Unit Cell DAC Reconfiguration for PAM3/PAM4 PSD Compliance
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Solution Overview
Problem
Existing DACs struggle to meet PSD mask requirements in both PAM3 and PAM4 modes due to the generation of triangular waveforms, which result in excessive out-of-band energy and EMC performance issues.
Innovation Solution
A unit cell-based DAC that operates in N consecutive phases with M transitions, where M is less than N, and is reconfigurable to switch between PAM3 and PAM4 modes, using monotonic transitions and equal unit cell activation in each phase to generate trapezoidal waveforms that meet PSD mask requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional DACs are used to generate waveforms in PAM3 and PAM4 modes, then the waveform generation is simple, but the out-of-band energy is excessive and PSD mask requirements are not met
Solution Approach 1:
The DAC operation is segmented into N consecutive phases with M transitions per phase. Each phase activates a specific subset of unit cells to generate controlled waveform segments that collectively form trapezoidal waveforms, reducing out-of-band energy compared to conventional continuous transitions.
Solution Approach 2:
The DAC employs dynamic reconfiguration of unit cell interconnections to switch between PAM3 and PAM4 modes. The unit cells are dynamically activated and deactivated in specific patterns during N phases with M transitions to generate trapezoidal waveforms that meet PSD mask requirements in both modes.
2Adaptability or versatility
If the DAC is made reconfigurable to support both PAM3 and PAM4 modes, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The same unit cell array is designed to perform multiple functions by reconfiguring interconnections. The DAC can operate in both PAM3 mode (converting two-bit input to three-level output) and PAM4 mode (converting two-bit input to four-level output) using the same physical unit cells, achieving multi-functionality without duplicating hardware.
Solution Approach 2:
The interconnections between unit cells are made dynamically reconfigurable through switching elements that can connect unit cells in different patterns. This dynamic reconfiguration allows the system to adapt between PAM3 and PAM4 modes by changing the activation sequence and interconnection topology without permanent hardware changes.
3Manufacturing precision
If more unit cells are activated to improve signal quality in both modes, then the output quality is improved, but the power consumption increases
Solution Approach 1:
Instead of activating all unit cells continuously, the invention activates only the necessary subset of unit cells during each phase. With N phases and M transitions, only M unit cells are activated at any given time, providing sufficient signal quality for both PAM3 and PAM4 modes while consuming less power than full-activation approaches.
Solution Approach 2:
The unit cells are activated in periodic phases rather than continuously. The N-phase operation with M transitions creates a periodic activation pattern where unit cells are turned on and off in a systematic sequence, reducing average power consumption while maintaining signal quality through coordinated periodic activation.
Data Source
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AI summary
There is disclosed a unit cell-based DAC configured to operate in N consecutive phases, wherein the unit cell-based DAC comprises a plurality of unit cells and wherein a single transition between a first state and a second state of the unit cell-based DAC is caused by M transitions of the plurality of unit cells between corresponding first states and second states, where M is smaller than N, wherein each transition of a unit cell is configured to occur during one of the N phases and wherein the interconnections of the unit cells are reconfigurable such that the unit cell-based DAC is configured to switchably operate in one of a PAM3 mode, in which the unit cell-based DAC converts a two-bit input signal into a three-level output signal, and a PAM4 mode in which the unit cell-based DAC converts the two-bit input signal into a four-level output signal.