Series-Connected Electrostatic Protection Circuit with Thyristor
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Solution Overview
Problem
Existing electrostatic protection circuits for semiconductor integrated circuit devices face challenges in accurately preventing breakdown during power-on and prolonged normal operation, and in preventing all surge current from flowing into the protection circuit during ESD immunity testing, often requiring additional resistance elements that increase chip size and risk transistor deterioration.
Innovation Solution
A series-connected electrostatic protection circuit utilizing a thyristor with a small leakage current and other circuit blocks with bipolar or MOS transistors, along with zener diodes and resistance elements, to set a high hold voltage without parallel resistance elements, and incorporating an overvoltage detection circuit and delay mechanism to control current flow during ESD testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parallel resistance elements are connected to circuit blocks to equalize source-drain voltage, then breakdown prevention accuracy is improved, but chip area increases
Solution Approach 1:
The patent extracts and eliminates the parallel resistance elements from the circuit configuration. By using series-connected circuit blocks with inherently different leakage currents, the invention removes the need for additional parallel resistors that were previously required to equalize voltages, thereby reducing chip area while maintaining breakdown prevention accuracy.
Solution Approach 2:
The invention changes the configuration from parallel to series connection of circuit blocks. This parameter change in the circuit topology fundamentally alters how voltages are distributed across blocks, allowing the system to achieve voltage equalization through the natural leakage current differences of the blocks rather than requiring additional parallel resistance elements.
2Reliability
If all surge current flows into the protection circuit during ESD testing, then ESD protection function is achieved, but the protection transistors may break down or deteriorate
Solution Approach 1:
The protection circuit is segmented into multiple series-connected circuit blocks, each with different leakage currents. This segmentation allows the surge current to be distributed and managed across multiple blocks during ESD events, preventing any single transistor from bearing the full stress of the discharge current while maintaining effective ESD protection.
Solution Approach 2:
The invention utilizes the dynamic characteristics of transistors with different leakage currents to adaptively manage current distribution. During normal operation, the different leakage currents establish appropriate voltage distribution, while during ESD events, the dynamic response of each block helps distribute the surge current, protecting individual transistors from breakdown.
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 configuration accurately prevents breakdown and deterioration of the protected circuit, reduces chip size by eliminating the need for voltage division resistors, and ensures that only necessary current flows during ESD testing, enhancing the reliability and miniaturization of the protection circuit.
Implementation Method 1
At least one circuit block out of the plurality of circuit blocks includes a thyristor having an anode connected to one end of the at least one circuit block and a cathode connected to another end of the at least one circuit block, and when a potential of a first node is higher than a potential of a second node during normal operation, a voltage between both ends of the other circuit blocks out of the plurality of circuit blocks is smaller than a voltage between the anode and the cathode of the thyristor.
Implementation Method 2
other circuit blocks may include a bipolar transistor, a MOS transistor, a zener diode, or a resistance element
Data Source
AI summary
This electrostatic protection circuit enables a high hold voltage to be set, and acts to accurately prevent breakdown of a protected circuit immediately after power on, and to prevent breakdown or deterioration of a protection device during prolonged normal operation, without connecting a resistance element in parallel to a plurality of circuit blocks connected in series. This electrostatic protection circuit is provided with a plurality of circuit blocks connected in series between a first node and a second node, at least one circuit block out of the plurality of circuit blocks including a thyristor having an anode connected to one end of the at least one circuit block and a cathode connected to the other end of the at least one circuit block. When the potential of the first node is higher than the potential of the second node during normal operation, the voltage between both ends of the other circuit blocks out of the plurality of circuit blocks is smaller than the voltage between the anode and the cathode of the thyristor.