Regulated Switch Driving Scheme for Opamp-Sharing ADCs
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Solution Overview
Problem
Switched-capacitor amplifier circuits face challenges in high-speed and high-resolution ADC designs due to the introduction of extra design complexity, series resistance, and charge injection errors from opamp-sharing techniques, which are exacerbated by process, voltage, and temperature variations.
Innovation Solution
A regulated switch driving scheme is implemented, using a regulated power supply voltage to drive input switches in switched-capacitor amplifier circuits, ensuring optimal operation and isolation from power supply and process variations, allowing for effective opamp-sharing while maintaining high speed and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If opamp-sharing technique is used to reduce power consumption and silicon area, then power efficiency is improved, but device complexity increases and settling time deteriorates due to extra series resistance from additional switches
Solution Approach 1:
The patent merges the functions of multiple switches (M3, M4) into a single regulated switch controlled by a unified clock signal. This consolidation maintains the opamp-sharing topology's power efficiency while reducing the number of discrete switching elements, thereby lowering circuit complexity and minimizing series resistance effects.
Solution Approach 2:
The patent introduces a dynamically regulated switch with controlled impedance that adapts its resistance characteristics based on operational requirements. By using a regulated switch instead of fixed-size switches M3 and M4, the circuit achieves optimal settling time while maintaining the power-saving benefits of opamp-sharing.
2Speed
If switch size is increased to reduce series resistance for high speed operation, then settling time is improved, but charge injection error increases which degrades ADC linearity
Solution Approach 1:
The patent changes the key parameter from fixed switch size to dynamically regulated switch impedance. By controlling the switch impedance through regulation rather than relying on large physical dimensions, the circuit achieves fast settling speed without the excessive charge injection that plagues large-switch designs. This parameter transformation resolves the trade-off between speed and linearity.
Solution Approach 2:
The regulated switch acts as an intermediary between the clock signal and the capacitor nodes, mediating the charge transfer process. This intermediary control mechanism allows precise management of charge injection, enabling fast settling while maintaining ADC linearity by preventing the excessive charge injection that would result from using large switches.
3Use of energy by moving object
If switch size is optimized for low power supply voltage, then power efficiency is improved, but performance deteriorates at high supply voltage, low temperature, and fast process conditions
Solution Approach 1:
The patent employs a dynamically regulated switch that adapts its characteristics in real-time based on operating conditions. Unlike fixed-size switches optimized for specific PVT corners, the regulated switch automatically adjusts its impedance and drive strength to maintain optimal performance across all power supply voltages, temperatures, and process variations, thereby achieving both power efficiency and PVT tolerance.
Solution Approach 2:
The regulated switch serves multiple functions simultaneously: it provides low series resistance for fast settling, minimizes charge injection for high linearity, and adapts to various PVT conditions. This multi-functional design replaces the need for separate optimization for each operating condition, making the circuit universally applicable across different power supply voltages, temperatures, and process corners.
4Use of energy by moving object
If additional switches M3 and M4 are added to implement opamp-sharing, then power consumption is reduced, but charge injection errors increase resulting in larger offset and inferior linearity
Solution Approach 1:
The patent merges the charge transfer functions of switches M3 and M4 into a single regulated switch. This consolidation eliminates the cumulative charge injection errors that arise from multiple switching operations, thereby reducing offset and improving linearity while preserving the power-saving benefits of opamp-sharing architecture.
Solution Approach 2:
The regulated switch serves as a controlled intermediary that manages charge transfer to capacitor nodes C1 and C2. By regulating the switching process, it minimizes charge injection errors compared to the unregulated M3 and M4 switches, thereby reducing offset and improving ADC linearity while maintaining power efficiency.
Data Source
AI summary
A switched-capacitor amplifier circuit including first and second pairs of sampling capacitors for sampling a pair of input signals includes a voltage regulator coupled to receive a first reference voltage and generate a first regulated output voltage related to the first reference voltage and independent of a first power supply voltage; a clock signal generator generating first and second clock signals referenced to the first power supply voltage and third and fourth clock signals referenced to the first regulated output voltage; and a first set of switches coupling the bottom plates of the sampling capacitors to the amplifier, the first set of switches being controlled by the third and fourth clock signals. The circuit may further include a second set of switches coupling the top plates of the sampling capacitors to the input signals, the second set of switches being controlled by the first and second clock signals.