive approximation circuitry includes an N-bit digital-to-analog converter (DAC), an N-bit successive approximation register (SAR), a plurality of N-bit registers, and a multiplexer configured to selectively route outputs of the SAR and outputs of the N-bit registers to the DAC for conversion to an analog signal.
    Type: Application
    Filed: November 6, 2018
    Publication date: March 21, 2019
    Inventors: Rakul Viswanath, Nagesh Surendranath, Goli Sravana Kumar
  • Patent number: 10180351
    Abstract: A circuit includes a charge sensitive amplifier (CSA) that includes an input to receive current from a photon sensor and generates an output signal that represents photons received by the sensor and dark current of the sensor. A control circuit generates a compensation signal to offset the dark current from the photon sensor at the input of the CSA. The control circuit couples feedback from the CSA to enable the compensation signal if the photon current received from the sensor is below a predetermined threshold. The control circuit decouples the feedback from the CSA to disable the compensation signal if the photon current received from the sensor is above the predetermined threshold.
    Type: Grant
    Filed: December 8, 2016
    Date of Patent: January 15, 2019
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Rakul Viswanath, Nagesh Surendranath, Sandeep Kesrimal Oswal
  • Patent number: 10151845
    Abstract: A photon counting system includes a photon sensor, a charge-sensitive amplifier (CSA) and an analog-to-digital converter (ADC). The CSA is configured to convert photon energy detected by the photon sensor to voltage pulses. The ADC is configured to digitize the voltage pulses generated by the CSA. The ADC includes successive approximation circuitry. The successive approximation circuitry includes an N-bit digital-to-analog converter (DAC), an N-bit successive approximation register (SAR), a plurality of N-bit registers, and a multiplexer configured to selectively route outputs of the SAR and outputs of the N-bit registers to the DAC for conversion to an analog signal.
    Type: Grant
    Filed: August 2, 2017
    Date of Patent: December 11, 2018
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Rakul Viswanath, Nagesh Surendranath, Goli Sravana Kumar
  • Patent number: 10098595
    Abstract: The disclosure provides a circuit that includes a charge sensitive amplifier (CSA) that generates an integrated signal in response to a current signal. An active comparator is coupled to the CSA. The active comparator receives the integrated signal and a primary reference voltage signal, and generates an event detect signal. A first delay element is coupled to the active comparator and provides a fixed delay to the event detect signal to generate a convert signal. A discriminator system is coupled to the CSA. The discriminator system samples the integrated signal when activated by the convert signal.
    Type: Grant
    Filed: September 30, 2015
    Date of Patent: October 16, 2018
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Nagesh Surendranath, Rakul Viswanath, Sandeep Kesrimal Oswal
  • Patent number: 10060864
    Abstract: The disclosure provides a receiver with reduced noise. The receiver includes a photodiode that generates an input signal in response to received light pulses. A pixel switch is coupled to the photodiode. An operational amplifier is coupled to the photodiode through the pixel switch. A feedback capacitor and a reset switch are coupled between a first input port and an output port of the operational amplifier. A switched resistor network is coupled to the output port of the operational amplifier. A first switched capacitor network is coupled to the switched resistor network and samples a reset voltage. A second switched capacitor network is coupled to the switched resistor network and samples a signal voltage. A subtractor receives the reset voltage and the signal voltage, and generates a sample voltage. The second switched network comprises two or more capacitors.
    Type: Grant
    Filed: February 20, 2018
    Date of Patent: August 28, 2018
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Goli Sravana Kumar, Nagesh Surendranath
  • Patent number: 10024979
    Abstract: A photon counting system includes a photon sensor and pixel circuitry. The pixel circuitry includes a charge sensitive amplifier (CSA), an analog to digital converter (ADC), an event detector, and a coincidence detector. The CSA is configured to convert photon energy detected by the photon sensor to a voltage pulse. The ADC is coupled to an output of the CSA. The ADC is configured to digitize the voltage pulses generated by the CSA. The event detector is configured to determine whether output voltage of the CSA exceeds an event threshold voltage, and to trigger the ADC to digitize the output voltage based on the output voltage exceeding the event threshold voltage. The coincidence detector is configured to determine whether the output voltage of the CSA exceeds a coincidence threshold voltage, and to trigger the ADC to digitize the output voltage based on the output voltage exceeding the coincidence threshold voltage.
    Type: Grant
    Filed: November 1, 2017
    Date of Patent: July 17, 2018
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Rakul Viswanath, Nagesh Surendranath, Ratna Kumar Venkata Parupudi