Abstract: Various techniques to eliminate the error caused by variable ? coupled with a series resistance in BJTs are described. Multiple known currents are applied to a terminal of the BJT and a corresponding VBE is generated. A resistor R is coupled in series with a base or emitter of the BJT and an analog-to-digital converter (ADC) is used to measure the voltage across the resistor R for each of the known currents. These voltages are used to determine ratios of ? change, which are then used to determine a temperature of the BJT.

Abstract: Various techniques are described to accurately measure a ratio between the two currents supplied by a current source in a BJT temperature sensor. In an approach, a resistor is included between the current source and the emitter terminal of the BJT. An analog-to-digital converter (ADC) measures the voltage across the resistor R for each of the two currents. These voltages are used to determine current ratios, which are then used to determine a temperature of the BJT. The techniques are not limited to use with BJTs and are applicable to other semiconductor devices including diodes.

Abstract: A method and a circuit take a measurement of a sensor having first, second and third lead wires by: (a) providing first, second and third terminals for voltage measurements; (b) connecting a current sensing device (e.g., a reference resistor) to provide a signal at the third terminal that is indicative of the current in the third lead wire of the sensor; (c) connecting a first protective device between the first lead wire of the sensor and the first terminal; (d) connecting a second protective device between the second lead wire of the sensor and the second terminal; (e) connecting a first current source to the first lead wire of the sensor; (f) connecting a second current source to the second lead wire of the sensor; and (g) measuring a first voltage across the first and second terminals and a second voltage across the third terminal and the voltage reference.

Abstract: An integrated circuit includes (a) an analog-to-digital converter operated according to a first clock signal; and (b) a charge pump circuit providing a negative power supply voltage to the integrated circuit, the charge pump circuit being operated according to a second clock signal having a frequency that is different from a frequency of the first clock signal, such that a noise level introduced by the charge pump into the analog-to-digital converter is less than the average noise level over a predetermined range of frequencies for the second clock signal. The integrated circuit may further include a clock divider circuit (e.g., a programmable clock divider) that generates both the first clock signal and the second clock signal.

Abstract: A method and a circuit take a measurement of a sensor having first, second and third lead wires by: (a) providing first, second and third terminals for voltage measurements; (b) connecting a current sensing device (e.g., a reference resistor) to provide a signal at the third terminal that is indicative of the current in the third lead wire of the sensor; (c) connecting a first protective device between the first lead wire of the sensor and the first terminal; (d) connecting a second protective device between the second lead wire of the sensor and the second terminal; (e) connecting a first current source to the first lead wire of the sensor; (f) connecting a second current source to the second lead wire of the sensor; and (g) measuring a first voltage across the first and second terminals and a second voltage across the third terminal and the voltage reference.

Abstract: An integrated circuit includes (a) an analog-to-digital converter operated according to a first clock signal; and (b) a charge pump circuit providing a negative power supply voltage to the integrated circuit, the charge pump circuit being operated according to a second clock signal having a frequency that is different from a frequency of the first clock signal, such that a noise level introduced by the charge pump into the analog-to-digital converter is less than the average noise level over a predetermined range of frequencies for the second clock signal. The integrated circuit may further include a clock divider circuit (e.g., a programmable clock divider) that generates both the first clock signal and the second clock signal.

Abstract: A method for detecting an open-circuit in an external thermocouple network includes these steps: (a) injecting a current pulse of a predetermined duration into the external thermocouple network; and (b) measuring the voltage across the pair of terminals after a time period following the predetermined duration. In one example, the time period is sufficiently long to allow the current pulse to dissipate from the external thermocouple circuit when a thermocouple in the external thermocouple network does not have an open circuit. The thermocouple network may include a resistor-capacitor network provided between the thermocouple and one of the terminals.

Abstract: In a temperature sensing circuit, a method for measuring a resistance of a RTD device to sense temperature includes (a) connecting a first terminal of the RTD device to a first current source and connecting a second terminal of the RTD device to a second current source; (b) measuring a first voltage across the RTD device; (c) connecting the second terminal of the RTD device to the first current source and connecting the first terminal of the RTD device to the second current source; (d) measuring a second voltage across the RTD device; and (e) deriving the resistance of the RTD device based on the first voltage measurement and the second voltage measurement. The RTD device may be connected in series with a sense resistor to ground.

Abstract: Methods and systems for analog to digital converter and systems incorporating the same are provided. Specifically, an analog sampler that has a reduced input current is disclosed. According to the present teaching, an apparatus for sampling an input voltage includes a first switch having its first terminal connected to an input voltage, and a first pre-charging circuit, coupled to a second terminal of the first switch, that provides a first pre-charged voltage that is substantially equal to the input voltage. The first pre-charged voltage is provided at the first terminal of the first switch before the first switch is turned on. The apparatus further includes a second pre-charging circuit coupled to both the first pre-charging circuit and the second terminal of the first switch, where the second pre-charging circuit charges the first pre-charged voltage prior to the first switch being turned on.