Split N+ SCR Structure to Prevent Noise-Induced Mis-Triggering
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Solution Overview
Problem
Silicon Controlled Rectifiers (SCRs) are sensitive to noise, leading to mis-triggering and circuit malfunctions due to their susceptibility to small gate currents, which causes shunt currents and reduces noise immunity.
Innovation Solution
The design incorporates a split N+ region closest to the cathode, with an additional N+ region added just below the gate, eliminating shunt current and enhancing noise immunity by improving the sub-emitter resistance and current gain, thereby reducing sensitivity to noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SCR uses a conventional single N+ region connected to cathode, then the device structure is simple, but the noise immunity is poor and mis-triggering occurs easily
Solution Approach 1:
The single N+ region connected to cathode is segmented into multiple N+ regions (first N+ region and second N+ region). The first N+ region is connected to cathode while the second N+ region is connected to gate, creating separate current paths that prevent noise-induced mis-triggering while maintaining structural organization
Solution Approach 2:
The P region serves as an intermediary layer between the first N+ region (cathode connection) and second N+ region (gate connection). This intermediate P region structure helps isolate the gate and cathode connections, preventing direct noise coupling while maintaining the necessary electrical relationships
2Ease of operation
If the SCR has high sensitivity to gate current, then the device can be easily activated, but it becomes susceptible to noise and causes mis-triggering
Solution Approach 1:
The cathode connection is segmented into first and second N+ regions with different functions. The first N+ region handles main cathode current while the second N+ region is specifically connected to gate, separating the high-current path from the sensitive gate control path and reducing noise coupling
Solution Approach 2:
Different regions of the N+ structure are given different qualities and functions: the first N+ region optimized for cathode connection and main current handling, while the second N+ region is optimized for gate connection and control signal reception, with each region having tailored electrical characteristics for its specific function
Data Source
AI summary
A silicon controlled rectifier includes a first P region, an N− region, a second P region, and a plurality of N+ regions. The first P region is connected to an anode. The N− region is adjacent the first P region. The second P region is adjacent the N− region such that the N− region is sandwiched between the first P region and the second P region. The plurality of N+ regions are disposed within the second P region. A first N+ region of the plurality of N+ regions is connected to a cathode. A second N+ region of the plurality of N+ regions is connected to a gate.