Hybrid SAR ADC DAC Architecture for Wide Voltage Range Switching
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Solution Overview
Problem
Analog-to-digital converters (ADCs), particularly successive-approximation-register (SAR) ADCs, face issues with switching circuits not functioning properly across certain voltage ranges, leading to unreliable operations.
Innovation Solution
The implementation of a hybrid ADC system that includes a capacitive DAC and multiple resistive DACs, where each resistive DAC is connected to a common voltage through a respective capacitor, sharing a resistor ladder and utilizing NMOS and PMOS transistors in transmission gates to circumvent undesirable voltage ranges and promote reliable operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switching circuits are used in ADC, then the ADC can perform digital signal processing, but the switching circuits may not function properly across certain voltage ranges
Solution Approach 1:
The patent divides the single DAC unit into multiple DAC units (first DAC unit with capacitive DAC and first resistive DACs, second DAC unit with second capacitive DAC and second resistive DACs). Each DAC unit operates in different voltage ranges, segmenting the overall voltage operating range into multiple safe zones. This segmentation allows the ADC to cover a wider voltage range while maintaining reliable switching circuit operation in each segment.
Solution Approach 2:
The patent introduces capacitors as intermediary elements connecting the resistive DACs to the common voltage link. These capacitors isolate the resistive DACs from direct voltage fluctuations, allowing them to operate reliably even when the common voltage link experiences undesirable voltage ranges. The capacitors act as buffers that mediate between the voltage source and the sensitive switching circuits.
2Adaptability or versatility
If multiple resistive DACs are used to expand voltage range, then the ADC operates reliably across wider voltage range, but the device complexity increases
Solution Approach 1:
The patent merges multiple resistive DACs into a unified structure that shares a common voltage link and resistor ladder. Instead of implementing completely separate DAC circuits, the resistive DACs are integrated with shared resources (common voltage link, resistor ladder), reducing the overall device complexity while maintaining the benefit of expanded voltage range operation.
Solution Approach 2:
The common voltage link serves multiple functions: it provides voltage to both the capacitive DACs and resistive DACs, acts as a reference for the comparator, and enables voltage ranging functionality. The resistor ladder is shared among multiple resistive DACs, allowing each DAC to perform different bit conversions while using the same physical components, thereby reducing device complexity.
Data Source
AI summary
Embodiments of an analog-to-digital converter (ADC), resistive digital-to-analog converter (DAC) circuits, and methods of operating an ADC are disclosed. In an embodiment, an analog-to-digital converter includes a DAC unit configured to convert a digital code to a first voltage in response to an input voltage of the ADC, a comparator configured to compare the first voltage with a second voltage to generate a comparison output, and a logic circuit configured to generate the digital code, to control the DAC unit based on the comparison output, and to output the digital code as a digital output of the ADC. The DAC unit includes a capacitive DAC and multiple resistive DACs. Each of the resistive DACs is connected to the first voltage through a respective capacitor.