Series-Diode ESD Protection for Accurate Capacitance Sensing
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Solution Overview
Problem
Existing IC tags with capacitance sensors face errors in capacitance detection due to electromagnetic wave noise, which accumulates charges and deviates from the specified initial charge, affecting the output of internal circuits.
Innovation Solution
An electrostatic breakdown protection circuit with a series diode configuration is implemented, increasing the threshold voltage for current flow and preventing electromagnetic wave noise from accumulating charges in the external terminal, thereby reducing detection errors in capacitance sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard ESD protection circuit with single diodes is used, then electrostatic discharge protection is provided, but electromagnetic wave noise causes charge accumulation in the external terminal leading to capacitance detection errors
Solution Approach 1:
The protection circuit is segmented into multiple diodes (first diode and second diode in series for positive voltage protection, third diode and fourth diode in series for negative voltage protection) instead of using a single diode. This segmentation increases the threshold voltage for current flow, preventing electromagnetic wave noise from causing charge accumulation while maintaining ESD protection capability
Solution Approach 2:
The circuit parameters are changed by increasing the number of diodes in series, which raises the forward voltage threshold. This parameter change allows the circuit to distinguish between harmful ESD surges (which exceed the higher threshold) and benign electromagnetic noise (which remains below the threshold), thereby preventing false charge accumulation during normal operation
2Measurement precision
If the threshold voltage for current flow is increased using series diode configuration, then electromagnetic wave noise is suppressed, but the circuit complexity increases
Solution Approach 1:
The series diode configuration serves multiple functions simultaneously: it provides ESD protection for both positive and negative voltage surges, blocks electromagnetic wave noise, and maintains signal integrity for capacitance detection. This multi-functionality justifies the increased component count by delivering comprehensive protection without requiring separate circuits for each function
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
The solution effectively suppresses the accumulation of electromagnetic wave noise-induced charges, maintaining accurate capacitance detection and reducing output errors in IC tags with capacitance sensors.
Implementation Method 1
a current accompanying electrostatic discharge flows into the first or second diode of the ESD protection circuit
Implementation Method 2
electromagnetic wave noise may enter the electrode pad via the external terminal of the IC tag
Implementation Method 3
the surge voltage is clamped to [power supply voltage+forward voltage of diode] or [ground voltage-forward voltage of diode] by the ESD protection circuit
Implementation Method 4
the capacitance of the capacitor decreases and the impedance increases
Implementation Method 5
when the ambient temperature reaches the melting point of the wax, the wax filled between the electrodes of the capacitor is liquefied
Data Source
AI summary
An electrostatic breakdown protection circuit and a capacitance sensor device are provided. An electrostatic breakdown protection circuit included in an electronic device including an external terminal and an internal circuit connected to the external terminal includes: a first series diode group in which n diodes including a first diode having an anode connected to the external terminal and a second diode having a cathode applied with a power supply voltage are connected in series; and a second series diode group in which n diodes including a third diode having a cathode connected to the external terminal and a fourth diode having an anode applied with a ground voltage are connected in series.