Clock Input Driver RC Filter for Edge Delay Control
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Solution Overview
Problem
Integrated circuits face challenges in ensuring proper timing specifications, filtering transient pulses, and managing edge delay spreads due to process, voltage, and temperature variations, which can lead to failure in data valid times and skew issues.
Innovation Solution
The implementation of a dual-stage RC filter in the input driver, comprising an NMOS capacitor and a PMOS capacitor, coupled between pairs of inverters, to compensate for variations in NMOS and PMOS transistors, effectively filters rising and falling edge transients and controls edge delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter is added to the input driver to filter transient pulses and control edge delays, then transient signal filtering and edge delay control are improved, but device complexity increases
Solution Approach 1:
The filter functionality is merged with the existing input driver circuit by integrating capacitive elements directly into the driver stages. The first capacitor is coupled between the first and second inverters, and the second capacitor is coupled between the second and third inverters, combining filtering and signal processing in a single integrated structure rather than adding a separate filter module.
Solution Approach 2:
The capacitive elements serve multiple functions simultaneously: they act as filters to remove transient pulses, they control rising and falling edge delays, and they compensate for process, voltage, and temperature variations. This multi-functionality reduces the need for separate dedicated circuits for each function.
2Reliability
If capacitors are added to compensate for NMOS and PMOS variations, then edge delay control is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses capacitive elements whose electrical characteristics can be adjusted to compensate for variations in transistor behavior due to process, voltage, and temperature. By changing the capacitance values and configurations, the circuit can adapt to different operating conditions and maintain consistent edge delay performance without requiring extremely tight manufacturing tolerances on individual components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures that data valid times are met, transient signals are filtered, and edge delay spreads are minimized, maintaining a controlled delay difference between rising and falling edges across process, voltage, and temperature variations.
Implementation Method 1
The filter has a first stage including an NMOS capacitor that compensates for the driver's NMOS variation
Implementation Method 2
The filter has a second stage that includes a PMOS capacitor that compensates for the driver's PMOS variation
Implementation Method 3
an interface may filter out signal features with very short delays so that such transient signal features are not treated as legitimate clock transitions or data transitions
Data Source
AI summary
An integrated circuit includes a clock input pad that receives a clock signal from an external source. The integrated circuit includes a core logic and an input driver coupled between the clock input pad and the core logic and configured to provide the clock input signal to the core logic. The input driver includes a filter including a plurality of inverter stages coupled in series. The input driver includes an NMOS capacitor coupled between a first pair of the inverter stages. The input driver includes a PMOS capacitor coupled between a second pair of the inverter stages.