eFuse Pull-Down Clamping for Fast Over-Current Limiting
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Solution Overview
Problem
Conventional efuse circuits face challenges in quickly reducing current during over-current events, leading to potential current overload due to the longer time required by control loops to regulate the current.
Innovation Solution
An efuse circuit comprising a switch, sample circuit, closed-loop control circuit, and pull-down circuit, where a pull-down circuit clamps the voltage across the control and output nodes to a preset value when an error signal exceeds a threshold, ensuring the current does not exceed the maximum allowable limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional control loop is used to regulate current, then the current can be regulated to a target value, but the response time is too slow causing current overload during over-current events
Solution Approach 1:
The pull-down circuit is pre-configured with a threshold voltage reference and automatically activates when the error signal exceeds the threshold, without waiting for the control loop to complete its regulation cycle. This preliminary action mechanism enables immediate current reduction upon detecting over-current conditions, resolving the contradiction between protection reliability and response speed
Solution Approach 2:
When an over-current event is detected (error signal > threshold), the pull-down circuit rapidly clamps the voltage to the threshold value, skipping the gradual regulation process of the conventional control loop. This rushing through the regulation process achieves immediate current limitation, thereby improving response speed while maintaining protection reliability
2Reliability
If the control loop regulates current slowly, then the current can be reduced to target value, but the efuse switch experiences current overload during the regulation period
Solution Approach 1:
The pull-down circuit provides beforehand cushioning by clamping the voltage to a preset threshold before current overload can occur. When the error signal exceeds the threshold, the circuit immediately limits the voltage swing, cushioning against potential current overload and protecting the efuse switch during the transient period
Solution Approach 2:
The pull-down circuit acts as an intermediary between the control loop and the efuse switch. It mediates the voltage signal by clamping it to a safe threshold level, preventing harmful voltage spikes from reaching the switch during over-current events, thus eliminating current overload while maintaining circuit protection
Data Source
AI summary
A method for controlling an efuse circuit is provided. The method includes the following steps. A sample signal of a switch is provided. An error signal is generated according to the sample signal and a reference signal. The error signal is compared with a threshold. A voltage across a control node of the switch and an output node of the switch is clamped to a preset voltage value when the error signal is greater than the threshold.