Current-Mode Sigma-Delta ADC for Low-Noise Resistive Memory Readout
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Solution Overview
Problem
Conventional analog-to-digital converters (ADCs) used in resistive memory systems face challenges with high power consumption, noise generation due to capacitors and switches, and reduced circuit performance, especially when operating in multiple channels, requiring a solution that minimizes noise and maximizes signal processing speed while occupying minimal area.
Innovation Solution
A sigma-delta modulator that directly converts current signals into digital data without using capacitors or switches, employing a delta circuit to generate differential currents, an integration circuit with a transconductance amplifier, and a quantization circuit to produce digital modulation signals, thereby reducing power consumption and noise effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional ADC structures using capacitors and switches are used, then conversion function is achieved, but noise is generated due to jitter, clock feed-through, and charge injection
Solution Approach 1:
The patent removes capacitors and switches from the ADC circuit structure, extracting the noise-generating components while preserving the conversion function through alternative current-based circuitry. This directly addresses the noise problem by eliminating the physical sources of jitter, clock feed-through, and charge injection.
Solution Approach 2:
The patent substitutes the conventional voltage-domain switching mechanism with a current-domain continuous operation system. By replacing mechanical switches and capacitive storage with continuous current flow and transconductance amplification, the system eliminates the discrete switching events that generate noise.
2Use of energy by moving object
If integrator is used for conversion, then conversion function is achieved, but power consumption increases in integration process
Solution Approach 1:
The patent replaces the traditional voltage-domain integrator with a current-domain continuous conversion system. This substitution eliminates the need for capacitive charging/discharging cycles, enabling continuous signal processing without the power consumption penalties of periodic integration while maintaining high conversion speed.
3Reliability
If ADC operates in voltage domain with switch and capacitor structure, then conversion is achieved, but circuit performance is reduced due to noise
Solution Approach 1:
The patent fundamentally substitutes the voltage-domain switching architecture with a current-domain continuous architecture. This replacement moves the operation from discrete voltage levels controlled by switches to continuous current levels, inherently improving reliability by eliminating the noise mechanisms associated with switching and capacitive storage.
4Use of energy by moving object
If ADC operates in time domain, then power consumption is low and operation is high-speed, but resistive memory is vulnerable to variations in PVT
Solution Approach 1:
The patent changes the fundamental operating parameter from voltage (conventional ADC) or time (time-domain ADC) to current. This parameter change enables the system to achieve low power consumption through continuous current operation while improving PVT robustness by using current-mode circuitry that is inherently less sensitive to process, voltage, and temperature variations.
5Adaptability or versatility
If multiple channels operate simultaneously, then system functionality increases, but area occupied by ADC increases
Solution Approach 1:
The patent designs a universal current-domain ADC architecture that can handle multiple channels simultaneously without proportionally increasing area. The continuous current operation mode and absence of per-channel capacitive storage enable channel multiplexing and parallel operation with shared circuit resources, achieving multi-functionality with minimal area overhead.
Data Source
AI summary
Disclosed are a sigma-delta modulator that directly converts a current signal into digital data, an ADC utilizing the sigma-delta modulator, and a neural network computing system utilizing the ADC. The sigma-delta modulator includes: a delta circuit to generate a differential current between an analog current signal output from a resistive memory and a first current included in the analog current signal, the first current having an amount of current determined by a digital modulation signal; an integration circuit to generate an integration current by integrating the differential current; and a quantization circuit to generate the digital modulation signal corresponding to the integration current. The sigma-delta modulator can minimize the generation of noise by using no capacitor that performs a function by a switch, and can increase a signal processing speed for conversion by allowing the signal processing speed to be determined by a signal processing speed of one element.