Pivoting SAR ADC for Autonomous Radiation-Hard Readout

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Solution Overview

Problem

Current readout integrated circuits (ROICs) rely on external support circuitry and are not radiation hard, making them unsuitable for harsh space environments, and require dedicated reference voltages and complex ADC architectures, limiting their autonomy and robustness.

Innovation Solution

A Pivoting Successive Approximation Register (PSAR) analog-digital converter (ADC) that operates with a single power supply voltage, generates its own clock, and is radiation hard by design, allowing it to digitize rail-to-rail input signals without external support, using a segmented DAC and latched comparator with bifurcated convergence phases for enhanced accuracy and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional ADC architectures are used with dedicated reference voltages, then measurement accuracy is improved, but device complexity and reliance on external support circuitry increases

Engineering Contradiction:

Improvemeasurement accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the reference voltage generation function within the ADC architecture itself, eliminating the need for external reference voltage sources. The ADC uses its own power supply voltage as reference, merging the reference function with the main power supply function, thereby reducing external support circuitry while maintaining measurement accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The power supply voltage serves dual purposes: it powers the ADC circuitry and simultaneously serves as the reference voltage for conversions. This multi-functionality eliminates dedicated reference voltage circuitry, reducing device complexity while preserving measurement precision.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If radiation shielding and external support circuitry are added to protect ROICs, then reliability in radiation environments is improved, but device complexity and autonomy deteriorates

Engineering Contradiction:

Improveradiation hardnessVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The ADC is designed to be self-sufficient by generating its own clock signals and using its power supply voltage as reference, eliminating dependence on external support circuitry. This autonomy reduces the need for additional protective and support components, maintaining reliability while reducing complexity.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The ADC architecture is segmented into independent functional blocks (sampling circuit, holding circuit, conversion circuit) that can operate autonomously. This modular segmentation allows each block to be optimized for radiation hardness without requiring complex external support systems.

Inventive Principle:

Principle #1Segmentation

3Productivity

If fast conversion speed is achieved through complex ADC architectures, then productivity is improved, but device complexity and power consumption increase

Engineering Contradiction:

Improveconversion speedVSAvoiddevice complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The input signal is sampled and held at a stable voltage level before conversion begins. This preliminary sampling and holding action prepares the signal in advance, enabling faster conversion without requiring complex high-speed circuitry, thus achieving high productivity with reduced device complexity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The ADC architecture dynamically switches between sampling mode and conversion mode, optimizing performance for each phase. The circuit transitions smoothly between states, enabling fast conversion speeds without requiring permanently complex high-speed circuitry that would increase power consumption and complexity.

Inventive Principle:

Principle #15Dynamics

4Speed

If specialized internal components such as boosted or bootstrapped switches are used, then switching performance is improved, but reliability and simplicity deteriorate due to voltages exceeding power supply

Engineering Contradiction:

Improveswitching performanceVSAvoidreliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The switching circuitry operates within the standard power supply voltage range by changing the operating parameters of the switches. Instead of using boosted or bootstrapped switches that generate voltages exceeding the power supply, the design adjusts switch timing and control signals to achieve adequate switching performance within safe voltage limits, improving reliability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11522552B1Pivoting successive approximation register ADC for a radiation hard autonomous digital readout

Publication Date: 2022.12.06 UNITED STATES OF AMERICA AS REPRESENTED BY THE ADMINISTRATOR NAT AERONAUTICS & SPACE ADMINISTRATION

AI summary

An analog digital converter that does not require a dedicated reference voltage, can digitize a rail-rail input signal and provide house-keeping functions to a ROIC or other IC. The RHADR system may operate without support from a main electronics board, which would only have to supply a power supply voltage to, and read the outputs from, the chip. This is achieved with (1) a Pivoting Successive Approximation Register ADC (PSAR ADC) and (2) radiation hard by design (RHBD) techniques.