Phase Interpolator Non-Linearity Calibration Without External Pins
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Solution Overview
Problem
Existing methods for measuring non-linearity in Phase Interpolator (PI) of wire-line receivers require additional pins and external hardware, leading to increased chip area costs and complexity, while also being prone to accuracy issues due to parasitic capacitances and transmission line mismatches.
Innovation Solution
The proposed solution involves using a pattern generator to create a data sequence that allows for the measurement of non-linearity in the PI by determining the Bit Error Rate (BER) at different PI codes, thereby calculating the Differential Non-Linearity (DNL) and Integral Non-Linearity (INL) without the need for additional pins or external hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional pins and external hardware are used to measure non-linearity in the Phase Interpolator, then measurement capability is improved, but chip area cost and device complexity increase
Solution Approach 1:
The invention extracts the non-linearity measurement function from external hardware and implements it within the receiver using existing internal components. The pattern generator creates test data sequences that exercise the PI, and the error detector measures bit errors to infer non-linearity characteristics without requiring external measurement equipment or additional pins.
Solution Approach 2:
The invention makes existing receiver components multi-functional. The pattern generator, previously used only for normal data transmission testing, is also used for PI non-linearity measurement. The error detector, originally for detecting transmission errors, now also serves to measure PI non-linearity by analyzing bit error patterns under controlled phase interpolation conditions.
2Measurement precision
If additional pins and external hardware are used to measure non-linearity in the Phase Interpolator, then measurement capability is improved, but manufacturing cost increases
Solution Approach 1:
The invention removes the need for external measurement equipment (oscilloscopes, phase meters, etc.) by implementing the measurement function entirely within the receiver using existing components. This eliminates the need for additional pins and external hardware, directly reducing manufacturing costs while maintaining measurement capability.
Solution Approach 2:
The receiver performs self-diagnosis and self-characterization by using its own internal resources to measure its PI non-linearity. The pattern generator generates test signals, the PI processes them, and the error detector analyzes the results, allowing the device to characterize itself without external assistance, thereby reducing manufacturing complexity and cost.
3Speed
If traditional methods with parasitic capacitances and transmission lines are used to retrieve clocks, then clock retrieval is achieved, but measurement accuracy deteriorates
Solution Approach 1:
The invention extracts the measurement process from the physical domain (requiring clock retrieval through parasitic-capacitance-prone transmission lines) and moves it to the logical/domain level. Instead of measuring phase difference between retrieved clocks using external equipment, the system infers PI non-linearity from bit error patterns, eliminating the accuracy-degrading transmission line and parasitic capacitance elements from the measurement path.
Data Source
AI summary
Methods and systems for determining and calibrating non-linearity in a phase interpolator. Embodiments determine a first jitter value that causes the bit error rate (BER) of a data sequence to exceed a predefined target BER, when a recovered clock is aligned with the data sequence at a first PI code. The recovered clock is obtained from a data pattern representing the data sequence. Embodiments determine a second jitter value that causes the BER of the data sequence to exceed the predefined target BER at a second PI code. The first PI code may immediately precede or succeed the second PI code. Embodiments determine a Differential Non-Linearity (DNL) corresponding to the second PI code, based on a phase shift introduced to the recovered clock by the second PI code relative to the first PI code, the first jitter value, and the second jitter value. All DNL values corresponding to all PI codes may be determined in a similar manner. An Integral Non-Linearity (INL) may be determined by integrating the DNL corresponding to all PI codes.