Abstract: A buffer amplifier has a power on state and a sleep state. During regular operation a coupling state of a load to an output node is detected using feedback voltage. In a sleep mode and in a power collapse mode a detection current is injected into the output node, to produce a voltage, and the coupling state of the load is detected from the voltage. Optionally, the detection current and detecting of the voltage on the output node is enables by a low duty cycle clock. Optionally, signals generated in detecting the coupling state are qualified through a debounce circuit.

Abstract: A buffer amplifier has a power on state and a sleep state. During regular operation a coupling state of a load to an output node is detected using feedback voltage. In a sleep mode and in a power collapse mode a detection current is injected into the output node, to produce a voltage, and the coupling state of the load is detected from the voltage. Optionally, the detection current and detecting of the voltage on the output node is enables by a low duty cycle clock. Optionally, signals generated in detecting the coupling state are qualified through a debounce circuit.

Abstract: Embodiments of capacitive sensors (500, 600) and methods for reducing noise in capacitive sensors are provided. Embodiments of capacitive sensors include a gain stage (510, 610), a capacitive sensor output, and an active filtered-sampling stage (550, 650). The an active filtered-sampling stage includes a first resistive element (555, 655) coupled to the gain stage output, a second resistive element (565, 670) coupled to the capacitive sensor output, a node (560, 660) between the first and second resistive elements, and a switch (575, 675) selectively coupling the first node to an integrator circuit (550, 650), where the integrator circuit is coupled to the capacitive sensor output.

Abstract: A sensor system (20) includes transducers (32, 34) each yielding an analog signal (37, 39) representing a parameter independently sensed by each of the transducers (32, 34). The signals (37, 39) are summed and the resulting transducer signal (46) is converted to a digital transducer signal (26) by a high resolution analog-to-digital converter (ADC) (48). Concurrently, one of the signals (37, 39) is subtracted from the other. The resulting difference signal (56) is converted to a digital difference signal (60) by a low resolution ADC (58). When the digital difference signal (60) is within a threshold window (78), a fault signal (28) indicates a normal condition (80) of the transducers (32, 34). When the signal (60) falls outside of the threshold window (78), a fault signal (28) indicates a fault condition (82) of the transducers. The transducer and fault signals (26, 28) are concurrently output from the sensor system (20).

Abstract: Embodiments of capacitive sensors (500, 600) and methods for reducing noise in capacitive sensors are provided. Embodiments of capacitive sensors include a gain stage (510, 610), a capacitive sensor output, and an active filtered-sampling stage (550, 650). The an active filtered-sampling stage includes a first resistive element (555, 655) coupled to the gain stage output, a second resistive element (565, 670) coupled to the capacitive sensor output, a node (560, 660) between the first and second resistive elements, and a switch (575, 675) selectively coupling the first node to an integrator circuit (550, 650), where the integrator circuit is coupled to the capacitive sensor output.

Abstract: An apparatus and method are provided for reducing noise in a capacitive sensor (200). One apparatus includes a gain stage (210) including an output, the gain stage configured to generate a first signal having a noise component and a second signal having a desired output component and the noise component, and a filtered-sampling stage (250) having an input coupled to the gain stage output, the filtered-sampling stage configured to sample the first signal, store the first signal, and subtract the first signal from the second signal to produce a desired output signal. A method includes generating a first signal having a first noise component of the gain stage (710), storing the first signal (725), generating a second signal comprising a desired output component and the first noise component (730), and subtracting the first signal from the second signal to produce a first output signal having the desired output component (750).

Abstract: A sensor system (20) includes transducers (32, 34) each yielding an analog signal (37, 39) representing a parameter independently sensed by each of the transducers (32, 34). The signals (37, 39) are summed and the resulting transducer signal (46) is converted to a digital transducer signal (26) by a high resolution analog-to-digital converter (ADC) (48). Concurrently, one of the signals (37, 39) is subtracted from the other. The resulting difference signal (56) is converted to a digital difference signal (60) by a low resolution ADC (58). When the digital difference signal (60) is within a threshold window (78), a fault signal (28) indicates a normal condition (80) of the transducers (32, 34). When the signal (60) falls outside of the threshold window (78), a fault signal (28) indicates a fault condition (82) of the transducers. The transducer and fault signals (26, 28) are concurrently output from the sensor system (20).

Abstract: An apparatus and method are provided for reducing noise in a capacitive sensor (200). One apparatus includes a gain stage (210) including an output, the gain stage configured to generate a first signal having a noise component and a second signal having a desired output component and the noise component, and a filtered-sampling stage (250) having an input coupled to the gain stage output, the filtered-sampling stage configured to sample the first signal, store the first signal, and subtract the first signal from the second signal to produce a desired output signal. A method includes generating a first signal having a first noise component of the gain stage (710), storing the first signal (725), generating a second signal comprising a desired output component and the first noise component (730), and subtracting the first signal from the second signal to produce a first output signal having the desired output component (750).