Some examples include a secure low-power sensor platform able to be used for activity monitoring or other purposes. For instance, a sensor system may sense sparse signals using compressed sensing. As one example, compressed sensing may be used to obtain sparse signals from analog sensor signals received from one or more sensors. The data obtained by compressed sensing may be sent subsequently to a computing device to reconstruct the sensor signal. Examples herein enable lower power usage, lower cost, and lower weight than conventional devices, while also enabling processing advantages, such as less overall data to process and lower data storage utilization.

An analog-to-digital converter (ADC) includes a comparator, a voltage reference circuit, a first capacitive digital-to-analog converter (CDAC), and a second CDAC. The first CDAC includes a plurality of capacitors. Each of the capacitors of the first CDAC includes a top plate coupled to a first input of the comparator, and a bottom plate switchably coupled to an output of the voltage reference circuit. The second CDAC includes a plurality of capacitors. Each of the capacitors of the second CDAC includes a top plate coupled to a second input of the comparator, and a bottom plate switchably coupled to a ground reference.

A digital to analog convertor comprises an output line; first, second and third pluralities of capacitors; and first and second bridge capacitors. The first plurality of capacitors is coupled in parallel with one another, coupled with the output line, and comprises a first least significant bit capacitor of a first capacitance value. The second plurality of capacitors is coupled in parallel with one another, coupled with the output line, and comprises a second capacitor of the first capacitance value. The third plurality of capacitors is coupled in parallel with one another, coupled with the output line, and comprises a third capacitor of the first capacitance value. The first bridge capacitor bridges the output line between the first plurality of capacitors and the second plurality of capacitors. The second bridge capacitor bridges the output line between the second plurality of capacitors and the third plurality of capacitors.

Disclosed examples include pipeline ADC, balancing circuits and methods to balance a load of a reference circuit to reduce non-linearity and settling effects for a reference voltage signal, in which balancing capacitors are connected to a voltage source in a pipeline stage ADC sample time period to precharge the balancing capacitors using a voltage above the reference voltage, and a selected set of the precharged balancing capacitors is connected to provide charge to the output of the reference circuit during the second time period.

A hybrid analog-to-digital converter (ADC) includes a plurality of analog-to-digital conversion circuits and a combining circuit. The analog-to-digital conversion circuits generate a plurality of partial digital outputs for a same analog input, respectively, wherein the analog-to-digital conversion circuits include a digital slope ADC used to perform signal quantization in a time domain. The combining circuit combines the partial digital outputs generated from the analog-to-digital conversion circuits to generate a final digital output of the analog input.

A Successive Approximation Register Analog-to-Digital Converter (SAR ADC) is disclosed. The SAR ADC includes a switched capacitor array, a buffer, a comparator and a control logic circuit. The switched capacitor array is arranged to sample an input signal according to a switch control signal to generate a sampling signal. The buffer is arranged to generate a common mode voltage. The comparator is arranged to receive the sampling signal and the common mode voltage in order to generate a comparison result. The control logic circuit is arranged to generate an output signal according to the comparison result, and generate the switch control signal to control the switched capacitor array. The control logic circuit further generates an operation control signal to adjust a Miller compensation capacitor inside the buffer. An associated control method is also disclosed.

In an example embodiment, an apparatus includes: a first sampling capacitor to switchably couple between an input analog voltage, a reference voltage (V.sub.REF) and a ground voltage; a second sampling capacitor to switchably couple between the reference voltage and the ground voltage; and a comparator having a first input terminal to couple to the first sampling capacitor and a second input terminal to couple to the second sampling capacitor. The comparator may be configured to compare a voltage level at the second input terminal to a sum voltage based at least in part on the input analog voltage to generate at least one bit of a digital output.

A two-capacitor digital-to-analog converter circuit having circuitry to compensate for an unwanted capacitance is disclosed. The converter is configured to generate an average voltage on two capacitors for a sequence of bits in a digital word so that when the final bit is reached, the average voltage corresponds to an analog level of the digital word. The converter is configured to input and average the voltage on the two capacitors using different modes to minimize the effects of capacitor mismatch and switching capacitance on the accuracy of the conversion. The converter includes a buffer amp that has an input capacitance that can affect the conversion. Accordingly, the converter further includes capacitance compensation circuitry configured to provide a replica input capacitance that can be charged and discharged according to the bits of the digital word and coupled to the input capacitor to prevent the input capacitance from affecting the conversion.

An analog-to-digital conversion circuit (100) is disclosed. It comprises a switched-capacitor SAR-ADC, (110) arranged to receive an analog input signal (x(t)) and a clock signal, to sample the analog input signal (x(t)), and to generate a sequence (W(n)) of digital output words corresponding to samples of the analog input signal (x(t)), wherein the SAR-ADC (110) is arranged to generate a bit of the digital output word per cycle of the clock signal. It further comprises a clock-signal generator (120) arranged to supply the clock signal to the SAR-ADC (110), and a post-processing unit (140) adapted to receive the sequence (W(n)) of digital output words and generate a sequence of digital output numbers (y(n)), corresponding to the digital output words, based on bit weights assigned to the bits of the digital output words. The bit weights are selected to compensate for a decay of a signal internally in the SAR-ADC (110).

A successive approximation register analog-to-digital converter includes a capacitance digital-to-analog converter (CDAC) having, a voltage storing circuit connected to an output terminal of the CDAC and including a plurality of capacitors connected in parallel, an output voltage of the CDAC being stored in a selected one of the capacitors, a selector configured to output a voltage stored in the selected one of the capacitors, a comparator configured to compare a voltage input to an input terminal thereof, which is connected to an output terminal of the CDAC, with a reference voltage, and a successive approximation register configured to control the CDAC based on an output of the comparator, and cyclically control the voltage storing circuit and the selector, such that the output of the selector is output to the output terminal one or more cycles after the output voltage was stored in the selected one of the capacitors.