Abstract: A closed-loop heater control circuit for use with integrated circuit thermal sensing devices, such as thermal accelerometers, is disclosed. The heater control circuit includes a switched-capacitor integrating circuit and a controller or modulator. The switched-capacitor integrating unit integrates a common-mode voltage signal from an instrument amplifier with respect to an analog common reference voltage. In operation, the switched-capacitor integrating unit is adapted so that the closed-loop is opened briefly at the beginning of every new cycle, e.g., using an enable signal, during fast start-up or power-down.

Abstract: A system, device, and method for minimizing x-axis and/or y-axis offset shift due to internally produced as well as externally produced on chip temperature imbalances. At least one temperature gradient canceling device is disposed on a substrate including a temperature gradient sensitive device having at least one pair of sensors. Voltage signals generated by the temperature gradient canceling devices can be combined with voltage signals generated by each of the pair of sensors to account for the offset.

Abstract: A closed-loop heater control circuit for use with integrated circuit thermal sensing devices, such as thermal accelerometers, is disclosed. The heater control circuit includes a switched-capacitor integrating circuit and a controller or modulator. The switched-capacitor integrating unit integrates a common-mode voltage signal from an instrument amplifier with respect to an analog common reference voltage. In operation, the switched-capacitor integrating unit is adapted so that the closed-loop is opened briefly at the beginning of every new cycle, e.g., using an enable signal, during fast start-up or power-down.

Abstract: Single chip 3-axis thermal accelerometer devices include a substrate, at least one cavity etched in the substrate, a fluid disposed in the cavity, a bridge structure suspended over an opening of the cavity, and a plurality of heater elements and temperature sensing elements disposed on the bridge structure. The substrate has a substantially planar surface defined by X and Y coordinate axes, and the bridge structure is suspended over the opening of the cavity in the X-Y plane. In one embodiment, the bridge structure is configured to position at least two of the temperature sensing elements out of the X-Y plane. The heater and temperature sensing elements are disposed on the bridge structure in optimized arrangements for providing reduced temperature coefficients and for producing output voltages having reduced DC offset and drift.

Abstract: A thermal accelerometer device that allows up to three axes of acceleration sensing. The thermal accelerometer includes a substantially planar substrate, a cavity formed in the substrate, a heater element, and at least first and second temperature sensing elements. The heater element is suspended over the cavity, and the first and second temperature sensing elements are disposed along the X or Y axis in the substrate plane on opposite sides of and at equal distances from the heater element. The thermal accelerometer employs differential temperatures detected by the temperature sensing elements to provide indications of acceleration in the X or Y directions. Further, the thermal accelerometer employs a common mode temperature detected by the temperature sensing elements to provide an indication of acceleration along a Z axis perpendicular to the X and Y axes.

Abstract: A thermal accelerometer device that provides a compensation for sensitivity variations over temperature. The thermal accelerometer includes signal conditioning circuitry operative to receive analog signals representing a differential temperature is indicative of a sensed acceleration. The signal conditioning circuitry includes serially connected A-to-D and D-to-A converters, which implement a temperature dependent function and process the received signals to provide a compensation for sensitivity variations over a range of ambient temperature. To provide a ratiometric compensation for variations in power supply voltage, a buffered voltage proportional to the supply voltage is provided as a reference voltage to the D-to-A converter. The thermal accelerometer includes a self-test circuit for verifying the integrity of a heater, temperature sensors, and circuitry included within the device.

Abstract: Single chip 3-axis thermal accelerometer devices include a substrate, at least one cavity etched in the substrate, a fluid disposed in the cavity, a bridge structure suspended over an opening of the cavity, and a plurality of heater elements and temperature sensing elements disposed on the bridge structure. The substrate has a substantially planar surface defined by X and Y coordinate axes, and the bridge structure is suspended over the opening of the cavity in the X-Y plane. In one embodiment, the bridge structure is configured to position at least two of the temperature sensing elements out of the X-Y plane. The heater and temperature sensing elements are disposed on the bridge structure in optimized arrangements for providing reduced temperature coefficients and for producing output voltages having reduced DC offset and drift.

Abstract: A thermal accelerometer device that allows up to three axes of acceleration sensing. The thermal accelerometer includes a substantially planar substrate, a cavity formed in the substrate, a heater element, and at least first and second temperature sensing elements. The heater element is suspended over the cavity, and the first and second temperature sensing elements are disposed along the X or Y axis in the substrate plane on opposite sides of and at equal distances from the heater element. The thermal accelerometer employs differential temperatures detected by the temperature sensing elements to provide indications of acceleration in the X or Y directions. Further, the thermal accelerometer employs a common mode temperature detected by the temperature sensing elements to provide an indication of acceleration along a Z axis perpendicular to the X and Y axes.

Abstract: A thermal accelerometer device that provides a compensation for sensitivity variations over temperature. The thermal accelerometer includes signal conditioning circuitry operative to receive analog signals representing a differential temperature is indicative of a sensed acceleration. The signal conditioning circuitry includes serially connected A-to-D and D-to-A converters, which implement a temperature dependent function and process the received signals to provide a compensation for sensitivity variations over a range of ambient temperature. To provide a ratiometric compensation for variations in power supply voltage, a buffered voltage proportional to the supply voltage is provided as a reference voltage to the D-to-A converter. The thermal accelerometer includes a self-test circuit for verifying the integrity of a heater, temperature sensors, and circuitry included within the device.