Isolation Inductors in Time-Interleaved ADCs for Kickback Settling
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Solution Overview
Problem
High-speed, high-resolution analog-to-digital converters (ADCs) face performance degradation due to voltage kickback from track-and-hold circuits, which requires additional power consumption and increased buffer area to settle, especially in time-interleaved configurations.
Innovation Solution
Incorporating isolation inductors electrically coupled to the output of the input buffer and track-and-hold circuits, phase-offsetting drive signals to ensure only one sampling switch transitions per clock cycle, thereby isolating voltage kickback and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional power is supplied to the input buffer to increase bandwidth and reduce output impedance, then voltage kickback settling improves, but power consumption and buffer area increase
Solution Approach 1:
An isolation inductor is introduced as an intermediary component between the input buffer and the track-and-hold circuits. This inductor acts as a mediator that blocks the propagation of voltage kickback from the switching capacitors back to the buffer output, thereby improving voltage kickback settling without requiring additional buffer power consumption or increasing buffer area.
2Speed
If multiple track-and-hold circuits are driven in sequence by a single buffer, then ADC conversion speed increases, but voltage kickback effects are exacerbated
Solution Approach 1:
The circuit is segmented by introducing separate isolation inductors for each track-and-hold circuit or group of circuits. This segmentation isolates the voltage kickback effects to individual branches, preventing them from affecting other parallel track-and-hold circuits. The buffer can continue to drive multiple T/H circuits in sequence at high speed, while each isolated branch handles its own kickback independently.
3Reliability
If buffer output impedance is reduced to absorb voltage kickback, then signal settling improves, but buffer area and power dissipation increase
Solution Approach 1:
The isolation inductor serves as an intermediary that provides the necessary impedance isolation without requiring the buffer itself to have reduced output impedance. The inductor's reactance at the switching frequency provides the isolation function, allowing the buffer to maintain its original design parameters (area, power consumption) while still achieving good signal settling through the isolated T/H circuits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces voltage kickback, minimizing additional power needed to settle signal-dependent fractions and enhancing tracking bandwidth with minimal increase in semiconductor die area.
Implementation Method 1
an isolation inductor electrically coupled to the output of the input buffer and at least one of the track-and-hold circuits
Data Source
AI summary
A time-interleaved circuit includes an input buffer, a plurality of track-and-hold circuits, and a plurality of isolation inductors. The input buffer is configured to receive an input signal having an input voltage and to output an output signal having an output voltage. The track-and-hold circuits are electrically coupled in parallel with each other. Each track-and-hold circuit is electrically coupled in series with the input buffer. Each isolation inductor is electrically coupled to the output of the input buffer and at least one of the track-and-hold circuits.