Voltage Regulator with Dual Frequency Paths for High-Speed SerDes
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Solution Overview
Problem
High-speed integrated circuits face challenges in producing clean, symmetric output waveforms due to noisy and inconsistent input signals, which degrade with increased operating frequency, leading to poor signal quality and inefficiencies in power supply noise rejection.
Innovation Solution
A voltage regulator device with a wide band amplifier and source follower, coupled with low and high frequency paths, is used to supply power to the line driver, providing a high-quality regulator output that rejects power supply noise and operates across a wide range of frequencies, utilizing CMOS technology to minimize power consumption and noise sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If operating frequency is increased to achieve higher data rates, then productivity is improved, but signal quality deteriorates due to noisy and distorted signals
Solution Approach 1:
The voltage regulator is segmented into multiple independent paths: a high-frequency path with a second transistor for rejecting high-frequency noise, and a low-frequency path with a first transistor for maintaining DC voltage stability. This segmentation allows each path to be optimized for its specific frequency range, enabling the system to maintain signal quality at high operating frequencies by effectively filtering both high-frequency and low-frequency noise components from the power supply.
2Device complexity
If conventional voltage regulator designs are used, then device complexity is kept simple, but power supply noise rejection is insufficient
Solution Approach 1:
The voltage regulator employs dynamic frequency-dependent noise rejection by implementing two separate transconductance paths with different frequency characteristics. The first transistor operates primarily at low frequencies to maintain DC stability, while the second transistor operates at high frequencies to reject switching noise and RF interference. This dynamic approach allows the regulator to adapt its noise rejection characteristics based on the frequency content of the input noise, achieving superior power supply rejection without requiring overly complex circuitry.
Data Source
AI summary
The voltage regulator device has a wide band amplifier having an input reference voltage, Vref and an input feedback voltage, Vfbk. The device has a source follower coupled to the wide band amplifier, the source follower coupled to an output of the wide band amplifier. The device has a VDD source, a regulator output, and a current source coupled to the source follower and the VDD source. The device has a low frequency path comprising a first transistor. The first transistor has a first gate, a first source, and a first drain. The first source is coupled to the VDD source. The first gate is coupled to a slow node, and the first drain is coupled to the regulator output. The low frequency path comprises a RC network, which has a capacitor, a resistor, and the slow node configured between the resistor and the capacitor. The device has a high frequency path comprising a second transistor. The second transistor has a second gate, a second source, and a second drain. The second source is coupled to the VDD source. The second gate is coupled to a fast node, and the second drain is coupled to the regulator output.