Gearbox Retimer Architecture for Low-Latency ADC-DSP Clock Alignment
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Solution Overview
Problem
Traditional ADC retimer and DSP interface structures suffer from suboptimal power consumption and clock-data-recovery (CDR) performance due to mismatched optimal clock speeds between the DSP and unit-ADCs in time-interleaved SAR ADCs, leading to inefficient power usage and degraded performance.
Innovation Solution
A gearbox retiming architecture is introduced to synchronize the ADC and DSP clock rates by generating multiple clock signals with different frequencies, allowing unit-ADCs and DSP to operate at their optimal frequencies, using a multiplexer to select and align data, and a retimer to combine and realign outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the DSP operates at the same clock as the sampling clock of the unit-ADC, then the system structure is simple, but power consumption increases and CDR performance degrades
Solution Approach 1:
The patent introduces a gearbox retimer that segments the clock synchronization function into distinct stages: a first retimer aligns ADC data to an intermediate clock rate, and a second retimer aligns to the final DSP clock rate. This segmentation allows each retimer stage to operate at optimized clock speeds rather than forcing a single high-speed clock throughout the system, thereby reducing overall power consumption while maintaining functional simplicity.
Solution Approach 2:
The patent introduces an intermediate clock rate as a mediator between the ADC sampling clock and the DSP operating clock. The gearbox retimer uses this intermediate rate to bridge the frequency mismatch, allowing both ADC and DSP to operate at their optimal frequencies without requiring them to run at the same high speed, thus reducing power consumption while maintaining system simplicity.
2Device complexity
If the DSP operates at the same clock as the sampling clock of the unit-ADC, then the system structure is simple, but CDR performance degrades
Solution Approach 1:
The patent segments the clock alignment process into two distinct retimer stages operating at different clock rates. This segmentation allows the first retimer to handle the high-frequency ADC data alignment separately from the second retimer that interfaces with the DSP, thereby optimizing CDR performance at each stage rather than compromising it in a single high-speed interface.
Solution Approach 2:
The intermediate clock rate acts as a mediator that enables optimal CDR performance by providing a transition frequency between the ADC sampling rate and DSP operating rate. This intermediate stage allows the clock-data-recovery circuitry to lock onto a frequency that is optimized for reliable data recovery, rather than being forced to operate at the ADC's higher sampling frequency.
3Device complexity
If a traditional retimer structure is used, then the implementation is simple, but data latency is high
Solution Approach 1:
The patent implements a dynamic multi-rate retimer structure where the first and second retimers operate at different clock rates optimized for their respective functions. This dynamic approach allows the system to process and forward data more efficiently through the pipeline, reducing the time data spends in the retimer compared to a static single-rate structure, thereby reducing overall data latency.
Data Source
AI summary
A low latency gearbox retimer architecture is provided. An apparatus includes a first clock generator configured to generate a first clock signal having a first frequency, and a second clock signal having a second frequency. A control logic is configured to generate the control signal, based, at least in part, on the second clock signal, and two or more analog to digital converter (ADC) slices. Each respective ADC slice includes a multiplexer having a first number of inputs and a second number of outputs, wherein the multiplexer is configured to select a set of the second number of inputs to be output, wherein the set of the second number of inputs selected is based, at least in part, on a control signal. The apparatus includes one or more unit-ADCs, wherein the respective outputs of the one or more unit-ADCs are coupled to the multiplexer as an input.