National Semiconductor Corporation

Stuart H Urie

Jun Wan

Eric David Blom

Peter R Holloway

Harald Hieber

A data converter () for digitizing an analog input signal and providing digital output data at one or more conversion cycles includes a logic circuit () for generating a data conversion diagnostic bit () having first and second logical states. The data conversion diagnostic bit toggles from one logical state to the other logical state when a conversion cycle is completed and when the digital output data from the previous conversion cycle has been read. The data conversion diagnostic bit remains at the same logical state when no conversion cycle has been completed or when no reading of the digital output data has been carried out.

Data conversion diagnostic bit in a data converter

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 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 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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Milford, NH, United States of America

Stuart H Urie