Single-Rail Switching Regulator for Wide Battery Voltage Range
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Solution Overview
Problem
Current power management units (PMUs) are limited to a minimum battery voltage of 2.7 V due to the use of 1.8 V gate oxide (GOx) devices, requiring a floating rail architecture and a separate fixed rail for different voltage needs, lacking a single-rail architecture capable of providing both floating and fixed voltages across a wide battery voltage range.
Innovation Solution
A single-rail switching regulator with a split-rail reference generator, current-sinking buffer, and fast-transient current-sink to generate both floating and fixed-rail voltages, using a high-side switching transistor with 1.8 V GOx, enabling continuous operation from 1.6 V to 4.8 V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a floating rail architecture is used with 1.8 V GOx devices, then the gate-to-source voltage across the GOx is limited to 1.8 V, but the minimum battery voltage is limited to 2.7 V
Solution Approach 1:
The patent segments the power rail system into two independent rails: a floating rail (VSSHV) that tracks battery voltage minus 1.8V for GOx protection, and a fixed rail (VDD) that provides stable 1.8V for digital devices. This segmentation allows each rail to independently satisfy its voltage requirements without constraining the battery voltage range.
Solution Approach 2:
The patent introduces an intermediary fixed-rail generator that converts the floating rail voltage into a stable fixed voltage through voltage regulation. This intermediary mechanism enables the system to provide both floating voltage protection and fixed voltage stability simultaneously, resolving the contradiction between voltage limitation and adaptability.
2Reliability
If a separate fixed rail is provided for digital devices, then digital devices receive stable 1.8 V, but the system requires a second separate fixed rail in addition to the floating rail
Solution Approach 1:
The patent merges the fixed-rail generation function into the existing floating-rail architecture by introducing a fixed-rail generator that derives its input from the floating rail. This consolidation reduces the system from requiring two completely independent power rail systems to one integrated system with dual-rail output, simplifying the overall device complexity while maintaining stable voltage supply.
3Duration of action of moving object
If 1.8 V GOx devices are used, then continuous operation is enabled, but process limitations prevent use of 2.5V GOx and 1.8V GOx devices in the same die
Solution Approach 1:
The patent creates a universal power management architecture that can accommodate different transistor types and voltage requirements through a single integrated system. The floating rail generator adapts to provide appropriate voltage levels based on the specific transistor GOx requirements, while the fixed rail provides stable operation for digital devices, enabling continuous operation across various process nodes without requiring separate dedicated circuits for each transistor type.
Data Source
AI summary
A single-rail switching regulator and method are provided. The switching regulator includes a split-rail reference generator coupled between a battery voltage (VBAT) and ground, and including a floating-rail generator to generate a floating-rail reference voltage (VSSHV_REF), a fixed-rail generator to generate a fixed-rail reference voltage (VDD_REF), a current-sinking (I-sink) buffer to receive VSSHV_REF and generate a floating-rail voltage on a floating-rail to power logic devices formed on an IC with the switching regulator, and a high-side switching transistor including a source and drain coupled between VBAT and ground, and a gate coupled to the floating-rail. The floating-rail reference generator is operable to generate a VSSHV_REF equal to VBAT−1.8V for VBAT between 1.8 and 4.8V, and 0V for VBAT less than 1.8V. The switching regulator further includes a low drop out regulator operable to receive VDD_REF and power digital devices formed on the IC using a fixed voltage.