Shared Capacitor Voltage Regulator Area Reduction
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Solution Overview
Problem
On-chip voltage regulators require significant area due to large filter and stability capacitors, and conventional solutions that reuse capacitors between different voltage regulators either require large switches or reduce capacitor effectiveness, leading to inefficiencies in area reduction and performance.
Innovation Solution
The integrated circuit design shares a single capacitor between two voltage regulators using switches located between the capacitor and ground, allowing for efficient switching and inversion of capacitor plates to maintain performance without increasing area, using CMOS switches to reduce switch size and enable full power supply utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitors are duplicated for two voltage regulators, then each regulator has sufficient capacitance for stable operation, but the total area occupied by capacitors doubles
Solution Approach 1:
The patent merges the capacitor resources of two voltage regulators into a single shared capacitor. The first and second voltage regulators both connect to the same capacitor, allowing one capacitor to serve the filtering and stability functions for both regulators, thereby reducing the total capacitor area while maintaining operational reliability
Solution Approach 2:
The shared capacitor performs multiple functions: it serves as the filter capacitor for both the first and second voltage regulators, and through the switching mechanism, it can be dynamically allocated to either regulator as needed. This multi-functionality allows a single capacitor to replace what would traditionally require two separate capacitors
2Area of stationary object
If traditional series switches are used to share capacitors between voltage regulators, then capacitor duplication is avoided, but the switch size becomes comparable to the capacitor size, negating area benefits
Solution Approach 1:
The patent introduces a control circuit as an intermediary that manages the switching between voltage regulators. This control circuit receives signals from both regulators and selectively activates either the first or second switch based on which regulator is currently active, enabling efficient capacitor sharing without requiring oversized switches
3Area of stationary object
If transistors are used as series switches to share capacitors, then capacitor area is reduced, but a zero is created in the transfer function, significantly reducing effective capacitance
Solution Approach 1:
The patent extracts the problematic zero-introducing element (the series transistor switch) from the signal path. Instead of placing switches in series between the capacitor and the regulator circuit where they would create zeros in the transfer function, the design reconfigures the switching to occur at the capacitor plates, separating the switching function from the critical signal path that determines effective capacitance
Data Source
AI summary
In one embodiment, an integrated circuit (e.g., FPGA) has two voltage regulators sharing stability and filter capacitors. A switch is located between each plate of each capacitor and a common voltage reference (e.g., ground) such that one of the two voltage regulators can be selectively connected to ground via the stability and filter capacitors.