On-Chip ADC Calibration Signals Using a Ring Oscillator
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Solution Overview
Problem
Time-interleaved analog-to-digital converters (ADCs) face challenges in efficiently generating calibration signals that ensure fast error detection and convergence during calibration, particularly due to intrinsic interleaving errors like DC offset, gain, and skew errors.
Innovation Solution
A system utilizing a ring oscillator to generate calibration signals at various frequencies and amplitudes, allowing for on-chip ADC calibration without reliance on external signals or infrastructure, thereby enabling efficient calibration of ADC errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external calibration signals are used for ADC calibration, then calibration accuracy can be achieved, but chip bring-up time increases and external infrastructure is required
Solution Approach 1:
The patent implements self-service by integrating an on-chip signal generator that produces calibration signals independently without external infrastructure. The signal generator creates test signals directly on the chip to calibrate the ADC, eliminating dependence on external equipment and reducing bring-up time while maintaining calibration accuracy.
2Loss of time
If on-chip signal generation is implemented, then chip bring-up time is reduced and independence from external infrastructure is achieved, but signal generation complexity increases
Solution Approach 1:
The signal generator is designed with multi-functionality to produce various types of test signals (e.g., sine waves, square waves, different frequencies) using a unified circuit architecture. This universal approach reduces overall system complexity compared to having separate dedicated circuits for each signal type, while still providing comprehensive calibration capabilities.
3Productivity
If multiple unit ADCs are time-interleaved to achieve high sampling frequency, then productivity increases, but intrinsic interleaving errors such as DC offset, gain, and skew errors occur
Solution Approach 1:
The calibration system employs feedback mechanisms where the generated test signals are fed through the time-interleaved ADC and the output is analyzed to detect interleaving errors. Based on this feedback, calibration parameters are adjusted to compensate for DC offset, gain mismatches, and skew errors, thereby maintaining high sampling frequency while improving measurement precision.
Data Source
AI summary
A device may include an oscillator and a driver. The oscillator may be coupled to circuitry providing calibration of the oscillator. The oscillator may receive from the circuitry a first signal that causes the oscillator to generate a second signal having a first frequency to be used for calibration of an analog-to-digital converter (ADC). The driver may be coupled to the oscillator and the ADC. The driver may receive the second signal from the oscillator. The driver may receive a third signal indicating an amplitude to apply to the second signal. The driver may provide, to the ADC based at least on the second signal and the third signal, an output signal having the first frequency and the amplitude.