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WO-2026096187-A1 - NON-LINEARITY CORRECTION OF THERMOMETRIC DAC CODING ERRORS WITH CONFIGURABLE PERMUTATION MULTIPLEXERS

WO2026096187A1WO 2026096187 A1WO2026096187 A1WO 2026096187A1WO-2026096187-A1

Abstract

A Digital-to-Analog Converter (DAC - 100), for converting an input thermometric digital signal to an analog output signal, includes at least two configurable permutation multiplexers (CPMUXes - 104), a bank of unit-DACs (106), and a summer circuit (108). Each CPMUX is configured to map a respective partial subset of bits of the input thermometric digital signal into a respective partial subset of bits of a permuted thermometric digital signal, according to a CPMUX configuration. Each unit-DAC is configured to convert a respective bit of the permuted thermometric digital signal into an analog signal. The summer circuit is configured to generate the analog output signal according to a sum of the analog signals produced by the unit-DACs.

Inventors

  • MILLER, Avi
  • ADIV, Or

Assignees

  • Retym, Inc.

Dates

Publication Date
20260507
Application Date
20251012
Priority Date
20241029

Claims (17)

  1. 1. A Digital -to- Analog Converter (DAC) to convert an input thermometric digital signal to an analog output signal, the DAC comprising: at least two configurable permutation multiplexers (CPMUXes), each CPMUX configured to map a respective partial subset of bits of the input thermometric digital signal into a respective partial subset of bits of a permuted thermometric digital signal, according to a CPMUX configuration; a bank of unit-DACs, each unit-DAC configured to convert a respective bit of the permuted thermometric digital signal into an analog signal; and a summer circuit, configured to generate the analog output signal according to a sum of the analog signals produced by the unit-DACs.
  2. 2. The DAC according to claim 1, further comprising a binary to thermometric-code conversion circuit, configured to convert a digital input signal to the input thermometric digital signal.
  3. 3. The DAC according to claim 1, wherein at least one of the CPMUXes comprises a configurable 2-by-2 multiplexer.
  4. 4. The DAC according to any of claims 1-3, wherein the CPMUX configuration is set to improve a conversion accuracy measure of the DAC.
  5. 5. The DAC according to claim 4, wherein the accuracy measure comprises a linearity measure of the analog output signal.
  6. 6. The DAC according to any of claims 1-3, wherein the CPMUX configuration of at least one of the CPMUXes is stored in a Non-Volatile Memory (NVM).
  7. 7. A method for converting an input thermometric digital signal to an analog output signal, the method comprising: using each of at least two configurable permutation multiplexers (CPMUXes), mapping a respective partial subset of bits of the input thermometric digital signal into a respective partial subset of bits of a permuted thermometric digital signal, according to a CPMUX configuration; using each unit-Digital-to-Analog-Converter (unit-DAC) in a bank of unit-DACs, converting a respective bit of the permuted thermometric digital signal into an analog signal; and generating the analog output signal according to a sum of the analog signals produced by the unit-DACs.
  8. 8. The method according to claim 7, further comprising converting a digital input signal to the input thermometric digital signal.
  9. 9. The method according to claim 7, wherein at least one of the CPMUXes comprises a configurable 2-by-2 multiplexer.
  10. 10. The method according to any of claims 7-9, and comprising setting the CPMUX configuration to improve a conversion accuracy measure of the DAC.
  11. 11. The method according to claim 10, wherein the accuracy measure comprises a linearity measure of the analog output signal.
  12. 12. The method according to any of claims 7-9, and comprising storing the CPMUX configuration of at least one of the CPMUXes in a Non-Volatile Memory (NVM).
  13. 13. A method for calibrating a Digital -to- Analog Converter (DAC), the method comprising: estimating a conversion accuracy measure of a thermometric DAC that converts an input thermometric digital signal to an analog output signal, wherein the thermometric DAC comprises (i) at least two configurable permutation multiplexers (CPMUXes), each CPMUX configured to map a respective partial subset of bits of the input thermometric digital signal into a respective partial subset of bits of a permuted thermometric digital signal, according to a CPMUX configuration, (ii) a bank of unit-DACs, each unit-DAC configured to convert a respective bit of the permuted thermometric digital signal into an analog signal, and (iii) a summer circuit, configured to generate the analog output signal according to a sum of the analog signals produced by the unit-DACs; and adjusting the CPMUX configuration to improve the conversion accuracy measure.
  14. 14. The method according to claim 13, wherein estimating the conversion accuracy measure comprises: measuring respective strengths of the unit-DACs while the CPMUXes are in a pass- through mode; and calculating the conversion accuracy measure for a given CPMUX configuration based on the strengths of the unit-DACs.
  15. 15. The method according to claim 13 or 14, wherein adjusting the CPMUX configuration comprises improving a linearity measure of the analog output signal.
  16. 16. The method according to claim 15, wherein the linearity measure comprises an integral non-linearity (INL) of the DAC.
  17. 17. The method according to claim 15, wherein the linearity measure comprises a differential non-linearity (DNL) of the DAC.

Description

NON-LINEARITY CORRECTION OF THERMOMETRIC DAC CODING ERRORS WITH CONFIGURABLE PERMUTATION MULTIPLEXERS CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application 63/713,079, filed October 29, 2024, whose disclosure is incorporated herein by reference. FIELD OF THE INVENTION The present disclosure relates to digital-to-analog converters (DACs), and more particularly to non-linearity correction techniques for thermometric DACs. BACKGROUND OF THE INVENTION Digital-to-analog converters (DACs) are fundamental components in electronic systems that convert digital signals into corresponding analog outputs. These devices serve as the interface between digital processing systems and analog circuits, enabling applications ranging from audio equipment to communication systems and instrumentation. Thermometric coding represents one approach to DAC implementation that offers advantages in linearity performance compared to traditional binary-weighted architectures. In thermometric coding schemes, each bit in the digital code carries equal weight, and the conversion process typically involves activating a number of identical digital-to-analog conversion elements proportional to the input digital value. This coding method can provide improved monotonicity and reduced differential non-linearity compared to binary-weighted approaches. Despite the theoretical advantages of thermometric coding, practical implementations face challenges related to component matching and manufacturing variations. Process variations during fabrication can cause deviations in the actual weights of individual digital-to-analog conversion elements from their intended values. These mismatches can introduce non-linearities in the DAC transfer function, manifesting as differential non-linearity (DNL) and integral nonlinearity (INL) errors that degrade overall conversion accuracy. SUMMARY OF THE INVENTION An embodiment of the present invention that is described herein provides a Digital-to- Analog Converter (DAC) for converting an input thermometric digital signal to an analog output signal. The DAC includes at least two configurable permutation multiplexers (CPMUXes), a bank of unit-DACs, and a summer circuit. Each CPMUX is configured to map a respective partial subset of bits of the input thermometric digital signal into a respective partial subset of bits of a permuted thermometric digital signal, according to a CPMUX configuration. Each unit- DAC is configured to convert a respective bit of the permuted thermometric digital signal into an analog signal. The summer circuit is configured to generate the analog output signal according to a sum of the analog signals produced by the unit-DACs. In some embodiments, the DAC further includes a binary to thermometric-code conversion circuit, configured to convert a digital input signal to the input thermometric digital signal. In example embodiments, at least one of the CPMUXes includes a configurable 2-by-2 multiplexer. In some embodiments, the CPMUX configuration is set to improve a conversion accuracy measure of the DAC. In an example embodiment, the accuracy measure includes a linearity measure of the analog output signal. In a disclosed embodiment, the CPMUX configuration of at least one of the CPMUXes is stored in a Non-Volatile Memory (NVM). There is additionally provided, in accordance with an embodiment that is described herein, a method for converting an input thermometric digital signal to an analog output signal. The method includes, using each of at least two configurable permutation multiplexers (CPMUXes), mapping a respective partial subset of bits of the input thermometric digital signal into a respective partial subset of bits of a permuted thermometric digital signal, according to a CPMUX configuration. Using each unit-Digital-to-Analog-Converter (unit-DAC) in a bank of unit-DACs, a respective bit of the permuted thermometric digital signal is converted into an analog signal. The analog output signal is generated according to a sum of the analog signals produced by the unit-DACs. There is further provided, in accordance with an embodiment that is described herein, a method for calibrating a Digital-to-Analog Converter (DAC). The method includes estimating a conversion accuracy measure of a thermometric DAC that converts an input thermometric digital signal to an analog output signal, wherein the thermometric DAC includes (i) at least two configurable permutation multiplexers (CPMUXes), each CPMUX configured to map a respective partial subset of bits of the input thermometric digital signal into a respective partial subset of bits of a permuted thermometric digital signal, according to a CPMUX configuration, (ii) a bank of unit-DACs, each unit-DAC configured to convert a respective bit of the permuted thermometric digital signal into an analog signal, and (iii) a summer circuit, configured to generate the analog output signal according