Floating-Rail Reference Generator for 1.6V Low-Power Operation
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Solution Overview
Problem
Current floating-rail architectures in power management units and switching regulators are limited to operating with a minimum battery or DC input voltage of 2.7V, failing to support continuous operation across the 1.6V to 4.8V range required by modern portable devices, especially with the advancement to 28 nanometer and 22 nanometer semiconductor technologies.
Innovation Solution
A low-power floating-rail reference generator is developed, utilizing a tracking current source coupled with a current scaling resistor between the input voltage and ground, generating a floating-rail reference voltage (VSSHV_REF) through a differential amplifier-controlled pair of MOS transistors, allowing operation from 1.6V to 4.8V with a total current consumption less than 100 nano-amperes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional floating-rail architecture is used, then floating-rail voltage can be generated, but minimum operating voltage is limited to 2.7V instead of 1.6V
Solution Approach 1:
The patent implements a dynamic floating-rail voltage generation system that adapts to varying input voltages. The differential amplifier continuously adjusts the gate voltages of PMOS transistors based on the input voltage level, enabling the system to operate reliably from 1.6V to 4.8V while maintaining stable VSSHV_REF output. This dynamic adjustment resolves the contradiction by making the minimum operating voltage adaptable rather than fixed.
Solution Approach 2:
The patent changes key operating parameters including gate-source voltages (VGS1, VGS2), drain currents (ID1, ID2), and transistor dimensions to enable operation at lower input voltages. By adjusting these parameters dynamically through the differential amplifier control, the system achieves 1.6V minimum operation while maintaining voltage stability through controlled parameter relationships.
2Use of energy by moving object
If tracking current source with differential amplifier is used, then minimum operating voltage is reduced to 1.6V, but power consumption increases
Solution Approach 1:
The patent uses partial action by implementing a simplified differential amplifier that only adjusts gate voltages to the extent necessary for maintaining voltage stability. The current sources are designed to provide just sufficient current for proper operation without excessive margins, reducing power consumption while achieving the 1.6V minimum operating voltage requirement.
Solution Approach 2:
The patent optimizes power consumption by carefully selecting and dynamically adjusting parameters such as transistor dimensions, current source values, and resistor ratios. These parameter changes enable the system to achieve low-power operation (comparable to conventional designs) while operating at the lower 1.6V minimum voltage through efficient parameter matching and scaling.
3Ease of manufacture
If 1.8V Gox devices are used for both logic and power transistors, then fabrication compatibility is improved, but floating-rail voltage generation becomes complex
Solution Approach 1:
The patent achieves universality by using the same 1.8V Gox device technology for both logic and power transistors, eliminating the need for separate fabrication processes. The floating-rail reference generator circuit is designed to be multi-functional, serving both voltage reference and power management functions, thereby simplifying the overall system despite using identical device types throughout.
Solution Approach 2:
The patent introduces a floating-rail reference generator as an intermediary circuit that mediates between the 1.8V logic devices and the variable input voltage (1.6V to 4.8V). This intermediary circuit handles the voltage adaptation complexity internally, allowing the rest of the system to use simple 1.8V Gox devices without dealing with voltage variation complexity.
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
The solution provides a stable 1.8V floating-rail voltage for microcontroller units, enabling continuous operation across the 1.6V to 4.8V range while maintaining low power consumption, thus supporting modern semiconductor technologies and portable device requirements.
Implementation Method 1
a pair of MOS transistors having a first transistor coupled between the input voltage (VBAT) and the output and a second transistor, and a differential amplifier having an output coupled to gates of the first and second transistors
Implementation Method 2
generate a tracking current (Isource) through the current scaling resistor to produce a floating-rail reference voltage (VSSHV_REF)
Data Source
AI summary
A floating-rail reference generator and method of operating the same are provided. Generally, the generator includes a tracking current source coupled in series with a current scaling resistor between an input voltage (VBAT) and ground. The tracking current source is operable to receive a reference voltage and couple a tracking current through the resistor to produce a floating-rail reference voltage (VSSHV_REF) at an output between the tracking current source and scaling resistor, wherein: VSSHV_REF=((VBAT-VGS)/k)·1/R·k·R, where VGS is a desired constant potential difference between VBAT and VSSHV_REF, k is a voltage scaling ratio, and R is a resistance of the current scaling resistor. In some embodiments, the tracking current source includes a transistor coupled between VBAT and the output, and controlled by a differential amplifier.