US 6,570,523 B1Granted

Analog to digital converter using subranging and interpolation

AssigneeIntersil Americas Inc.

InventorsKantilal Bacrania, Hsin-Shu Chen, Eric C. Sung, Bang-Sup Song, J. Mikko Hakkarainen, Brian L. Allen, Mario Sanchez

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Abstract

A multistage ADC that subranges and interpolates, and that amplifies selected subranges to convert an analog signal to a stream of digital values. The ADC samples the analog signal and provides a stream of sample signals. A first stage flash converts each sample signal into a first multiple bit value and subranges a reference ladder according to the first multiple bit value into selected reference signals. Each additional secondary stage amplifies a selected subrange of signals from a prior stage, flash converts the amplified residual signals to provide an additional multiple bit value, interpolates each set of amplified residual signals and subranges the interpolated signals according to the corresponding multiple bit value. A final stage amplifies and flash converts to determine a final multiple bit value. An error corrector combines each set of multiple bit values into a digital value.

Claims40

Dependent claims

An analog to digital converter (ADC), comprising:

a sampler that regularly samples an input analog signal and that provides a stream of sample signals;
a first stage, coupled to the sampler, that flash converts the stream of sample signals into corresponding primary multiple bit values and that subranges a reference ladder for each primary multiple bit value into corresponding sets of reference signals;
at least one secondary stage, each secondary stage coupled in sequential order after the first stage, that amplifies each set of residual signals from a prior stage, that interpolates each set of amplified residual signals using a resistive ladder, that flash converts each set of amplified residual signals into corresponding secondary multiple bit values, and that subranges the resistive ladder into corresponding sets of residual signals for each corresponding secondary multiple bit value;
and
a final stage that amplifies each set of residual signals from a prior stage and that flash converts each set of amplified residual signals of the final stage into corresponding final multiple bit values;
and
an error corrector, coupled to the first and final stages and each secondary stage, that combines each primary multiple bit value with one or more corresponding secondary multiple bit values and a corresponding final multiple bit value to provide a corresponding stream of digital values representative of the input analog signal.

4 more elements

An analog to digital converter, comprising:

a track and hold circuit that samples an analog signal;
a flash ladder;
a first flash converter, coupled to the flash ladder and receiving a sample of the analog signal, that generates a first set of bits;
a reference resistive ladder having a plurality of tapped reference voltages;
first select logic, coupled to the first flash converter and the reference resistive ladder, that selects a portion of the reference resistive ladder corresponding to the first set of bits;
a first set of preamplifiers, coupled to the first select logic and the reference resistive ladder, that amplifies a difference between the analog sample and each of the plurality of tapped voltages of the selected portion of the resistive reference ladder;
a first interpolator resistive ladder that interpolates the outputs of the first set of amplifiers;
a second flash converter, coupled to the first set of amplifiers, that determines a second set of bits indicative of a zero-crossing of outputs of the first set of preamplifiers;
second select logic, coupled to the second flash converter, the first set of preamplifiers and the first interpolator resistive ladder, that selects a plurality of tapped voltages within a portion of the first interpolator resistive ladder corresponding to the second set of bits;
a second set of preamplifiers, coupled to the second select logic and the first interpolator resistive ladder, that amplifies a difference of each of the selected plurality of tapped voltages of the first interpolator resistive ladder;
a third flash converter, coupled to the second set of amplifiers, that determines a third set of bits indicative of a zero-crossing of outputs of the second set of preamplifiers;
and
a combiner that combines the first, second and third sets of bits to provide a digital value representative of the sample.

10 more elements

A method of converting an analog signal to digital values, comprising:

regularly sampling the analog signal to provide a stream of sample signals;
dividing a reference signal into a plurality of intermediate signals and separately into a plurality of reference signals;
flash converting each sample signal with the plurality of intermediate reference signals to determine corresponding first binary values;
selecting a subrange of the plurality of reference signals based on each first binary value;
amplifying a difference between each sample signal and each reference signal of a corresponding selected subrange of reference signals to provide corresponding sets of first amplified residual signals;
flash converting each set of first amplified residual signals to determine corresponding second binary values;
interpolating each set of first amplified residual signals to provide corresponding sets of first interpolated signals;
selecting a subrange of signals of each set of first interpolated signals based on each second binary value;
amplifying the subrange of signals of each set of first interpolated signals to provide corresponding sets of second amplified residual signals;
flash converting each set of second amplified residual signals to determine corresponding third binary values;
and
combining corresponding sets of first, second and third binary values to generate a digital output value.

9 more elements

Dependencies are inferred from the claim text.