Receiving Circuit Common Mode Voltage Suppression
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Solution Overview
Problem
Existing signal transmission techniques between semiconductor chips with different power supply voltages suffer from signal transmission errors due to the effect of common mode voltage caused by parasitic coupling capacitors in transformers used for AC coupling.
Innovation Solution
A receiving circuit with a pulse width amplifier circuit and a comparator circuit that holds pulse signals from both ends of a secondary coil with a center tap, suppressing common mode voltage effects without increasing circuit size, by comparing voltages and outputting comparison results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a transformer is used for AC coupling between semiconductor chips with different power supply voltages, then signal transmission between different voltage domains is enabled, but signal transmission errors occur due to common mode voltage effects from parasitic coupling capacitors
Solution Approach 1:
The patent divides the signal reception process into two separate paths: one for receiving the differential signal through the transformer, and another for generating a common mode voltage reference. By segmenting the common mode voltage generation from the differential signal path, the patent eliminates the harmful coupling effect while maintaining the ability to transmit signals between different voltage domains.
Solution Approach 2:
The patent introduces an intermediary circuit that generates the common mode voltage based on the power supply voltages of both the transmitting and receiving sides, rather than directly coupling through the transformer. This intermediary approach allows the system to compensate for voltage differences without introducing parasitic coupling errors.
2Reliability
If circuit structures are added to suppress common mode voltage effects, then signal transmission accuracy is improved, but circuit size increases
Solution Approach 1:
The patent changes the parameter of common mode voltage generation from being transformer-coupled to being power-supply-referenced. By generating the common mode voltage directly from the power supply voltages (VDD1 and VDD2) rather than through transformer coupling, the patent achieves common mode suppression without adding bulky transformer-based compensation circuits.
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
Prevents signal transmission errors by effectively canceling out common mode voltage effects without enlarging the circuit, allowing accurate data reproduction.
Implementation Method 1
a primary coil through which a transmission signal from a transmitting circuit operates and a secondary coil having a center tap to which a specified voltage is supplied from an external terminal are magnetically coupled
Data Source
AI summary
Provided is a receiving circuit that operates in a power supply system different from a transmitting circuit outputting a transmission signal and receives the transmission signal through an AC coupling device where a primary coil through which the transmission signal flows and a secondary coil having a center tap to which a specified voltage is supplied from an external terminal are magnetically coupled, which includes a pulse width amplifier circuit that holds pulse signals appearing at both ends of the secondary coil for a specified period of time and outputs them as hold signals, respectively, and a differential amplifier that compares a voltage of the hold signal and a voltage of the hold signal and outputs a comparison result.