PMOS Overcurrent Detection Circuit With Replica Threshold Stabilization
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Solution Overview
Problem
Existing overcurrent detection circuits in semiconductor integrated circuits face challenges in maintaining reliability due to temperature-dependent variations and process fluctuations, leading to inconsistent overcurrent detection thresholds and increased power consumption.
Innovation Solution
An overcurrent detection circuit that includes a voltage-current conversion circuit with a native NMOS transistor, a voltage divider circuit, and a replica PMOS transistor stacked vertically, which adjusts temperature characteristics and reduces process variations, enabling accurate overcurrent detection with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional overcurrent detection circuits are used, then overcurrent detection function is provided, but temperature-dependent variations and process fluctuations cause unreliable detection thresholds
Solution Approach 1:
The patent employs a replica transistor that copies the electrical characteristics of the high-side transistor. By mirroring the transistor structure and operating conditions, the detection circuit compensates for process variations and temperature effects, maintaining reliable threshold detection despite environmental changes.
Solution Approach 2:
The patent adjusts the gate voltage of the replica transistor dynamically to compensate for temperature-dependent variations. By changing the voltage parameter in response to temperature changes, the detection threshold remains stable across different operating conditions, eliminating the harmful effects of thermal drift.
2Measurement precision
If high-precision overcurrent detection is implemented, then detection accuracy is improved, but power consumption increases
Solution Approach 1:
The overcurrent detection circuit operates autonomously by comparing the voltage drop across the high-side transistor with the replicated characteristics. The replica transistor self-adjusts its operating point to match the main transistor, eliminating the need for external reference circuits or continuous calibration, thereby achieving high precision with minimal power overhead.
Solution Approach 2:
The detection circuit operates in a periodic manner, activating the replica transistor and comparison logic only when the high-side transistor is in the on-state. This periodic operation reduces average power consumption while maintaining detection accuracy during critical switching periods.
Data Source
AI summary
A semiconductor integrated circuit includes: a high-side transistor as a PM OS transistor; and an overcurrent detection circuit comparing a current flowing the high-side transistor with a threshold current and including: a voltage-current conversion circuit converting a reference voltage into a reference current; a replica transistor as a PM OS transistor on a path of the reference current and including a source connected to a source of the high-side transistor; and a comparator comparing drain voltages of the high-side and replica transistors, wherein the voltage-current conversion circuit includes: an input terminal receiving the reference voltage; an NM OS transistor as a native transistor; a first resistor connected between a source of the NM OS transistor and a ground; and a voltage divider circuit including second and third resistors connected in series between the input terminal and the ground, and supplying a divided voltage of the reference voltage to a gate of the NM OS transistor.