CMOS Phase Interpolator with DLL for Clean SerDes Clock Waveforms
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Solution Overview
Problem
High-speed integrated circuits face challenges in producing clean, symmetric output waveforms due to noisy and distorted input signals, which degrade with increased frequency, affecting the quality of differential signals and eye diagram fidelity.
Innovation Solution
A CMOS phase-interpolator circuit is implemented with a delay-lock loop and SR latch, using a single phase interpolator core to reduce power consumption and improve signal quality by interpolating clock signals and synthesizing frequency and phase, while incorporating multiplexers and a clock data recovery device to enhance data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If operating frequency is increased to achieve higher speed communication, then productivity is improved, but signal quality and eye diagram fidelity deteriorate due to noisy and distorted signals
Solution Approach 1:
A phase interpolator circuit is introduced as an intermediary component between the noisy input signals and the output driver. The phase interpolator includes a delay-locked loop (DLL) with multiple delay stages that can selectively delay clock signals to generate clean, phase-adjusted output signals. This intermediary structure filters out noise and distortion from the input signals while maintaining the high operating frequency required for fast communication.
Solution Approach 2:
The invention changes the phase parameter of clock signals dynamically using the phase interpolator. By adjusting the phase shift amount through the delay stages, the system can optimize signal quality at different operating frequencies. The phase interpolator generates output clock signals with desired phase relationships, transforming the noisy input signals into clean waveforms with controlled phase and frequency characteristics.
2Reliability
If traditional phase interpolator circuits are used to improve signal quality, then reliability is improved, but power consumption increases due to multiple interpolator cores
Solution Approach 1:
The invention merges the functionality of multiple phase interpolator cores into a single phase interpolator core. The unified phase interpolator serves multiple receivers by generating phase-adjusted clock signals that are distributed to different channels. This consolidation eliminates redundant circuitry and reduces overall power consumption while maintaining the ability to provide clean, phase-controlled signals to all receivers simultaneously.
Solution Approach 2:
The single phase interpolator core is designed with universal functionality to serve multiple receivers and channels. It can generate multiple phase-shifted clock signals that are distributed to different receivers, allowing one interpolator to perform the work of multiple interpolators. This multi-functional design reduces power consumption while maintaining signal quality across all channels.
3Adaptability or versatility
If asymmetric differential signals with amplitude variation are input to achieve adaptability, then versatility is improved, but output waveform quality deteriorates
Solution Approach 1:
The delay-locked loop incorporates feedback mechanisms that monitor the phase and frequency of input signals and automatically adjust the delay stages to generate symmetric output waveforms. The feedback control ensures that despite variations in input signal quality, the output clock signals maintain consistent phase relationships and symmetry, producing clean eye diagrams with centered crossing points.
Solution Approach 2:
The phase interpolator performs preliminary processing of clock signals before they reach the output driver. By pre-adjusting the phase and generating clean, phase-aligned clock signals in advance, the system ensures that the output driver receives high-quality input signals regardless of the quality of the original input signals. This preliminary action prevents waveform distortion and maintains symmetry throughout the signal chain.
Data Source
AI summary
The present invention relates generally to integrated circuits. More particularly, the present invention provides a circuit and method for regulating a voltage for a high speed serializer/deserializer (SerDes) device. But it will be recognized that the technique can be used for regulating memory devices (e.g., DDR 4 SDRAM devices, DDR4 register devices, DDR4 controller devices), and other high speed data applications. In various embodiments, phase-interpolator is implemented in conjunction with a delay-lock loop (DLL) and an SR latch, where one or more outputs of the DLL is used by the SR latch. Additionally, such techniques can be used for a variety of applications such as network and/or computer storage systems, computer servers, hand held computing devices, portable computing devices, computer systems, network appliances and/or switches, routers, and gateways, and the like.