High-Side Current Sense Amplifier With Chopping and Fast Level Shifter
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Solution Overview
Problem
Current high-side current sense circuits face challenges with high common-mode rejection ratios (CMRR) and voltage offsets, and high-voltage level shifters experience time delays and inefficiencies, particularly in small electronics where precision and power consumption are critical.
Innovation Solution
A high-side current sensing architecture that employs a zero-drift current sensor with chopping and a switched capacitor filter, merging the VDDHV and VIP nodes to reduce complexity and power consumption, and a high-voltage level shifter with minimal clock delay, utilizing a single node for both connections and eliminating the need for precise resistor and capacitor matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser-trimmed resistors are used to attenuate input common-mode voltage, then CMRR is improved, but manufacturing cost increases and package size increases
Solution Approach 1:
The patent merges the common-mode attenuation function with the amplifier input stage by using the intrinsic impedance of the amplifier itself rather than external laser-trimmed resistors. This eliminates the need for separate precision resistor networks while maintaining CMRR performance, thereby reducing manufacturing cost and package size.
Solution Approach 2:
The amplifier circuit is designed to perform common-mode rejection using its own internal components and characteristics rather than relying on external precision resistors. The differential input stage inherently provides common-mode attenuation through its symmetric structure and high common-mode rejection capability, making the circuit self-sufficient.
2Measurement precision
If laser-trimmed resistors are used to balance inputs, then CMRR is improved, but power consumption increases
Solution Approach 1:
The patent combines the common-mode attenuation function with the amplifier's input stage, eliminating external resistor networks that would consume power. The intrinsic impedance of the amplifier provides the necessary attenuation without requiring additional power-hungry precision components.
3Measurement precision
If precisely matched resistors and capacitors are used, then CMRR is improved, but package size increases
Solution Approach 1:
The patent integrates the common-mode attenuation functionality into the amplifier's input stage, eliminating the need for external precision resistor and capacitor networks. This reduces the overall package size while maintaining CMRR performance through the amplifier's inherent differential input characteristics.
Solution Approach 2:
The patent extracts the common-mode attenuation function from external passive components and relocates it to the active amplifier stage, thereby removing the bulk external resistor networks that would increase package size.
4Measurement precision
If auto-zeroing circuitry is added to reduce offset, then voltage offset is improved, but device complexity increases
Solution Approach 1:
The patent combines offset correction functionality with the main amplification stage by using a simple differential configuration and common-mode attenuation network. This integrated approach reduces offset without requiring separate auto-zeroing circuits, thereby maintaining low complexity.
5Measurement precision
If capacitor switching is used for auto-zeroing, then voltage offset is improved, but bandwidth is reduced
Solution Approach 1:
The patent employs periodic chopping action to modulate the input signal and reject offset voltages. By switching the chopping frequency appropriately, the circuit achieves offset cancellation while maintaining high bandwidth, as the periodic action occurs at frequencies well above the signal bandwidth of interest.
Data Source
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AI summary
A high side current sensing amplifier architecture is simplified and improved over prior art current sensing amplifier circuits by using chopping only, without requiring auto-zeroing, and by using a simpler (and faster) switched capacitor filter instead of an auto-zeroing integrator filter. Also, VIP (positive DC sense node) is merged with the VDDHV (power supply) node, such that the integrated circuit package requires only a single node (package pin) to accommodate both the VIP and VDDHV connections for the current sensing amplifier circuit, resulting in being able to use a smaller integrated circuit package. A small resistor is coupled between VIP and VDDHV to reduce the offset considerably. A low latency time high voltage level shifter is provided which is essential for precise chopping operation.