Abstract: A system may comprise: an excitation current source; a first electrode coupled to the excitation current source; and a second electrode coupled to the excitation current source. The first and second electrodes may be configured to pass an excitation current from the excitation current source through a human body. First and second calibration resistors may be coupled to and positioned between the excitation current source and the first electrode. Third and fourth calibration resistors may be coupled to and positioned between the excitation current source and the second electrode. The system may also comprise a sensor configured to measure voltages across each of the first, second, third, and fourth calibration resistors.

Abstract: A bio-sensing device (and method) calibrates a time period used to make bio-physical measurements. The device initiates a light source sense phase followed by a first ambient sense phase and a second ambient sense phase. In the light source sense phase, the device is configured to receive a digital value indicative of current through a photodetector while the light source circuit is enabled and in each of the first and second ambient sense phases, the device is configured to receive digital values while the light source circuit is disabled. The device iteratively varies the time period between the phases until the digital value received during the first ambient sense phase is within a threshold of the digital value received during the second ambient sense phase. It then applies the same time separation between the light source sense phase and the ambient phase thereby equalizing the magnitude of the ambient light in the two phases.

Abstract: At least some embodiments are directed to a light detection system comprising a photodiode, a transimpedance amplifier (TIA) having a differential output and a differential input coupled across the photodiode, a first bias current source coupled to an anode of the photodiode, and a second bias current source coupled to a cathode of the photodiode. The system also comprises a dynamic control logic coupled to the first and second bias current sources and configured to vary bias currents provided by the first and second bias current sources based on the differential output such that the photodiode is reverse-biased.

Abstract: The disclosure provides a circuit for impedance measurement. The circuit includes an excitation source coupled between a first set of input switches. An impedance network is coupled between the first set of input switches and a first set of output switches. The impedance network includes a body impedance and a plurality of electrode impedances. A sense circuit is coupled to the first set of output switches. The sense circuit measures the body impedance and at least one electrode impedance of the plurality of electrode impedances.

Abstract: The disclosure provides a circuit for impedance measurement. The circuit includes an excitation source coupled between a first set of input switches. An impedance network is coupled between the first set of input switches and a first set of output switches. The impedance network includes a body impedance and a plurality of electrode impedances. A sense circuit is coupled to the first set of output switches. The sense circuit measures the body impedance and at least one electrode impedance of the plurality of electrode impedances.

Abstract: The disclosure provides a circuit for impedance measurement. The circuit includes an excitation source that generates an excitation signal. A switched resistor network is coupled to the excitation source, and generates an output signal in response to the excitation signal. A sense circuit is coupled to the switched resistor network, and generates a sense signal in response to the output signal. A comparator is coupled to the sense circuit, and generates a clock signal in response to the sense signal. A mixer is coupled to the sense circuit, and multiplies the sense signal and the clock signal to generate a rectified signal. A low pass filter is coupled to the mixer and filters the rectified signal to generate an averaged signal. A processor is coupled to the low pass filter and measures a body impedance from the averaged signal.

Abstract: At least some embodiments are directed to a light detection system comprising a photodiode, a transimpedance amplifier (TIA) having a differential output and a differential input coupled across the photodiode, a first bias current source coupled to an anode of the photodiode, and a second bias current source coupled to a cathode of the photodiode. The system also comprises a dynamic control logic coupled to the first and second bias current sources and configured to vary bias currents provided by the first and second bias current sources based on the differential output such that the photodiode is reverse-biased.

Abstract: A system may comprise: an excitation current source; a first electrode coupled to the excitation current source; and a second electrode coupled to the excitation current source. The first and second electrodes may be configured to pass an excitation current from the excitation current source through a human body. First and second calibration resistors may be coupled to and positioned between the excitation current source and the first electrode. Third and fourth calibration resistors may be coupled to and positioned between the excitation current source and the second electrode. The system may also comprise a sensor configured to measure voltages across each of the first, second, third, and fourth calibration resistors.

Abstract: A bio-sensing device (and method) calibrates a time period used to make bio-physical measurements. The device initiates a light source sense phase followed by a first ambient sense phase and a second ambient sense phase. In the light source sense phase, the device is configured to receive a digital value indicative of current through a photodetector while the light source circuit is enabled and in each of the first and second ambient sense phases, the device is configured to receive digital values while the light source circuit is disabled. The device iteratively varies the time period between the phases until the digital value received during the first ambient sense phase is within a threshold of the digital value received during the second ambient sense phase. It then applies the same time separation between the light source sense phase and the ambient phase thereby equalizing the magnitude of the ambient light in the two phases.

Abstract: The disclosure provides a circuit for impedance measurement. The circuit includes an excitation source that generates an excitation signal. A switched resistor network is coupled to the excitation source, and generates an output signal in response to the excitation signal. A sense circuit is coupled to the switched resistor network, and generates a sense signal in response to the output signal. A comparator is coupled to the sense circuit, and generates a clock signal in response to the sense signal. A mixer is coupled to the sense circuit, and multiplies the sense signal and the clock signal to generate a rectified signal. A low pass filter is coupled to the mixer and filters the rectified signal to generate an averaged signal. A processor is coupled to the low pass filter and measures a body impedance from the averaged signal.

Abstract: The disclosure provides a circuit for impedance measurement. The circuit includes an excitation source coupled between a first set of input switches. An impedance network is coupled between the first set of input switches and a first set of output switches. The impedance network includes a body impedance and a plurality of electrode impedances. A sense circuit is coupled to the first set of output switches. The sense circuit measures the body impedance and at least one electrode impedance of the plurality of electrode impedances.