Transition-Enabled VCRO Cells for Low-Current Sigma-Delta Modulators
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Solution Overview
Problem
Voltage-controlled ring oscillators (VCROs) in sigma-delta modulators face challenges due to static current consumption, which degrades signal-to-noise and distortion ratio (SNDR) performance and increases complexity in maintaining linearity.
Innovation Solution
The VCRO cells are designed to be enabled only during switching and disabled otherwise, using transition detectors with comparators and latches to minimize static current consumption without increasing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If VCRO cells are continuously enabled to maintain oscillation, then linearity and SNDR performance are maintained, but static current consumption increases
Solution Approach 1:
The VCRO cells are enabled only during switching transitions rather than continuously operating. Transition detectors generate enable signals periodically when state changes occur, causing the VCRO cells to operate in periodic bursts. This periodic activation maintains the necessary oscillation for accurate quantization while dramatically reducing static current consumption during non-switching periods.
2Loss of energy
If VCRO cells are disabled to reduce current consumption, then power efficiency improves, but linearity and oscillation stability deteriorate
Solution Approach 1:
Transition detectors monitor the state of VCRO cells and provide feedback enable signals based on actual switching events. This feedback mechanism ensures that VCRO cells are activated precisely when needed to maintain oscillation stability during transitions, while remaining disabled during stable states. The feedback loop preserves oscillation stability without requiring continuous operation, thereby improving power efficiency.
3Use of energy by moving object
If transition detectors with comparators and latches are added to control VCRO cells, then current consumption is reduced, but system complexity increases
Solution Approach 1:
The transition detectors are implemented to automatically detect state changes in VCRO cells and generate corresponding enable signals without external control. The comparators and latches within the transition detectors self-regulate the enabling and disabling of VCRO cells based on their own state monitoring, eliminating the need for complex external control circuitry. This self-service approach reduces current consumption while keeping system complexity manageable.
Data Source
AI summary
A voltage-controlled ring oscillator (VCRO) and a VCRO-based sigma delta modulator having capability of enabling and disabling the VCRO cells. A VCRO includes a plurality of inverters coupled in a ring and a transition detector. The transition detector detects a transition of a first inverter and sends a control signal to enable a second inverter if the transition of the first inverter is detected. The transition detector may include a comparator configured to compare an input and an output of an inverter(s) to detect the transition of the first inverter and a latch configured to hold the control signal until it is reset.