Recirculating Time-to-Digital Converter With Ring Oscillator Error Correction
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Solution Overview
Problem
Conventional time-to-digital converters (TDCs) face challenges in achieving high resolution and large dynamic range while minimizing power consumption and IC area, with issues such as trade-offs between resolution and dynamic range, linearity problems due to component mismatch, and high power consumption in ring oscillator-based designs.
Innovation Solution
A recirculating TDC design that includes a ring oscillator module with a phase sampler, counter clock generator, counters, data sampler, and digital error correction module, operating in two modes to switch the ring oscillator on and off based on a preset signal, and using a digital control module with a pseudo-random code generator to randomly address inverters for each conversion cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of inverter stages is increased to extend dynamic range, then dynamic range is improved, but power consumption increases and IC area increases
Solution Approach 1:
The ring oscillator is configured to operate in periodic cycles with active and inactive phases. During the active phase, the oscillator runs and performs time interval measurement. During the inactive phase, the oscillator is turned off to save power. This periodic operation allows the system to achieve large dynamic range without continuous high power consumption that would result from keeping many inverter stages constantly active.
Solution Approach 2:
The patent discards the continuous operation mode and recovers energy by turning off the ring oscillator during inactive periods. The oscillator is重新启动 when needed for measurement, thereby recovering power that would otherwise be wasted in continuous operation of a large number of inverter stages.
2Measurement precision
If the number of inverter stages is increased to extend dynamic range, then dynamic range is improved, but IC area increases
Solution Approach 1:
By using periodic operation of the ring oscillator, the patent achieves large dynamic range through multiple measurement cycles rather than through a large number of simultaneously active inverter stages. This reduces the required IC area while maintaining the ability to measure large time intervals.
Solution Approach 2:
The patent introduces dynamic control of the ring oscillator through enable signals that activate or deactivate the oscillator based on measurement needs. This dynamic operation allows the system to achieve large dynamic range without requiring a static, large-scale inverter structure that would occupy excessive IC area.
3Measurement precision
If more inverter stages are added to increase dynamic range, then dynamic range is improved, but linearity deteriorates due to mismatch among inverter stages
Solution Approach 1:
The patent incorporates digital error correction modules that use feedback mechanisms to detect and correct non-linearity errors in the time interval measurement. The correction logic analyzes the relationship between start and stop signals and applies compensatory adjustments, thereby maintaining high linearity even when using a variable number of inverter stages for extended dynamic range.
Solution Approach 2:
The patent changes the operational parameters of the ring oscillator dynamically, including the number of active inverter stages, oscillation frequency, and phase sampling points. By adjusting these parameters based on measurement requirements, the system achieves large dynamic range while maintaining linearity through optimal parameter selection rather than relying on a fixed large number of inverter stages.
4Reliability
If the ring oscillator runs continuously to enable measurement, then measurement capability is maintained, but power consumption increases
Solution Approach 1:
The ring oscillator operates periodically rather than continuously. It is activated only when a time interval measurement is required and deactivated during inactive periods. This periodic operation maintains measurement capability when needed while dramatically reducing average power consumption compared to continuous operation.
Solution Approach 2:
The system includes control logic that automatically manages the activation and deactivation of the ring oscillator based on measurement requirements. The oscillator serves itself by entering low-power states when not needed and activating only when measurement functions require it, eliminating the need for continuous power supply.
Data Source
Figure 1a~1b
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AI summary
A time-to-digital converter (TDC) (300) is disclosed, which comprises a ring oscillator module (302) and a digital error correction module (304). The ring oscillator module is configured to receive a sampling signal, an addressing signal, and a preset signal, and includes: a ring oscillator (3022) arranged with a plurality of inverters (3024); a phase sampler (3028) configured to sample phase signals generated by the inverters of the ring oscillator for generating a first output signal, on receipt of the sampling signal; a counter clock generator (3028) configured to generate first and second clock signals, based on receipt of the sampling signal and respective phase signals generated by the first and last inverters of the ring oscillator; first and second counters (3030, 3032) configured to respectively generate first and second counter output signals, based on receipt of the first and second clock signals respectively: and a data sampler (3034) configured to sample the first and second counter output signals to respectively generate second and third output signals. The digital error correction module is arranged to process the first, second and third output signals for generating a digital signal representative of a time difference between receipt of a start signal and receipt of a stop signal by the TDC.