Digital asic sensor platform

Abstract

The present invention relates to an optical sensor that may be implanted within a living animal (e.g., a human) and may be used to measure the concentration of an analyte in a medium within the animal. The optical sensor may wirelessly receive and may be capable of bi-directional data communication. The optical sensor may include a semiconductor substrate in which various circuit components, one or more photodectors and/or a light source may be fabricated. The circuit components fabricated in the semiconductor substrate may include a comparator, an analog to digital converter, a temperature transducer, a measurement controller, a rectifier and/or a nonvolatile storage medium. The comparator may output a signal indicative of the difference between the outputs of first and second photodetectors. The measurement controller may receive digitized temperature, photodetector and/or comparator measurements and generate measurement information, which may be wirelessly transmitted from the optical sensor.

What is claimed is: 
     
         1 . An optical sensor for implantation within a living animal and measurement of a concentration of an analyte in a medium within the living animal, the optical sensor comprising:
 indicator molecules having an optical characteristic responsive to the concentration of the analyte, the indicator molecules being configured to interact with the analyte in the medium within the living animal when the optical sensor is implanted within the living animal;   a semiconductor substrate;   a first photodetector mounted on or fabricated in the semiconductor substrate and configured to output a first analog light measurement signal indicative of the amount of light received by the first photodetector;   a second photodetector mounted on or fabricated in the semiconductor substrate and configured to output a second analog light measurement signal indicative of the amount of light received by the second photodetector, wherein the first and second photodetectors are symmetrically arranged relative to a center line running between the first and second photodetectors;   a light source configured to emit excitation light to the indicator molecules from an emission point aligned on the center line running between the first and second photodetectors;   a temperature transducer mounted on or fabricated in the semiconductor substrate and configured to output an analog temperature measurement signal indicative of a temperature of the optical sensor;   a comparator fabricated in the semiconductor substrate and configured to output an analog light difference measurement signal indicative of a difference between the first and second analog light measurement signals;   an analog to digital converter (ADC) fabricated in the semiconductor substrate and configured to convert (i) the analog temperature measurement signal to a digital temperature measurement signal, (ii) the first analog light measurement signal to a first digital light measurement signal, (iii) the second analog light measurement signal to a second digital light measurement signal and (iv) the analog light difference measurement signal to a digital light difference measurement signal;   an inductive element;   an input/output circuit fabricated in the semiconductor substrate and configured to wirelessly transmit via the inductive element measurement information and wirelessly receive via the inductive element a measurement command and power; and   a measurement controller fabricated in the semiconductor substrate and configured to:
 (i) in accordance with the measurement command, control the light source; 
 (ii) generate the measurement information in accordance with (a) the digital temperature measurement signal, (b) the first digital light measurement signal, (c) the second digital light measurement signal and (d) the digital light difference measurement signal; and 
 (iii) control the input/output circuit to wirelessly transmit the measurement information. 
   
     
     
         2 . The optical sensor of  claim 1 , wherein the optical sensor is a chemical or biochemical sensor. 
     
     
         3 . The optical sensor of  claim 1 , wherein the first and second photodetectors are fabricated in the semiconductor substrate. 
     
     
         4 . The optical sensor of  claim 3 , wherein the first and second photodetectors are photodiodes that have been monolithically formed in the semiconductor substrate using a complimentary metal oxide semiconductor (CMOS) process. 
     
     
         5 . The optical sensor of  claim 1 , further comprising light source mounting pads on the semiconductor substrate and configured such that the light source, when mounted on the light source mounting pads, has an emission point aligned on the center line running between the first and second photodetectors; and
 wherein the light source is mounted on the light source mounting pads.   
     
     
         6 . The optical sensor of  claim 1 , further comprising an isolation trough that electrically separates the first and second photodetectors. 
     
     
         7 . The optical sensor of  claim 1 , further comprising a nonvolatile storage medium fabricated in the semiconductor substrate. 
     
     
         8 . The optical sensor of  claim 7 , wherein the nonvolatile storage medium has stored therein measurement calibration information, and the measurement controller is configured to control the light source in accordance with the measurement command and the measurement calibration information. 
     
     
         9 . The optical sensor of  claim 7 , wherein the nonvolatile storage medium has stored therein identification information, the input/output circuit is configured to wirelessly transmit via the inductive element the identification information and the measurement controller is configured to control the input/output circuit to wirelessly transmit the identification information. 
     
     
         10 . The optical sensor of  claim 1 , wherein the temperature transducer is a band-gap based temperature transducer fabricated in the semiconductor substrate. 
     
     
         11 . The optical sensor of  claim 1 , wherein the comparator is a transimpedance amplifier. 
     
     
         12 . The optical sensor of  claim 1 , wherein the input/output circuit comprises a rectifier fabricated in the semiconductor substrate. 
     
     
         13 . The optical sensor of  claim 12 , wherein the rectifier is a Schottky diode. 
     
     
         14 . The optical sensor of  claim 1 , wherein the measurement information is digital measurement information. 
     
     
         15 . The optical sensor of  claim 1 , wherein the indicator molecules are signal channel indicator molecules, and the optical sensor further comprises reference channel indicator molecules configured to not interact with the analyte in the medium within the living animal when the optical sensor is implanted within the living animal;
 wherein the light source is configured to emit the excitation light to the signal channel indicator molecules and reference channel indicator molecules when turned on, the first photodetector is configured to receive excitation light emitted by the signal channel indicator molecules, and the second photodetector is configured to receive excitation light emitted by the reference channel indicator molecules.   
     
     
         16 . The optical sensor of  claim 1 , wherein the living animal is a living human being. 
     
     
         17 . The optical sensor of  claim 1 , wherein the medium is interstitial fluid. 
     
     
         18 . The optical sensor of  claim 17 , wherein the analyte is glucose. 
     
     
         19 . The optical sensor of  claim 17 , wherein the analyte is oxygen. 
     
     
         20 . The optical sensor of  claim 1 , wherein the medium is blood. 
     
     
         21 . The optical sensor of  claim 1 , wherein the indicator molecules are fluorescent indicator molecules. 
     
     
         22 . The optical sensor of  claim 1 , wherein the optical sensor has a size and shape that permits said sensor to be implanted within the living animal and wherein the measurement information is indicative of the concentration of the analyte in the medium within the living animal. 
     
     
         23 . The optical sensor of  claim 1 , wherein the inductive element comprises a coil. 
     
     
         24 . The optical sensor of  claim 1 , wherein the inductive element further comprises a ferrite core, and the coil is formed on the ferrite core. 
     
     
         25 . A sensor for implantation within a living animal and measurement of a concentration of an analyte in a medium within the living animal, the optical sensor comprising:
 indicator molecules having an optical characteristic responsive to the concentration of the analyte, the indicator molecules being configured to interact with the analyte in the medium within the living animal when the optical sensor is implanted within the living animal;   a semiconductor substrate;   a photodiode fabricated in the semiconductor substrate and configured to output an analog light measurement signal indicative of the amount of light received by the photodiode;   a light source configured to emit excitation light to the indicator molecules;   an analog to digital converter fabricated in the semiconductor substrate and configured to convert the analog light measurement signal to a digital light measurement signal;   an inductive element;   an input/output circuit fabricated in the semiconductor substrate and configured to wirelessly transmit via the inductive element measurement information and wirelessly receive via the inductive element a measurement command and power; and   a measurement controller fabricated in the semiconductor substrate and configured to:
 (i) in accordance with the measurement command, control the light source; 
 (ii) generate the measurement information in accordance with the digital light measurement signal; and 
 (iii) control the input/output circuit to wirelessly transmit the measurement information. 
   
     
     
         26 . The sensor of  claim 25 , wherein the photodiode has been monolithically formed in the semiconductor substrate using a complimentary metal oxide semiconductor (CMOS) process. 
     
     
         27 . The sensor of  claim 25 , further comprising light source mounting pads on the semiconductor substrate, wherein the light source is mounted on the light source mounting pads. 
     
     
         28 . The sensor of  claim 25 , further comprising a nonvolatile storage medium fabricated in the semiconductor substrate.