Integrating analog to digital converter having offset error compensation
AssigneeTokyo Shibaura Denki Kabushiki Kaisha
InventorsEiji Masuda, Yasoji Suzuki
Life of this patent
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Abstract
An integrating analog to digital converter having a switching circuit for selecting any one of an analog input voltage, a first reference voltage, or an analog ground voltage; an intermediate voltage selected by the switching circuit and the intermediate voltage generated by the intermediate voltage generating circuit; and a comparator for producing a signal to control the operation of the switching circuit and the voltage level produced by the intermediate voltage generating circuit according to the results of a comparison between the output signal from the integration circuit and a second reference voltage.
Claims10
A method of converting an analog signal into a digital signal comprising the steps of:
- providing an integrating circuit having first and second input terminals adapted to receive voltage signals, said integrating circuit for integrating the difference in voltage level between the voltage signals provided to said first and second input terminals to produce an integrating output signal including a voltage offset component;
- supplying a first reference voltage level at a first reference voltage terminal;
- supplying a second reference voltage level at a second reference voltage terminal;
- supplying an analog input voltage to be represented as a digital signal at an analog input terminal;
- supplying a plurality of intermediate voltage levels between said first and second reference voltage levels;
- selecting and applying one of said plurality of intermediate voltage levels to said first input terminal to compensate said integrating circuit for said voltage offset component of said integrating output signal;
- applying said first reference voltage level to said second input terminal of said integrating circuit for a first time period;
- applying said input voltage to said second input terminal of said integrating circuit for a second time period equal to said first time period;
- applying said second reference voltage level to said second input terminal of said integrating circuit for a time period terminated when said integrating output signal is equal to a predetermined voltage level;
- determining a third time period equal in duration to the period that said second reference voltage level was applied to said second input terminal of said integrating circuits;
- and generating a digital signal proportional to said second reference voltage level, said proportion comprising a ratio of said third time period of said first time period, said digital signal comprising said digital representation of said analog input signal.
An integrating analog to digital converter having signal offset error compensation comprising:
- a first reference voltage terminal providing a first reference voltage level;
- a second reference voltage terminal providing a second reference voltage level different from said first reference voltage level;
- an analog input terminal providing an analog input signal to be converted to a digital signal;
- an intermediate voltage generating means for generating a plurality of intermediate voltage levels between said first and second reference voltage levels;
- integrating means having a first input terminal connected to said intermediate voltage generating means and a second input terminal, said integrating means for integrating the voltage level difference between an intermediate voltage level supplied to said first input terminal and a voltage inputted to the second input terminal to produce an integrating output signal including a voltage offset component;
- switch means for selectively coupling one of said first reference voltage level, said second reference voltage level, and said analog input signal with said second input terminal of said integrating means;
- and
- control means for controlling said analog to digital converter to operate in an offset correction mode for compensating for said offset component of said integrating output signal and a converting mode for converting said analog input signal to a digital signal, said control means comprising:
- an offset compensation means for selecting and coupling one of said plurality of intermediate voltage levels to said first input terminal to compensate for said voltage offset component of said integrating output signal;
- and conversion means comprising:
- means for controlling said switch means to supply to said second input terminal (1) said first reference voltage level for a first time period, (2) said analog input signal for a second time period equal in duration to said first time period, and (3) said second reference voltage level for a third time period continuing until said integrating output signal is equal to a predetermined voltage level;
- means for determining the duration of said third time period corresponding to the amount of time said second reference voltage level has been supplied to said second input terminal;
- and
- means for generating a digital signal proportional to said second reference voltage level, said proportion comprising a ratio of said third time period to said first time period, said digital signal comprising a digital representation of said analog input signal.
An integrating analog to digital converter according to claim 14 further including means for continually supplying said selected intermediate voltage level to said first input terminal during the conversion of said analog input signal to said digital representation.
Dependencies are inferred from the claim text.