Semiconductor Device Switch Group Impedance Matching
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Solution Overview
Problem
Existing semiconductor devices with multiple sensors face issues with unintentional signal generation due to source voltage variations, leading to error detection, particularly in position detection systems using loop coils and battery pack voltage detection circuits.
Innovation Solution
A semiconductor device design featuring a differential amplifier configuration with two switch groups and a dummy impedance circuit, where the number of switches in each group is equal, allowing for the selection of either sensor signals or a reference voltage, thereby equalizing impedance and suppressing unintentional signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single switch group is used to select between sensor signals and reference voltage, then the device complexity is reduced, but source voltage variations cause unintentional signal generation and detection errors
Solution Approach 1:
The patent divides the switch group into two separate switch groups (first switch group and second switch group), each responsible for one input terminal of the differential amplifier. This segmentation allows independent control of voltage variations at each terminal, preventing the propagation of source voltage variations that would otherwise cause detection errors.
Solution Approach 2:
The patent introduces a dummy impedance circuit with adjustable impedance value to balance the impedance between the two input terminals of the differential amplifier. By changing the impedance parameter of the dummy circuit, the system compensates for impedance mismatches caused by different numbers of switches in each group, thereby suppressing unintentional signal generation while maintaining detection accuracy.
2Ease of manufacture
If different numbers of resistance elements are coupled to input terminals of the differential amplifier, then the circuit design is simplified, but source voltage variations generate unintentional signals
Solution Approach 1:
The patent uses a dummy impedance circuit with variable impedance to compensate for the difference in the number of resistance elements connected to each input terminal. By adjusting the impedance parameter, the system equalizes the effective impedance seen by the differential amplifier at both terminals, preventing source voltage variations from generating unintentional signals while maintaining the simplified circuit design.
3Reliability
If the number of switches in each switch group is made equal, then source voltage variation effects are canceled, but the device complexity increases
Solution Approach 1:
The patent segments the switch control into two independent groups, each managing one input terminal of the differential amplifier. This segmentation enables precise control over the number of switches in each group, allowing the system to achieve equal numbers of switches (thereby canceling source voltage variation effects) while maintaining manageable complexity through modular design.
Solution Approach 2:
The patent creates a symmetric copy of the switch group configuration for the second input terminal, mirroring the first switch group's structure. This copying approach ensures that both input terminals have the same number of switches, which cancels the effects of source voltage variations. The dummy impedance circuit provides the necessary flexibility to achieve this symmetry without significantly increasing overall device 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 design enhances the Power Supply Rejection Ratio (PSRR) and improves detection accuracy by canceling the effect of source voltage variations, reducing unintended signal detection and enhancing the performance of sensor systems.
Implementation Method 1
a differential amplifier which amplifies and outputs a differential voltage between two input terminals
Implementation Method 2
a first switch group which selectively outputs a signal input from the first group of sensor coupling terminals and a reference voltage, from an output terminal
Data Source
AI summary
A switch group selectively outputs a signal input from IC terminals and a reference voltage. Another switch group selectively outputs a signal input from IC terminals and a reference voltage. A differential amplifier amplifies a differential voltage between a signal output from the switch group and a signal output from the another switch group. The switch group and the another switch group include the same number of switches. When to select any of signals input from the IC terminals in the switch group, a reference voltage is selected in the another switch group. When to select any of signals input from the IC terminals in the another switch group, a reference voltage is selected in the switch group.