National Semiconductor Corporation

Ixys Corporation

Teradyne, Inc.

Littelfuse, Inc.

Other

Eric David Blom

Jun Wan

Peter R Holloway

Stuart H Urie

James F Anderson

Ronald A Sartschev

Ernest P Walker

Anatoliy V Tsyrganovich

Allan M Ryan

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

Self-oscillating spread spectrum frequency control loop

A programmable temperature compensated voltage reference is disclosed. In an exemplary embodiment, an apparatus includes a digital-to-analog converter (DAC) that uses a reference voltage and a code to generate a DAC output voltage. The apparatus also includes a temperature compensator that uses a temperature measurement (T) and the DAC code to generate a temperature compensation signal. The temperature compensation signal is represented by a third order polynomial equation. The apparatus also includes a signal combiner that combines the DAC output voltage and the temperature compensation signal to generate a temperature compensated programmable reference voltage.

Programmable temperature compensated voltage generator

A chopper stabilzed amplifier with synchronous switched capacitor noise filtering is disclosed. In an exemplary embodiment, an apparatus includes a chopper amplifier having an input that receives an input signal and an output that outputs an amplified signal. The chopper amplifier includes an input chopping circuit and an output chopping circuit, where the input and output chopping circuits operate in response to a chop clock. The apparatus also includes a switched capacitor filter having an input that receives the amplified signal and an output that outputs a filtered signal. The switched capacitor filter operates in response to a filter clock. The apparatus also includes a filter timing adjuster that receives a reference voltage and adjusts a phase of the filter clock with respect to the chop clock to reduce chopper noise on that reference voltage.

Chopper stabilized amplifier with synchronous switched capacitor noise filtering

A chopper stabilized amplifier with synchronous switched capacitor noise filtering is disclosed. In an exemplary embodiment, an apparatus includes a chopper amplifier having an input that receives an input signal and an output that outputs an amplified signal. The chopper amplifier includes an input chopping circuit and an output chopping circuit, where the input and output chopping circuits operate in response to a chop clock. The apparatus also includes a switched capacitor filter having an input that receives the amplified signal and an output that outputs a filtered signal. The switched capacitor filter operates in response to a filter clock. The apparatus also includes a filter timing adjuster that receives a reference voltage and adjusts a phase of the filter clock with respect to the chop clock to reduce chopper noise on that reference voltage.

A semi-passive radio frequency identification (RFID) tag being coupled to a battery providing a battery voltage for powering a part of the circuitry of the RFID tag includes an RF communication block receiving and transmitting RF signals, a sensor block including a frequency ratio digitizing temperature sensor for alternately measuring the ambient temperature and the battery voltage, and a control logic block in communication with the RF communication block and the sensor block. The control logic controls the operation of the RF communication block and the sensor block and stores temperature and voltage measurement data generated by the sensor block. In one embodiment, the control logic block of the RFID tag operates based on a system clock and the sensor block provides a reference clock to the control logic block for use in calibrating the system clock of the control logic block.

RFID temperature logger incorporating a frequency ratio digitizing temperature sensor

A digitizing ohmmeter system for providing a digital resistance ratio measurement includes a high impedance current source providing a DC excitation current to an impedance-varying input sensor and a reference resistor and an ADC circuit including a charge-balancing modulator and a digital post processing circuit. The same DC excitation current passes through both the input sensor and the reference resistor. The system utilizes a switched capacitor input stage to sample the voltage across the input sensor and the voltage across the reference resistor to generate an input voltage step and a reference voltage step which are coupled to the modulator of the ADC circuit. The digitizing ohmmeter system thereby realizes fully ratiometric operation such that neither a precise current source nor a precise voltage source is required for accurate resistance ratio measurements and only a stable known reference resistor is necessary for accurate absolute resistance measurements.

Resistance ratio digitizing ohmmeter system

A frequency ratio digitizing temperature sensor for generating a linearity-corrected temperature output signal includes an input generation circuit receiving a PTAT current and a CTAT current and a frequency ratio ADC including data and reference oscillators. The input generation circuit generates a first current from the weighted sum of the PTAT current and the CTAT current and also generates a first corrected current being the sum of the first current and a first portion of the PTAT current. The input generation circuit provides a first output current indicative of the PTAT current and a first output voltage generated by applying the first corrected current to a first resistor for use with the data oscillator and provides a second output current being the first corrected current and a second output voltage generated by applying the first current to a second resistor for use with the reference oscillator of the ADC.

Frequency ratio digitizing temperature sensor with linearity correction

A tri-level decoder circuit includes a first decoder circuit and a second decoder circuit. The first decoder circuit is configured to compare an input voltage to a first threshold, and the second decoder circuit is configured to compare the input voltage to a second threshold. The first decoder circuit is configured to provide substantially no current to a current mirror if the input voltage is less than the first threshold, and to provide a current to the current mirror otherwise. The current mirror is configured to reflect the current to provide a reflected current. A current source is configured to pull down a first output node to a first logic level if the reflected current is substantially zero. The current mirror is configured to drive the first output node to a second logic level otherwise. The second decoder circuit may operate similarly.

Low power tri-level decoder circuit

A digitizing temperature measurement system for providing a digital temperature measurement includes an excitation source for providing switched excitation currents to two or three temperature sensing elements and an ADC circuit including a charge-balancing modulator and a digital post processing circuit. The system utilizes synchronous AC excitation of the temperature sensing elements and an AC coupled analog-to-digital converter input. The temperature measurement system also implements correlated double sampling for noise cancellation to provide low noise and highly accurate analog-to-digital conversions. The modulator receives a charge domain reference signal generated by a reference charge packet generator incorporating a charge based bandgap subsystem. Therefore, the temperature measurement system can be operated at very low supply voltages, such as 1.0 Vdc. A low noise and highly accurate temperature measurement system is thus realized where temperature measurements of very high resolutions (up to 16 bit) can be attained.

Digitizing temperature measurement system and method of operation

A digitizing ohmmeter system for providing a digital resistance measurement includes a current source for providing an excitation current to an impedance-varying input sensor and an ADC circuit including a charge-balancing modulator and a digital post processing circuit. The system utilizes synchronous AC excitation of the input sensor and an AC coupled analog-to-digital converter input. The digitizing ohmmeter system also implements correlated double sampling for noise cancellation to provide low noise and highly accurate analog-to-digital conversions. The ADC circuit includes a reference signal generator generating a resistance reference signal by time-sharing the excitation current with the input sensor. The digitizing ohmmeter system thereby realizes fully ratiometric operation such that neither a precise current source nor a precise voltage source is required for accurate resistance measurements.

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Wakefield, MA, United States of America

Eric David Blom