Multi-A/D Converter RTZ Signaling for Capacitive Coupling Noise
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Solution Overview
Problem
In A/D conversion integrated circuits, capacitive coupling between digital and analog signal lines leads to noise propagation, making it challenging to separate high-impedance regions effectively, especially in circuits with multiple A/D converters.
Innovation Solution
The integration of an RTZ waveform generator and a switched-capacitor amplifier circuit, along with a signal processing circuit that uses capacitors and an arithmetic amplifier, generates and processes signals with controlled transitions to cancel out noise through parasitic capacitive coupling, ensuring low residual noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If digital and analog conductor lines are arranged close together to increase integration density, then productivity and area utilization are improved, but capacitive coupling noise increases and signal integrity deteriorates
Solution Approach 1:
The patent utilizes the parasitic capacitance that naturally exists between adjacent conductor lines instead of treating it purely as a harmful element. By designing the digital signal waveform to have an even number of transitions (RTZ waveform), the noise generated through the parasitic capacitance is made to cancel itself out, converting the previously harmful capacitive coupling into a benign or even beneficial effect that enables high-density integration without significant noise penalties.
Solution Approach 2:
The patent changes the temporal parameter of the digital signal by using an RTZ (Return-to-Zero) waveform with an even number of transitions instead of conventional waveforms. This parameter change ensures that noise impulses generated through parasitic capacitance during voltage transitions cancel each other out, thereby reducing net noise coupling to adjacent analog lines while maintaining high integration density.
2Object-affected harmful factors
If physical separation distance between digital and analog conductor lines is increased to reduce capacitive coupling, then noise coupling is reduced, but area consumption increases and integration density decreases
Solution Approach 1:
Rather than increasing physical separation distance to reduce noise, the patent accepts the presence of parasitic capacitance and instead modifies the digital signal waveform characteristics. By using RTZ waveforms with an even number of transitions, the noise generated through the unavoidable parasitic capacitance cancels itself out, achieving noise reduction without requiring increased physical spacing, thereby maintaining high integration density.
Solution Approach 2:
The patent applies noise cancellation through waveform design rather than relying on physical separation. By ensuring the digital signal has an even number of transitions, the noise cancellation effect is achieved through the signal's temporal characteristics rather than spatial separation, allowing closer placement of digital and analog lines without excessive area consumption.
3Object-affected harmful factors
If RTZ waveform with even number of transitions is used to cancel noise through parasitic capacitance, then noise propagation is reduced, but circuit complexity increases due to additional waveform generation and control
Solution Approach 1:
The RTZ waveform generator circuit serves multiple functions: it generates the digital signal for A/D conversion, ensures the even number of transitions for noise cancellation, and provides timing control for the switched-capacitor amplifier. By consolidating these functions into a single circuit block, the patent reduces overall system complexity despite the added waveform generation requirements.
Solution Approach 2:
The patent merges the waveform generation function with the existing A/D conversion control logic. The RTZ waveform generator is integrated into the control path of the switched-capacitor amplifier, combining signal generation and conversion control into a unified structure, thereby minimizing the increase in overall circuit complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively inhibits noise propagation by ensuring that noise transitions cancel each other out, maintaining high impedance and reducing residual noise in the A/D conversion process.
Implementation Method 1
there is a possibility of capacitive coupling being formed between another conductor of the analog circuit and a conductor line through which the digital signal propagates
Data Source
AI summary
An A/D conversion integrated circuit including a plurality of A/D converters which can inhibit noises from being propagated by capacitive coupling from a conductor which transmits a digital signal is provided. In an A/D converter 13, an input 15 receives an analog signal to be A/D converted. An output 17 provides at least a part of a digital signal SD having a predetermined number of bits representing the analog signal SA. In response to an analog signal SA, a sub-A/D conversion circuit 19 generates a signal SDP representing one or a plurality of bit values of the digital signal SD and feeds the signal SDP to the output 17. An input 21a of a control circuit 21 is connected to an output 19a of the sub-A/D conversion circuit 19 and provides a control signal SCONT corresponding to the signal SDP. The control signal SCONT has a waveform including a transition from a voltage level L1 to a voltage level L2 and a transition from the voltage level L2 to the voltage level L1.