Transition Density Equalization Circuit for Power Supply Noise
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Solution Overview
Problem
High-speed integrated circuits face significant challenges with power supply noise, particularly noise-induced jitter on clock signals and delay paths, which existing solutions like bypass capacitance and constant current drivers are inadequate in addressing due to limitations in filtering high-frequency noise and increased costs or power consumption.
Innovation Solution
A system that includes an additional transition circuit configured to transition according to a data stream, mimicking the primary circuit's current draw and using decision circuitry to equalize transitions, thereby shifting the frequency of power supply noise to minimize its negative effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If bypass capacitance is added to filter power supply noise, then noise filtering capability is improved, but chip area increases and cost increases
Solution Approach 1:
The patent extracts the noise filtering function from physical bypass capacitance and implements it through a digital signal processing approach using a finite impulse response (FIR) filter. The FIR filter processes the data stream to generate an equalization signal that compensates for power supply noise effects, thereby achieving noise filtering without adding physical capacitance components to the chip.
Solution Approach 2:
The patent replaces the mechanical/electrical bypass capacitance system with a digital signal processing system. Instead of using physical capacitors to filter noise, the system uses digital filtering algorithms implemented in logic circuits to achieve the same noise mitigation effect, substituting electronic filtering with computational filtering.
2Object-affected harmful factors
If on-package or on-board capacitors are used for noise filtering, then noise filtering is improved up to a few hundred megahertz, but effectiveness is limited at higher frequencies above 6 GHz
Solution Approach 1:
The patent changes the operating parameters of the filtering approach by using a digital FIR filter with adjustable tap coefficients that can be optimized for different frequency ranges. This allows the same filtering structure to effectively handle noise across a broad frequency spectrum from low frequencies up to and beyond 6 GHz, overcoming the frequency limitations of physical capacitors.
3Object-affected harmful factors
If constant current drivers are used to reduce noise effects, then noise resistance is improved, but power consumption and area on semiconductor die increase
Solution Approach 1:
The patent extracts the noise resistance function from constant current drivers and implements it through a digital equalization signal generated by an FIR filter. This approach achieves noise resistance by compensating for noise effects in the data stream rather than by fundamentally changing the driver current characteristics, thereby avoiding the high power consumption and area requirements of constant current drivers.
Data Source
AI summary
A system for equalizing transition density in an integrated circuit includes a first circuit configured to transition according to a data stream; and a second circuit configured to transition at a time when the first circuit is not transitioning.