Multi-Input ADC Code Modulation With Shared Track-and-Hold
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Solution Overview
Problem
Designing high-speed analog-to-digital converters (ADCs) that meet performance, power, and area requirements is challenging due to timing and bandwidth mismatches between channels, especially at high speeds, leading to complex and power-hungry track and hold (T/H) circuits.
Innovation Solution
Implementing a single, dedicated T/H circuit for multiple time-interleaved ADCs to eliminate timing and bandwidth mismatches, and using additive and multiplicative dither for calibration to linearize the T/H circuit and ADC non-idealities, reducing power consumption and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple separate T/H circuits are used for time-interleaved ADCs, then each channel can be independently optimized, but timing and bandwidth mismatches occur between channels leading to increased complexity and power consumption
Solution Approach 1:
The patent merges multiple T/H circuits into a single shared T/H circuit that serves multiple time-interleaved ADC channels. This consolidation eliminates the timing and bandwidth mismatches between separate circuits while maintaining high-speed conversion capability through code modulation techniques that multiplex multiple inputs through the single circuit.
Solution Approach 2:
The single T/H circuit is designed to handle multiple input channels universally through code modulation. The circuit performs multiple functions by sequentially processing different input channels with unique code sequences, allowing one circuit to replace what would traditionally require multiple separate circuits.
2Reliability
If multiple separate T/H circuits are used for time-interleaved ADCs, then channel independence is maintained, but power consumption increases due to redundant circuitry
Solution Approach 1:
By combining multiple T/H circuits into one shared circuit, the patent eliminates redundant power-consuming components while maintaining channel independence through code modulation. The single circuit serves all channels, dramatically reducing overall power consumption compared to having separate circuits for each channel.
Solution Approach 2:
The system uses calibration signals and code modulation sequences that enable the single T/H circuit to self-calibrate and maintain accuracy across all channels without requiring separate calibration circuits for each channel, further reducing power consumption.
3Device complexity
If code modulation is used to multiplex multiple inputs, then a single T/H circuit can handle multiple channels, but calibration complexity increases to correct for non-idealities
Solution Approach 1:
The patent applies preliminary calibration using known code sequences and calibration signals before normal operation. This pre-calibration process characterizes the T/H circuit's non-idealities and stores correction factors, simplifying the operation during actual signal conversion and reducing real-time calibration complexity.
Solution Approach 2:
The system implements feedback-based calibration where calibration signals are processed through the T/H circuit and the results are used to generate correction factors. These feedback mechanisms automatically adjust for timing skew, bandwidth mismatches, and other non-idealities, managing calibration complexity through systematic measurement and correction.
Data Source
AI summary
A multi-input analog-to-digital converter (ADC), i.e., a single ADC, can receive multiple analog input signals and generate multiple digital outputs. To combine multiple analog input signals into a single multi-input ADC, the multi-input ADC would typically include multiple track and hold (T/H) circuits and an adder, which can consume a significant amount of power and incur large cost overhead. An improved approach is to combine multiple inputs through a unique T/H circuit in the front-end of the ADC. The multiple analog input signals can be aggregated using code sequences, without requiring a significant amount of external circuits.