A/D converter calibration

• US 6,486,807 B2
• Filed: 04/25/2001
• Issued: 11/26/2002
• Est. Priority Date: 04/25/2000
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Jonsson, Bengt Erik
• Primary Examiner(s): YOUNG, BRIAN K
• Application Number:
  US09/842,390
• Publication Number:
  US 20020014982A1
• Time in Patent Office: 580 Days
• Field of Search: 341/120, 341/118, 341/119, 341/135, 341/121
• US Class Current: 341/120
• CPC Class Codes: H03M 1/1057 by trimming, i.e. by individually adjusting at least part of the quantisation value generators or stages to their nominal values
• CPC Class Codes: H03M 1/167 all stages comprising simultaneous converters H03M1/165 takes precedence

Abstract

A pipeline stage in a multi-bit/stage pipeline A/D converter is calibrated by switching a set of D/A converter unit-segments in the stage to predetermined states to produce a first digital signal. A second digital signal is produced by switching a predetermined unit-segment in the set to its complementary state and keeping the states of the other unit-segments in the set unchanged. The unit-segment is then associated with a calibration coefficient representing the deviation of the difference between the first and second digital signals from an expected difference between the first and second digital signals. This process is repeated for each unit-segment that is to be calibrated.

Claims

1. A method of calibrating a pipeline stage in a multi-bit/stage pipeline A/D converter, comprising the steps of:

switching a set of D/A converter unit-segments in the stage to predetermined states for producing a first digital signal from the A/D converter;

switching a predetermined unit-segment in the set to its complementary state, keeping the states of the other unit-segments in the set unchanged, for producing a second digital signal from the A/D converter;

associating the predetermined unit-segment with a calibration coefficient representing the deviation of the difference between the first and second digital signals from an expected difference between the first and second digital signals; and

repeating the previous steps for each unit-segment that is to be calibrated.

2. The method of claim 1, further comprising the step of dividing the other unit-segments into two groups, namely a first group in which all unit-segments are in a common switch state, and a second group in which all unit-segments are in a switch state complementary to the common state.

3. The method of claim 2, wherein the first and second group include the same number of unit-elements.

4. The method of claim 1, further comprising the step of calibrating a pipeline stage by individually calibrating its unit-segments with their associated calibration coefficients.

5. The method of claim 4, further comprising the step of forming a pipeline stage correction on a sample by sample basis by accumulating the calibration coefficients with signs that depend on the current switch states of the associated unit-segments.

6. The method of claim 1, further comprising the step of averaging each calibration coefficient over several samples.

7. The method of claim 1, further comprising the step of combining calibration with dynamic element matching.

8. An apparatus for calibrating a pipeline stage in a multi-bit/stage pipeline A/D converter, comprising:

means for switching a set of D/A converter unit-segments in the stage to predetermined states for producing a first digital signal from the A/D converter;

means for switching a predetermined unit-segment in the set to its complementary state, keeping the states of the other unit-segments in the set unchanged, for producing a second digital signal from the A/D converter;

means for associating the predetermined unit-sternest with a calibration coefficient representing the deviation of the difference between the first and second digital signals from an expected difference between the first and second digital signals; and

means for repeating the previous steps for each unit-segment that is to be calibrated.

9. The apparatus of claim 8, further comprising means for dividing the other unit-segments into two groups, namely a first group in which all unit-segments are in a common switch state, and a second group in which all unit-segments are in a switch state complementary to the common state.

10. The apparatus of claim 9, further comprising means for including the same number of unit-elements in the first and second group.

11. The apparatus of claim 8, further comprising means for calibrating a pipeline stage by individually calibrating its unit-segments with their associated calibration coefficients.

12. The apparatus of claim 11, further comprising means for forming a pipeline stage correction on a sample by sample basis by accumulating the calibration coefficients with signs that depend on the current switch states of the associated unit-segments.

13. The apparatus of claim 8, further comprising means for averaging each calibration coefficient over several samples.

14. The apparatus of claim 8, further comprising means for combining calibration with dynamic element matching.