Reference Voltage Buffer Using Current-Sensed Tunable Feedback
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Solution Overview
Problem
Conventional reference voltage buffers in pipelined ADCs require high-speed operational trans-conductance amplifiers to maintain constant reference voltages, which leads to high power consumption.
Innovation Solution
A reference voltage buffer circuit using an operational trans-conductance amplifier with a shunt capacitor and a tunable resistor, where the resistance is adjusted in a closed-loop manner to ensure the second current output equals the first current, allowing for fast settling without excessive power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed operational trans-conductance amplifiers are used to maintain constant reference voltages, then the settling speed is improved, but the power consumption increases
Solution Approach 1:
The patent implements a two-phase operating mode for the operational trans-conductance amplifier: a first mode during the transfer phase with higher trans-conductance for fast settling, and a second mode during the sampling phase with lower trans-conductance for reduced power consumption. The amplifier dynamically switches between these modes based on the operational phase, resolving the contradiction between speed and power consumption.
Solution Approach 2:
The patent employs periodic switching between different operational modes synchronized with the pipelined ADC phases. The operational trans-conductance amplifier alternates between high-speed mode and low-power mode in periodic cycles corresponding to the transfer phase and sampling phase respectively, achieving both fast settling when needed and low power consumption during idle periods.
2Productivity
If larger trans-conductance is used in the operational trans-conductance amplifier, then the settling speed is improved, but the power consumption increases
Solution Approach 1:
The patent makes the trans-conductance parameter dynamic by implementing two distinct trans-conductance values: a first (higher) trans-conductance during the transfer phase for fast settling, and a second (lower) trans-conductance during the sampling phase for reduced power consumption. This dynamic parameter adjustment resolves the contradiction between productivity and power.
Data Source
AI summary
A fast settling reference voltage buffer and method are disclosed. In one of embodiments, An apparatus comprising: an OTA (operational trans-conductance amplifier) with a positive input terminal coupled to a reference voltage, a negative input terminal coupled to a feedback node, and an output terminal coupled to a circuit node shunt to ground by a shunt capacitor via a current sensor; a tunable resistor, controlled by a control signal, coupling the circuit node to the feedback node; a load circuit coupled to the feedback node via a switch controlled by a logical signal; and a control circuit for receiving an output of the current sensor and outputting the control signal, wherein the control signal is adapted in accordance with the output of the current sensor.