Low-Noise Reference Voltage Distribution Circuit
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Solution Overview
Problem
Existing reference voltage distribution circuits in integrated circuits suffer from noise amplification due to long paths with high output impedance, leading to crosstalk and noise pollution among circuits, and the buffered reference voltages are not properly referred to their local grounds, affecting analog-to-digital conversion.
Innovation Solution
A multi-output voltage to current converter with a low-pass filter is used to convert a reference voltage into noise-free reference currents, which are then converted back into local reference voltages ideally referred to their noisy grounds, using a multistage CMOS amplifier and current mirror transistors to minimize noise amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a long path is used to distribute reference voltage from the bandgap block to receiving circuits, then the reference voltage can be distributed to multiple circuits, but noise and crosstalk are collected along the path due to high output impedance
Solution Approach 1:
The patent segments the reference voltage distribution into multiple independent current paths, with each path having its own buffer amplifier and current mirror circuit. This segmentation isolates noise in each path, preventing crosstalk between different receiving circuits while maintaining the ability to distribute reference voltage to multiple circuits simultaneously.
Solution Approach 2:
The patent introduces current mirror circuits as intermediary elements between the buffer amplifier and receiving circuits. These current mirrors act as isolated distribution nodes that convert voltage signals to current signals and back, providing galvanic isolation that blocks noise propagation along the distribution paths.
2Adaptability or versatility
If buffered and amplified reference voltages are distributed to receiving circuits with local grounds, then each circuit can operate independently, but the local ground noise is amplified by the amplifier feedback network
Solution Approach 1:
The patent replaces the traditional voltage-based distribution system with a current-based system. By using current mirror circuits instead of voltage amplifiers with feedback networks, the system eliminates the ground noise amplification problem while maintaining independent operation capability for each receiving circuit.
Solution Approach 2:
The patent uses current mirror circuits to create precise copies of the reference current for each receiving circuit. The current mirror topology ensures that each circuit receives an identical copy of the reference current, eliminating the need for feedback networks that would amplify ground noise, while still allowing independent operation.
3Object-affected harmful factors
If buffering and amplification circuits are built close to the bandgap voltage generation block, then the first drawback of long paths is solved, but the second drawback of ground noise amplification remains
Solution Approach 1:
The patent replaces voltage amplification with current mirroring in the circuits placed close to the bandgap block. The current mirror-based distribution network eliminates ground noise amplification while maintaining low output impedance, solving both the crosstalk problem and the ground reference accuracy problem simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces noise in the reference voltages distributed to each circuit, ensuring they are accurately referred to their local grounds, thereby improving the precision and cleanliness of analog-to-digital conversions without increasing area or power consumption.
Implementation Method 1
A multi-output voltage to current converter with a low-pass filter is used to convert a reference voltage into noise-free reference currents
Implementation Method 2
A multi-output voltage to current converter with a low-pass filter is used to convert a reference voltage into noise-free reference currents
Implementation Method 3
which are then converted back into local reference voltages ideally referred to their noisy grounds, using a multistage CMOS amplifier and current mirror transistors
Data Source
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AI summary
A low-noise reference voltages distribution circuit (10) is disclosed, comprising a multi-output voltage to current converter (V/I_Conv) adapted to receive an input reference voltage (VR) for providing a plurality of output reference currents (I1,...,IN) to be converted into a plurality of local reference voltages (VO1,..., VON) at corresponding receiving circuits (LCR1,...,LCRN) adapted to be connected to said reference voltages distribution circuit (10). The multi-output voltage to current converter (V/I_Conv) comprises: - an input section (20) adapted to generate on the basis of said input reference voltage (VR) a reference current (I0), the input section (20) comprising a current mirror input transistor (M0E) having a voltage controlled input terminal (g0E); - an output section (50) comprising a plurality of current mirror output transistors (M01,...,M0N) each adapted to provide a corresponding output reference current of said plurality of reference currents (I1,..., IN), each of said current mirror output transistors (M01,...,M0N) comprising a voltage controlled input terminal (g01,...,g0N), the output section (50) comprising a common input node (51) to which voltage controlled input terminals (g01,...,g0N) of said current mirror output transistors (M01,...,M0N) are connected. The voltage to current converter (V/I_Conv) comprises a low-pass filter (30) having an input node (31) connected to said voltage controlled input terminal (g0E) of the current mirror input transistor (M0E) and an output node (33) connected to said common input node (51).