CMOS Contact Potential Drain Path for Substrate Current Inhibition
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Solution Overview
Problem
CMOS circuits in airbag ignition systems are prone to malfunction due to the formation of parasitic bipolar transistors when external connections are subjected to unintended potentials, leading to substrate currents that can cause airbag failures.
Innovation Solution
A device is implemented to monitor the potential of external contacts in CMOS circuits, comparing it to a reference value, and connect the contact to a leakage circuit node to drain current, preventing its flow into the substrate when the potential falls below the reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep n-well structures are used to protect against substrate current, then substrate protection is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention segments the substrate protection function by introducing separate contact structures (first contacts and second contacts) that are spatially distributed across the substrate. These contacts are connected to different potential lines (first potential line and second potential line) to independently manage substrate current paths, thereby protecting the substrate without requiring complex deep n-well structures throughout the entire device.
Solution Approach 2:
The invention introduces intermediary elements (the first and second contacts, and their associated potential lines) that mediate between the substrate and the harmful substrate current. These contacts act as intermediate connection points that can be selectively activated to drain substrate current away from sensitive regions, providing protection without the need for complex deep n-well structures.
2Ease of operation
If substrate current is allowed to flow, then device operation is simpler, but latch-up effects and device damage occur
Solution Approach 1:
The invention applies preliminary anti-action by pre-configuring the first and second contacts to be capable of draining substrate current before latch-up effects can occur. The contacts are positioned and connected such that they can immediately intercept and divert substrate current when it begins to flow, preventing the current from reaching critical thresholds that would cause latch-up or device damage.
Solution Approach 2:
The invention implements a feedback mechanism where the substrate potential is continuously monitored through the contact structures connected to different potential lines. When substrate current flow causes the substrate potential to shift toward levels that could trigger latch-up, the feedback through the potential lines activates the appropriate contacts to drain the current, thereby preventing harmful effects while maintaining normal device operation.
3Device complexity
If contact potential is not monitored, then device operation is simpler, but substrate current injection cannot be prevented
Solution Approach 1:
The invention performs preliminary action by pre-establishing multiple contact structures (first contacts and second contacts) connected to different potential lines before substrate current injection occurs. These contacts are positioned and configured in advance to monitor substrate potential conditions and can be selectively activated to drain substrate current, enabling prevention of substrate current injection without requiring complex real-time monitoring 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 substrate currents that could disrupt the functioning of adjacent electronic components, ensuring reliable operation of airbag ignition circuits by draining current through parasitic structures.
Implementation Method 1
a detecting circuit (30) is provided, which detects a potential of a contact (22, 23) of the integrated CMOS circuit
Implementation Method 2
connect the contact (PDH, PDL) to a leakage circuit node (ABK) to drain the current, so that it does not flow through the parasitic bipolar lateral structure
Data Source
Figure 1a
Figure 1b~1c
Figure 2
AI summary
The invention relates to various devices and methods for preventing the injection of a substrate current into the substrate sub of a CMOS circuit. For this purpose, the devices implement different methods for preventing such injection. They detect the potential of a contact (PDH, PDL) of the integrated CMOS circuit, compare the value of the detected potential with a reference value, and connect the contact (PDH, PDL) to a leakage circuit node (ABK) to drain the current, so that it does not flow through the parasitic bipolar lateral structure, i.e., not into the substrate. The leakage circuit node can be connected, for example, to the reference potential line (GND) or to another line that has a higher potential than that of the reference potential line (GND). This electrical connection is then activated or...initiated when the value of the contact potential (PDH, PDL) is below or equal to a reference value, where this reference value is below the potential of the substrate Sub and/or below the potential of the reference potential line (GND) or the other line mentioned above.