A low power current-to-frequency converter circuit provides an output frequency signal FOUT having a frequency that varies as a function of a low level analog input current signal. The analog input current signal is typically generated by an implantable sensor element, designed to sense a particular substance or parameter within body tissue or fluids to which the sensor is exposed, with the magnitude of the analog signal providing a measure of the sensed substance or parameter. Conversion of the low level analog current to the output frequency signal facilitates transmission of the data signal over a shared data bus and other digital processing of the data signal. The current-to-frequency converter circuit is fabricated from low power FET-based integrated circuits, and includes an operational amplifier having its positive input terminal connected to a storage capacitor that is charged by the analog input current signal, a voltage-controlled oscillator driven by the charge (voltage) on the storage capacitor that produces the output frequency signal, and a charge pump circuit that pumps a discrete amount of charge off of the storage capacitor during each cycle of the output frequency signal.

Low power current-to-frequency converter circuit for use in implantable sensors

An implantable sensor includes electronic circuitry for automatically performing on a periodic basis, e.g., every 1 to 24 hours, specified integrity tests which verify proper operation of the sensor.

Implantable sensor and integrity tests therefor

A controller for a power supply includes a logic block and a time-to-frequency converter. The logic block is to generate a drive signal in response to a clock signal. The drive signal is to be coupled to control switching of a power switch of the power supply to regulate an output of the power supply. The time-to-frequency converter is coupled to the logic block and generates the clock signal having a frequency responsive to a time period of the drive signal.

Power supply controller with input voltage compensation for efficiency and maximum power output

A highly accurate system to measure the level of material in a vessel. A probe is provided in the vessel. The vessel and the probe are at different potentials so as to create a capacitance therebetween. The air and materials in the vessel act as dielectrics. As the material level varies, so does the capacitance. This capacitance is subjected to a charge-discharge-charge cycle yielding integrated net neutral charge. The duration of the cycle is compared to a reference time to determine capacitance, which is proportional to the level of material in the vessel.

Apparatus and method for sensing material level by capacitance measurement

A VCO (110) can be configured to convert an analog input signal (105) to a digital output signal (125). In accordance with the inventive arrangements, the VCO can convert the analog input signal to at least one intermediate signal (130) having a frequency dependent on the analog input signal. A frequency detector (115) can be configured to determine a frequency of at least one intermediate signal. Subsequently, a mapping circuit (120) can be configured to map the determined frequency of the at least one intermediate signal to an output value representing the digital output signal (125).

Method and system for VCO-based analog-to-digital conversion (ADC)

A bipolar analog voltage is converted into a digital signal by sensing the polarity of the voltage and selectively supplying a bias voltage to an analog-to-digital converter, which can preferably be a charge balanced voltage to frequency converter, as a function of the sensed polarity. The voltage to frequency converter has a double valued variable frequency output with a discontinuity at zero volt such that the converter derives a maximum output frequency for a maximum positive voltage and also for a negative value slightly displaced from zero; the voltage to the frequency converter minimum output frequency is derived from positive voltages slightly greater than zero and for maximum negative voltages. The converter output frequency and the sensed polarity are supplied to a frequency to digital converter which derives an output signal having a bit representing the polarity of the analog voltage and additional bits indicative of the magnitude of the analog voltage.

Analog to digital conversion with charge balanced voltage to frequency converter having polarity responsive offset

OF THE DISCLOSURE A bipolar analog voltage is converted into a digital signal by sensing the polarity of the voltage and selectively supplying a bias voltage to an analog-to-digital converter, which can preferably be a charge balanced voltage to frequency converter, as a function of the sensed polarity. The voltage to frequency converter has a double valued variable frequency output with a discontinuity at zero volt such that the converter derives a maximum output frequency for a maximum positive voltage and also for a negative value slightly displaced from zero; the voltage to the frequency converter minimum output frequency is derived from positive voltages slightly greater than zero and for maximum negative voltages. The converter output frequency and the sensed polarity are supplied to a frequency to digital converter which derives an output signal having a bit representing the polarity of the analog voltage and additional bits indicative of the magnitude of the analog voltage.

Paul R. Lantz

Papers

Analog to digital conversion with charge balanced voltage to frequency converter having polarity responsive offset

Bipolar voltage to frequency converter