Radiation-Tolerant Voltage Reference Circuit Using Flying Capacitor Isolation
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Solution Overview
Problem
Existing voltage reference circuits in switched-capacitor pipeline or SAR ADCs face noise and drift issues due to ground errors and radiation sensitivity, particularly in high-frequency applications where precise voltage regulation is critical.
Innovation Solution
A radiation-hardened reference circuit using a precision reference circuit with a flying capacitor configuration, where a buffer circuit generates a reference voltage isolated from ground errors by non-overlapping clock signals, ensuring the precision loop remains unaffected by ground voltage differences and radiation events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a precision voltage reference circuit is used in switched-capacitor pipeline ADCs, then the reference voltage regulation precision is improved, but the circuit becomes sensitive to ground bounce and radiation-induced noise
Solution Approach 1:
The reference circuit is divided into two separate domains: a first domain containing the precision reference loop operating at a first ground potential, and a second domain containing the buffer circuit operating at a second ground potential. This segmentation isolates the precision loop from ground bounce and radiation-induced noise in the second domain, while maintaining reference voltage regulation precision through the flying capacitor coupling mechanism.
Solution Approach 2:
A flying capacitor is introduced as an intermediary element to couple the first domain (precision reference loop) and the second domain (buffer circuit). The flying capacitor transfers the regulated reference voltage from the precision loop to the buffer circuit without providing a direct DC path that would allow ground potential differences and noise to affect the precision loop, thus protecting it while maintaining voltage regulation.
2Reliability
If the reference circuit is isolated from ground errors using separate ground potentials, then radiation tolerance is improved, but circuit complexity increases
Solution Approach 1:
The circuit is segmented into two domains with separate ground potentials (first ground potential for precision loop, second ground potential for buffer circuit), allowing the precision reference loop to operate in a clean electrical environment isolated from ground bounce and radiation effects, while the buffer circuit handles the noisy interface to the ADC.
Solution Approach 2:
The flying capacitor serves as an intermediary that couples the two domains with different ground potentials. It transfers the regulated voltage signal from the precision domain to the buffer domain without requiring complex isolation circuitry, achieving radiation tolerance through a relatively simple capacitive coupling mechanism.
3Device complexity
If the precision reference loop is directly coupled to the buffer circuit, then device complexity is reduced, but ground voltage differences cause voltage modulation errors
Solution Approach 1:
The flying capacitor is positioned as an intermediary between the precision reference loop and the buffer circuit. During the first phase, it couples the two circuits to allow the precision loop to regulate the reference voltage. During the second phase, it decouples them to prevent ground voltage differences from causing modulation errors, thus maintaining reference voltage accuracy while using a relatively simple capacitive coupling mechanism.
Solution Approach 2:
The flying capacitor operates in periodic phases: first phase for coupling (allowing precision regulation) and second phase for decoupling (preventing ground-induced modulation errors). This periodic switching enables the circuit to achieve both simplicity and accuracy by alternating between connected and isolated states.
Data Source
AI summary
A radiation-hardened reference circuit includes a precision voltage reference circuit for generating a current-controlling voltage at first and second terminals, a driver circuit for receiving the current-controlling voltage at first and second terminals and for generating an output reference voltage, and a differential sampling circuit having first and second input terminals coupled to the first and second terminals of the voltage reference circuit, and first and second output terminals coupled to the first and second terminals of the driver circuit.