Overcurrent Detector for Multi-Channel Level Shifter Module
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Solution Overview
Problem
Conventional overcurrent detection circuits in multi-channel level shifter modules suffer from mismatched overcurrent levels due to variations in electronic components, leading to increased layout area and reduced consistency, primarily because of the use of laterally diffused metal-oxide semiconductor (LDMOS) transistors which occupy more space and have greater device characteristic mismatches compared to ordinary MOSFETs.
Innovation Solution
The proposed overcurrent detector incorporates a plurality of current sensing units and overcurrent determination units, each paired with a common voltage level transition circuit, utilizing ordinary MOSFETs to minimize layout area and enhance consistency by outputting a unified indication signal when current exceeds a predefined level, thereby reducing the number of LDMOSes required and improving overcurrent level matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LDMOS transistors are used in overcurrent detection circuits, then high voltage operation is achieved, but layout area increases and device characteristic mismatch increases
Solution Approach 1:
The circuit is divided into two distinct voltage domain sections: a high-voltage section (current sensing unit with LDMOS) and a low-voltage section (overcurrent determination unit with ordinary MOSFETs). The LDMOS transistor is used only where high voltage is required for current sensing, while the determination logic operates at low voltage with ordinary MOSFETs, thereby minimizing the number of LDMOS devices and reducing overall layout area while maintaining high voltage operation capability.
Solution Approach 2:
A voltage level transition unit acts as an intermediary between the high-voltage current sensing unit and the low-voltage overcurrent determination unit. This intermediary converts the high-voltage sensed signal to a low-voltage signal, enabling the use of ordinary MOSFETs in the determination logic while preserving the ability to detect high-voltage overcurrent conditions through the LDMOS-based sensing circuit.
2Reliability
If LDMOS transistors are used in overcurrent detection circuits, then high voltage operation is achieved, but device characteristic mismatch increases
Solution Approach 1:
The circuit segregates functions by voltage domain: LDMOS transistors are confined to the high-voltage current sensing unit where their high voltage capability is essential, while ordinary MOSFETs are used in the low-voltage overcurrent determination unit where better matching characteristics are needed. This segmentation ensures that LDMOS devices are only used where absolutely necessary, minimizing their impact on overall circuit matching.
Solution Approach 2:
The voltage level transition unit serves as an intermediary that isolates the high-voltage LDMOS sensing circuit from the low-voltage determination logic. By converting the sensed signal voltage level, it allows the determination unit to use ordinary MOSFETs with better matching characteristics, thereby reducing device characteristic mismatch while maintaining high voltage operation capability in the sensing portion.
3Reliability
If separate overcurrent detection circuits are implemented for each level shifter channel, then individual channel protection is achieved, but circuit complexity and component count increase
Solution Approach 1:
Multiple current sensing units that detect overcurrent conditions in different level shifter channels are merged into a single integrated overcurrent detection circuit. The sensing units for multiple channels share common components including the voltage level transition unit and the overcurrent determination unit, thereby achieving individual channel protection while reducing overall circuit complexity and component count compared to fully separate detection circuits.
Data Source
AI summary
An overcurrent detector for multiple level shifter circuits includes an overcurrent detecting circuit that senses currents acquired through level shifter circuits, and that outputs an indication signal indicating occurrence of overcurrent when one of the currents sensed thereby is greater than a predefined current level.