Current Sense Amplifier Bandwidth Control for Common-Mode Transients
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Solution Overview
Problem
Current current sense amplifiers experience disturbances and glitches due to large and fast common-mode voltage transients, which can lead to improper operation, and existing solutions either ignore these transients or increase circuit area and production cost by providing symmetric signal paths.
Innovation Solution
A current sense amplifier circuit with two amplifier stages and a common-mode transient detection circuit that detects common-mode voltage transients and temporarily reduces the bandwidth of the second amplifier stage to prevent transient-induced disturbances, using a switch controlled by a common-mode transient detection circuit to maintain the output voltage before the transient occurred.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If symmetric signal paths are provided to reject common-mode transients, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent introduces a common-mode transient detector circuit as an intermediary component that senses common-mode voltage transients and generates control signals to temporarily reduce the bandwidth of the second amplifier stage. This mediator approach achieves transient rejection without requiring complex symmetric signal paths, thereby maintaining measurement precision while avoiding increased circuit complexity
Solution Approach 2:
The patent dynamically changes the bandwidth parameter of the second amplifier stage in response to detected common-mode transients. By temporarily reducing the bandwidth during transient events and restoring it during normal operation, the system achieves adaptive common-mode rejection without permanent circuit complexity increases, resolving the contradiction between measurement precision and device complexity
2Reliability
If bandwidth is reduced to prevent transient disturbances, then reliability is improved, but speed of response deteriorates
Solution Approach 1:
The patent implements periodic action by temporarily reducing bandwidth only during the specific time window when common-mode transients occur, as detected by the transient detector circuit. The bandwidth is restored to full speed after the transient event concludes. This time-dependent periodic adjustment maintains reliability during critical transient periods while preserving high-speed operation during normal conditions, resolving the contradiction between reliability and speed
Data Source
AI summary
A current sense amplifier includes a first amplifier stage, a second amplifier stage, a switch, and a common-mode transient detector. The first amplifier stage has a first amplifier output, a second amplifier output, a first amplifier input, and a second amplifier input. The second amplifier stage has a third amplifier input coupled to the first amplifier output, and a fourth amplifier input coupled to the second amplifier output. The switch has a switch control input, a first switch terminal coupled to the third amplifier input, and a second switch terminal coupled to the fourth amplifier input. The common-mode transient detector circuit has a detector output, a first detector input and a second detector input. The detector output is coupled to the switch control input. The first detector input is coupled to the first amplifier input. The second detector input is coupled to the second amplifier input.