System and method for converting analog values into digital form

Abstract

A method for converting analog values into digital form comprises comparing a current analog sample value with an analog input value to produce an outcome, generating a count value based on the outcome, the count value increasing upon successive like outcomes and being reset to an initial count value upon successive unlike outcomes, adding or subtracting the count value to/from a current digital sample value to generate a next digital sample value, the adding or subtracting being based on the outcome, and converting the next digital sample value to the current analog sample value.

1 . A method for converting analog values into digital form, said method comprising:
 sampling a first analog input value;   converting said first analog input value into a first digital value during a first time period;   sampling a second analog input value; and   converting said second analog input value into a second digital value during a second time period; and   wherein the duration of said second time period is different than the duration of said first time period.   
   
   
       2 . The method of  claim 1 , further comprising:
 sampling a third analog input value; and   converting said third analog input value into a third digital value during a third time period; and   wherein the duration of said third time period is different than the durations of said second time period and said first time period.   
   
   
       3 . The method of  claim 2 , wherein the duration between said step of sampling said first analog input value and said step of sampling said second analog input value is different than the duration between said step of sampling said second analog input value and said step of sampling said third analog input value. 
   
   
       4 . The method of  claim 3 , wherein:
 the duration between said step of sampling said first analog input value and said step of sampling said second analog input value depends on the duration of said first time period; and   the duration between said step of sampling said second analog input value and said step of sampling said third analog input value depends on the duration of said second time period.   
   
   
       5 . The method of  claim 4 , wherein:
 the duration of said first time period depends on the value of said first analog input value; and   the duration of said second time period depends on the value of said second analog input value.   
   
   
       6 . The method of  claim 1 , further comprising:
 outputting said first digital value; and   outputting said second digital value following said step of outputting of said first digital value.   
   
   
       7 . The method of  claim 6 , wherein the amount of time between said step of outputting said first digital value and said step of outputting said second digital value depends on the duration of at least one of said first time period and said second time period. 
   
   
       8 . The method of  claim 7 , wherein:
 the duration of said first time period depends on the value of said first analog input value; and   the duration of said second time period depends on the value of said second analog input value.   
   
   
       9 . The method of  claim 7 , wherein the amount of time between said step of outputting said first digital value and said step of outputting said second digital value is proportional to the difference between said first analog input value and said second analog input value. 
   
   
       10 . The method of  claim 9 , further comprising:
 sampling a third analog input value;   converting said third analog input value into a third digital value during a third time period; and   outputting said third digital value following said step outputting of said second digital value; and wherein   the duration of said third time period is different than the duration of said second time period and said first time period;   the time between said step of outputting said second digital value and said step of outputting said third digital value depends on the duration of at least one of said second time period and said third time period;   the duration of said second time period depends on the value of said second analog input value;   the duration of said third time period depends on the value of said third analog input value; and   the amount of time between said step of outputting said second digital value and said step of outputting said third digital value is proportional to the difference between said second analog input value and said third analog input value.   
   
   
       11 . The method of  claim 1 , further comprising:
 sequentially sampling a plurality of analog input values, each of analog input values sampled at an associated one of a plurality of sampling times;   converting each of said analog input values into a corresponding one of a plurality of digital values, each of said analog input values converted into said corresponding digital value during an associated one of a plurality of time periods;   sequentially outputting said plurality of digital values in a digital output stream; and   wherein said digital output stream incorporates timing information indicative of at least one of said plurality of sampling times and durations of said plurality of time periods.   
   
   
       12 . The method of  claim 11 , wherein said digital output stream incorporates timing information indicative of both of said plurality of sampling times and said durations of said plurality of time periods. 
   
   
       13 . The method of  claim 12 , wherein said duration of each of said plurality of time periods is indicative of a dithering time for an analog sample value to dither around said analog input value. 
   
   
       14 . The method of  claim 11 , wherein said digital output stream is a serial bit stream. 
   
   
       15 . The method of  claim 11 , wherein said digital output stream is a parallel bit stream. 
   
   
       16 . The method of  claim 1 , wherein the difference between the durations of said first time period and said second time period is proportional to the difference between said first analog input value and said second analog input value. 
   
   
       17 . A device for converting analog values into digital form, said device comprising:
 a sample-hold circuit operative to sample a first analog input value and to sample a second analog input value; and   conversion circuitry operative to convert said first analog input value into a first digital value during a first time period and to convert said second analog input value into a second digital value during a second time period; and   wherein the duration of said second time period is different than the duration of said first time period.   
   
   
       18 . The device of  claim 17 , wherein:
 said sample-hold circuit is further operative to sample a third analog input value; and   said conversion circuitry is further operative to convert said third analog input value into a third digital value during a third time period; and   wherein the duration of said third time period is different than the durations of said second time period and said first time period.   
   
   
       19 . The device of  claim 18 , wherein the duration between the times when said sample-hold circuit samples said first analog input value and said second analog input value is different than the duration between the times when said sample-hold circuit samples said second analog input value and said third analog input value. 
   
   
       20 . The device of  claim 19 , wherein:
 the duration between the times that said sample-hold circuit samples said first analog input value and said second analog input value depends on the duration of said first time period; and   the duration between the times that said sample-hold circuit samples said second analog input value and said third analog input value depends on the duration of said second time period.   
   
   
       21 . The device of  claim 20 , wherein:
 the duration of said first time period depends on the value of said first analog input value; and   the duration of said second time period depends on the value of said second analog input value.   
   
   
       22 . The device of  claim 17 , further comprising:
 an output terminal set; and   wherein said conversion circuitry is further operative to output said first digital value and said second digital value via said output terminal set, said second digital value being output after said first digital value.   
   
   
       23 . The device of  claim 22 , wherein the amount of time between when said conversion circuitry outputs said first digital value and said second digital value depends on the duration of at least one of said first time period and said second time period. 
   
   
       24 . The device of  claim 23 , wherein:
 the duration of said first time period depends on the value of said first analog input value; and   the duration of said second time period depends on the value of said second analog input value.   
   
   
       25 . The device of  claim 23 , wherein the amount of time between when said conversion circuitry outputs said first digital value and said second digital value is proportional to the difference between said first analog input value and said second analog input value. 
   
   
       26 . The device of  claim 25 , wherein:
 said sample-hold circuitry is operative to sample a third analog input value;   said conversion circuitry is operative to convert said third analog input value into a third digital value during a third time period;   said conversion circuitry is operative to output said third digital value on said output terminal set following said step outputting of said second digital value;   the duration of said third time period is different than the duration of said second time period and said first time period;   the time between when said conversion circuitry outputs said second digital value and said third digital value depends on the duration of at least one of said second time period and said third time period;   the duration of said second time period depends on the value of said second analog input value;   the duration of said third time period depends on the value of said third analog input value; and   the amount of time between when said conversion circuitry outputs said second digital value and said third digital value is proportional to the difference between said second analog input value and said third analog input value.   
   
   
       27 . The device of  claim 17 , wherein:
 said sample-hold circuit is operative to sequentially sample a plurality of analog input values, said sample-hold circuit sampling each of analog input values at an associated one of a plurality of sampling times;   said conversion circuitry is operative to convert each of said analog input values into a corresponding one of a plurality of digital values, said conversion circuitry converting each of said analog input values into said corresponding digital value during an associated one of a plurality of time periods;   said conversion circuitry is operative to sequentially output said plurality of digital values in a digital output stream; and   wherein said digital output stream incorporates timing information indicative of at least one of said plurality of sampling times and durations of said plurality of time periods.   
   
   
       28 . The device of  claim 27 , wherein said digital output stream incorporates timing information indicative of both of said plurality of sampling times and said durations of said plurality of time periods. 
   
   
       29 . The device of  claim 28 , wherein said duration of each of said plurality of time periods is indicative of a dithering time for an analog sample value to dither around said analog input value. 
   
   
       30 . The device of  claim 27 , wherein said digital output stream is a serial bit stream. 
   
   
       31 . The device of  claim 27 , wherein said digital output stream is a parallel bit stream. 
   
   
       32 . The device of  claim 17 , wherein the difference between the durations of said first time period and said second time period is proportional to the difference between said first analog input value and said second analog input value. 
   
   
       33 . A device for converting analog values into digital form, said device comprising:
 a sample-hold circuit operative to sequentially sample a plurality of analog input values;   means for converting each of said analog input values into a corresponding one of a plurality of digital values, said means for converting operative to vary the conversion rate between different ones of said analog input values; and   means for outputting said plurality of digital values as a digital output stream.   
   
   
       34 . A method for converting analog values into digital form, said method comprising:
 comparing a current analog sample value with an analog input value to produce an outcome;   generating a count value based on the outcome and successive outcomes, the count value increasing upon successive like outcomes and being reset to an initial count value upon successive unlike outcomes;   adding or subtracting the count value to/from a current digital sample value to generate a next digital sample value, the adding or subtracting being based on the outcome;   converting the next digital sample value to the current analog sample value; and   repeating the steps of comparing, generating, adding or subtracting, and converting until the current analog sample value reaches a dithering state around the analog input value.   
   
   
       35 . A method for converting analog values into digital form, said method comprising:
 comparing a current analog sample value with an analog input value to produce an outcome;   generating a count value based on the outcome and successive outcomes, the count value increasing upon successive like outcomes and being reset to an initial count value upon successive unlike outcomes;   adding or subtracting the count value to/from a current digital sample value to generate a next digital sample value, the adding or subtracting being based on the outcome; and   converting the next digital sample value to the current analog sample value; and   wherein the count value is generated based on at least one function selected from the group consisting of a constant function, a linear function, an exponential function, a logarithmic function, and any combination thereof.   
   
   
       36 . A device for converting analog values into digital form, said device comprising:
 a comparator for comparing a current analog sample value with an analog input value to produce an outcome;   a count generator for generating a count value based on the outcome and successive outcomes, the count value increasing upon successive like outcomes and being reset to an initial count value upon successive unlike outcomes;   a digital accumulator for receiving the count value and for adding or subtracting the count value to/from a current digital sample value to generate a next digital sample value, the adding or subtracting being based on the outcome;   a digital-to-analog converter for converting the next digital sample value to the current analog sample value; and   a control circuit for determining when at least three successive unlike outcomes have occurred, thereby determining that a dithering state around the analog input value has been reached.   
   
   
       37 . A device for converting analog values into digital form, said device comprising:
 a comparator for comparing a current analog sample value with an analog input value to produce an outcome;   a count generator for generating a count value based on the outcome and successive outcomes, the count value increasing upon successive like outcomes and being reset to an initial count value upon successive unlike outcomes;   a digital accumulator for receiving the count value and for adding or subtracting the count value to/from a current digital sample value to generate a next digital sample value, the adding or subtracting being based on the outcome; and   a digital-to-analog converter for converting the next digital sample value to the current analog sample value; and   wherein the device is configured for encoding a stream of current analog sample values into a serial bit stream.