Band-gap Current Repeater with Localized Feedback
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Solution Overview
Problem
Existing band-gap reference signal distribution architectures in SoCs face challenges due to resistive loss in open-loop systems, leading to amplitude variations and significant errors in current repeaters, which are not effectively controlled by global feedback schemes.
Innovation Solution
A series of current repeaters with localized feedback is implemented, where each repeater generates its own feedback current to accurately duplicate and forward the reference current, reducing the impact of offset voltage and finite gain errors through differential amplifiers with parallel transistor configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a series of current repeaters is used to distribute the band-gap reference signal, then the resistive loss in amplitude is addressed and the signal is successfully distributed to distant circuit blocks, but error accumulates through the series of repeaters leading to significant deviation from the original reference signal
Solution Approach 1:
The patent implements a feedback mechanism where the output of each current repeater is fed back to its input. This feedback loop allows the repeater to detect and correct errors in the repeated signal, preventing error accumulation. The feedback signal is combined with the input signal through a summing junction, and the difference is amplified to correct the output, ensuring that each repeater maintains signal accuracy rather than propagating errors from previous stages.
2Measurement precision
If global feedback is implemented from the final repeater to the band-gap current source, then the error at the final repeater is minimized, but the local error at intermediate repeaters remains uncontrolled and may be unacceptably high
Solution Approach 1:
The patent divides the single global feedback system into multiple localized feedback loops, with each current repeater having its own independent feedback mechanism. This segmentation allows each repeater stage to independently control and correct its own local errors, rather than relying on a single global feedback loop that only addresses the final output. Each segment (repeater) maintains its own feedback loop to the band-gap current source, ensuring local accuracy throughout the entire distribution network.
3Measurement precision
If each band-gap reference circuit is provided for each circuit block, then each block has its own independent reference signal, but the cost increases due to requirements for off-chip resistors, die space, and power consumption
Solution Approach 1:
The patent merges multiple band-gap reference circuits into a single shared band-gap reference circuit that serves all circuit blocks. Instead of having separate reference circuits for each block, one master reference circuit generates a reference current that is then distributed to multiple repeaters, each serving different circuit blocks. This consolidation eliminates the need for multiple off-chip resistors, reduces die space requirements, and lowers power consumption while maintaining reference signal availability across all blocks through the distributed repeater architecture.
Data Source
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AI summary
A series of current repeaters with localized feedback is provided. Each current that precedes a subsequent current repeater in the series is configured to receive a feedback current from the subsequent current repeater and generate an error signal accordingly with a differential amplifier so as to reduce current repetition errors that would otherwise result from an offset voltage in the differential amplifier.