On-Chip Resistor Divider Compensation for 2Vrms Audio Noise
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Solution Overview
Problem
Modern integrated circuits with low-voltage processes cannot handle full 2Vrms audio signals, requiring signal reduction, which introduces noise due to mismatch between external and internal ground paths in resistor dividers.
Innovation Solution
A compensation system that adjusts the internal ground sense path using a controllable resistor trim within a compensation circuit to match feedback ratios, reducing noise by skewing the internal ground sense path and compensating for polysilicon resistance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an external resistor divider is used to reduce the 2Vrms input signal to a level suitable for low-voltage integrated circuits, then the input signal level is reduced to an acceptable range, but noise is introduced due to mismatch between external and internal ground paths
Solution Approach 1:
The patent introduces an intermediary compensation circuit that includes a controllable resistor trim element placed in the internal ground sense path. This intermediary component acts as a mediator between the external resistor divider and the internal circuitry, allowing adjustment of the ground sense path resistance to match the external path resistance, thereby eliminating ground mismatch noise while preserving the signal level reduction function
Solution Approach 2:
The patent applies parameter changes by making the internal ground sense path resistance adjustable through a controllable resistor trim element. By varying this resistance parameter to match the external resistor divider ratio, the system optimizes ground path matching and minimizes noise introduction, resolving the contradiction between signal level reduction and noise generation
2Object-affected harmful factors
If the internal ground sense path is adjusted to match external ground, then noise from ground mismatch is reduced, but additional circuit complexity is introduced
Solution Approach 1:
The patent applies local quality by introducing the compensation function only in the specific location where ground mismatch occurs - the internal ground sense path. Rather than redesigning the entire input circuitry, a localized controllable resistor trim element is inserted only in the ground sense path to provide the necessary resistance matching, minimizing overall circuit complexity while effectively addressing the noise problem
3Ease of manufacture
If polysilicon resistors are used in the integrated circuit, then manufacturing is simplified, but resistance variations introduce noise
Solution Approach 1:
The patent implements feedback through a controllable resistor trim element that allows post-fabrication adjustment of the internal ground sense path resistance. This feedback mechanism compensates for polysilicon resistor variations by enabling tuning of the ground path resistance to match external resistors, thereby maintaining manufacturing simplicity while achieving precise resistance matching and reducing noise
Data Source
AI summary
A new compensation system for an audio input reduces noise by matching feedback ratios in the positive and negative paths. A variable resistance network allows for fine control of resistance trimming in one of the signal paths, which allows for compensation between tolerance of resistors that are external to an integrated circuit and those that are internal to the integrated circuit.