Reference Current Source Circuit Fuse Trimming Control
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Solution Overview
Problem
Existing reference current source circuits for semiconductor integrated circuits face challenges in accurately measuring characteristics after fuse trimming, leading to potential defects due to incorrect trimming and extra consumption current, and require external signals for maintaining the trimmed state.
Innovation Solution
A reference current source circuit with a switching circuit and control circuit that connects and disconnects the current source from a trimming fuse based on input signals, allowing for measurement of semiconductor integrated circuit characteristics after trimming without external signal supply and minimizing extra current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a monitoring device with resistor and capacitor is used to predict characteristic unevenness before fuse disconnection, then measurement capability is provided, but measurement precision deteriorates due to prediction errors and inability to detect subtle characteristic errors
Solution Approach 1:
The patent applies preliminary action by measuring the characteristic unevenness of the semiconductor integrated circuit before fuse disconnection through the control circuit. The control circuit measures the voltage level at the control node, which reflects the actual characteristic unevenness including subtle errors, enabling accurate prediction of post-disconnection state without relying on imperfect monitoring devices
2Stability of the object's composition
If extra current flows through resistor Rx to maintain trimmed state without external signals, then state maintenance capability is improved, but energy consumption increases due to extra consumption current
Solution Approach 1:
The patent applies self-service by designing the control circuit to automatically maintain the trimmed state through its inherent structure. The control node voltage level self-maintains the switch state without requiring external signals or continuous current flow through additional resistors. The circuit uses the existing control node capacitance and voltage level to sustain the trimmed state, eliminating extra consumption current while preserving state stability
3Measurement precision
If two switching circuits are used to measure state with and without fuse disconnection, then measurement capability is improved, but device complexity increases due to additional circuit elements
Solution Approach 1:
The patent applies universality by designing a single control circuit that performs multiple functions: it measures the characteristic unevenness before fuse disconnection, determines the appropriate trim state, and maintains the trimmed state after disconnection. The control node and control circuit serve as a universal measurement and control mechanism, eliminating the need for separate switching circuits while providing comprehensive measurement capability
4Measurement precision
If external signals are required to maintain trimmed state, then control precision is improved, but ease of operation deteriorates due to continuous external signal supply requirement
Solution Approach 1:
The patent applies self-service by enabling the control circuit to autonomously maintain the trimmed state without external signal intervention. The control node voltage level, established during the measurement and trimming phase, self-sustains the switch state through the inherent circuit configuration. This eliminates the need for continuous external signal supply while maintaining precise control of the trimmed state
Data Source
AI summary
The reference current source circuit (10) is provided with a current source circuit (1), a trimming fuse (3), a switching circuit (2) which connects/disconnects the current source circuit (1) and/from the trimming fuse (3), a NAND circuit (4) which controls the operation of the switching circuit (2), and a pull-down resistor (R1) which connects one input terminal of the NAND circuit (4) to a GND terminal. The NAND circuit (4) controls the operation of the switching circuit (2) upon receipt of control signals (S1 and S2) and also in accordance with a signal of the one input terminal of the NAND circuit (4) so as to connect the current source circuit (1) to the trimming fuse (3). This arrangement makes it possible to measure characteristics of a semiconductor integrated circuit after fuse trimming. In addition, it is possible to maintain the state after fuse trimming without the supply of a signal from outside. Moreover, a reference current source circuit which does not consume extra consumption current is realized.