Buffered Bandgap Reference Circuit for Burst-Mode Low-Noise ADCs
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Solution Overview
Problem
Conventional reference circuits face challenges in providing high bandwidth while minimizing noise and power consumption, especially during burst mode operations, leading to errors in analog-to-digital converter (ADC) outputs due to loading effects and electrical noise.
Innovation Solution
A load-independent reference circuit incorporating a buffered bandgap reference stage, filtered by an operational transconductance amplifier and capacitor, which isolates the reference stage from loading effects and reduces noise, employing a resistor ladder for initial accuracy adjustments and a buffer to maintain stability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional reference circuits are used to provide reference signals, then the circuit can operate with simple structure, but the bandwidth is limited and noise performance deteriorates under burst mode operations
Solution Approach 1:
The reference circuit is divided into distinct functional stages: a reference voltage generation stage, a filtering stage with operational transconductance amplifier and capacitor, and a buffer stage. This segmentation allows each stage to be optimized independently - the filtering stage reduces noise while the buffer stage provides high bandwidth and isolates loading effects, resolving the contradiction between bandwidth and noise performance.
Solution Approach 2:
An operational transconductance amplifier is introduced as an intermediary element between the reference voltage source and the output buffer. This intermediary actively filters noise from the reference signal while maintaining high bandwidth characteristics, and its presence allows the circuit to achieve both low noise and high bandwidth simultaneously under burst mode operations.
2Measurement precision
If the reference circuit is directly connected to the load circuit, then the structure is simple, but loading effects cause errors in ADC outputs
Solution Approach 1:
A buffer stage is introduced as an intermediary between the reference circuit and the load circuit (ADC). This buffer isolates the reference voltage generation from loading effects while maintaining signal integrity, thereby improving ADC output accuracy without requiring complex compensation circuits.
Solution Approach 2:
The buffer stage is designed to automatically compensate for loading effects through its high output impedance and voltage buffering capability. The circuit self-regulates to maintain accurate reference voltage levels regardless of the load conditions, eliminating the need for external calibration or complex feedback mechanisms.
3Object-affected harmful factors
If filtering components are added to reduce noise, then noise performance improves, but power consumption increases
Solution Approach 1:
The operational transconductance amplifier is configured with optimized parameter values - specifically, the transconductance gain and capacitor values are tuned to achieve maximum noise filtering efficiency at minimum power consumption. This parameter optimization allows the filtering stage to reduce electrical noise to less than 3 microvolts peak-to-peak while maintaining low power operation.
Solution Approach 2:
The filter capacitor is designed to operate with periodic charging and discharging cycles synchronized with the burst mode operation. This periodic action allows the filter to accumulate and release energy efficiently, reducing noise during critical periods while minimizing average power consumption across the operating cycle.
Data Source
AI summary
A reference circuit may include a bandgap reference stage, a filter stage, and a buffer stage. The reference stage may be configured to generate a reference voltage or current. The filter stage may be coupled to the reference stage and may be configured to receive the reference voltage or current, filter noise from the reference voltage or current, receive a buffer output voltage or current, and filter noise from the buffer output voltage or current. The buffer stage may be coupled to the filter stage and may be configured to isolate the reference stage and the filter stage from a loading effect of a load circuit and generate a reference signal based on the reference voltage or current to drive the load circuit.