Hybrid-Coded Multi-Cell Step Circuit for Glitch-Free Switching
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Solution Overview
Problem
Binary and thermometer coded step devices suffer from signal glitches due to unequal turn ON and turn OFF times of MOSFET switches, leading to nonlinear behavior and reliability issues, while thermometer coded devices increase area, power consumption, and insertion loss.
Innovation Solution
Hybrid-coding with a multi-cell architecture that combines fixed and variable cells, allowing for selectable steps with varying ranges and resolutions, minimizing glitches and reducing the number of cells needed, thereby minimizing area, power consumption, and insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If binary coding is used in step devices, then device complexity is reduced and design is simplified, but signal glitches occur during switching due to unequal turn ON and turn OFF times
Solution Approach 1:
The patent applies preliminary action by introducing a delay element that anticipates the unequal turn-off times of MOSFET switches. The delay element is configured to hold one of the control signals for a predetermined time period, which compensates for the timing mismatch between switch turn-on and turn-off operations. This preliminary timing adjustment prevents signal glitches before they occur during the switching transition.
2Reliability
If thermometer coding is used in step devices, then signal glitches are eliminated, but area, power consumption, and insertion loss increase
Solution Approach 1:
The patent applies local quality by selectively applying the delay element only to specific control signals that require timing adjustment, rather than redesigning the entire control system. The delay element is locally inserted in the control signal path to correct the timing issue at the precise location where the glitch occurs, maintaining the compact binary coding structure while fixing the reliability problem.
3Measurement precision
If multiple MOSFET switches are used to achieve desired attenuation levels, then resolution is improved, but unequal turn ON and turn OFF times cause glitches
Solution Approach 1:
The patent introduces a delay element as an intermediary component between the control signal source and the MOSFET switches. This intermediary holds one of the control signals for a predetermined time period, mediating the timing relationship between multiple switches. The delay element acts as a buffer that coordinates the switching actions of multiple MOSFETs, ensuring they transition smoothly without causing glitches while maintaining the desired attenuation resolution.
Data Source
AI summary
Hybrid-coding, multi-cell architecture and operating techniques for step devices provide advantages over binary-coded and thermometer-coded step devices by minimizing or avoiding glitches common in the transient response of binary-coded step devices and by minimizing or avoiding significant increases or degradation in one or more of area, package dimensions, pin counts, power consumption, insertion loss and parasitic capacitance common to thermometer-coded step devices having equivalent range and resolution.