Microprocessor supervised analog-to-digital converter

• US 4,490,713 A
• Filed: 06/08/1982
• Issued: 12/25/1984
• Est. Priority Date: 11/17/1978
• Status: Expired due to Fees

• Current Assignee: Burr-Brown Corporation (Texas Instruments, Inc.)
• Original Assignee: Burr-Brown Corporation (Texas Instruments, Inc.)
• Inventors: Prazak, Paul R., Mrozowski, Andrij
• Primary Examiner(s): Sloyan, T. J.
• Application Number:
  US06/386,428
• Time in Patent Office: 931 Days
• Field of Search: 340/347 M, 340/347 AD, 364/571, 364/573
• US Class Current: 341/163
• CPC Class Codes: H03M 1/10 Calibration or testing
• CPC Class Codes: H03M 1/44 Sequential comparisons in series-connected stages with change in value of analogue signal

Abstract

An analog-to-digital converter which is supervised by a microprocessor and includes means for digitally compensating for initial gain and offset errors and gain and offset drift errors due to temperature variations. An analog input voltage is applied to a first analog-to-digital converter, the output of which is both stored in the microprocessor and applied to a linear digital-to-analog converter. The output of the linear converter is summed with the original analog input voltage and the difference applied to the conversion apparatus as an unknown input signal. This process is continued to achieve a desired resolution. The output of a differential temperature sensor is similarly processed to determine the proper amount of compensation for gain and offset drift. The microprocessor provides both control and computation capabilities.

Claims

1. A microprocessor supervised analog-to-digital converter implemented to perform a recirculating remainder conversion of an analog input signal, comprising:

analog-to-digital conversion means for performing a first conversion of an analog signal into a digital representation;

a digital-to-analog converter having inputs connected to outputs of said conversion means for producing an analog voltage corresponding to said digital representation;

an error amplifier having a first input coupled to the output of said digital-to-analog converter and a second input coupled to said analog input signal to produce a remainder signal corresponding to the difference therebetween at the output of said error amplifier;

means for substituting said remainder signal for said analog signal to produce a second conversion by said conversion means resulting in the production of a second digital representation and a second remainder signal;

microprocessor means coupled to the outputs of said conversion means for receiving said digital representations simultaneously with the applicaton of said digital representations to said digital-to-analog converter for storing said digital representations and for computing therefrom a digital output corresponding to said analog input signal, said microprocessor means coupled to said substituting means and having means for controlling the number of conversions each of which produces a remainder signal and consequent digital representations thereof, said substituting means comprising;

first and second sample-and-hold circuits controlled by said microprocessor means and having inputs coupled to an output of said error amplifier for alternately receiving and storing successive remainder signals;

first switching means controlled by said microprocessor means for selectively coupling said analog input signal, said first sample-and-hold circuit and said second sample-and-hold circuit to said conversion means; and

second switching means for selectively coupling said analog input signal, said first sample-and-hold circuit and said second sample-and-hold circuit to said error amplifier;

means for producing a voltage indicative of termperature;

means coupled to said means for producing a voltage indicative of temperature and said conversion means for substituting said voltage for said analog input signal, said microprocessor means generating a digital representation of said voltage to determine the amount of drift compensation to be applied to said digital output; and

first storage means coupled to said microprocessor means for storing, in digital form, amounts of drift compensation for various amounts of temperature change, said storage means containing the amount of gain and offset drift which occurs as a function of temperature change.