MOSFET Voltage Reference for Temperature Insensitive SoC Integration
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Solution Overview
Problem
Conventional voltage references using parasitic bipolar junction transistors are highly susceptible to Single Event Latchup (SEL) and cannot be integrated with other ICs, making them inappropriate for System-on-Chip (SoC) realizations and sensitive to temperature and power supply variations.
Innovation Solution
A method using a circuit with a first and second MOS transistor, where the difference between their threshold voltages is compensated by a parameter representative of the operating temperature, providing a temperature-insensitive voltage reference, and incorporating an amplifier for improved power supply noise immunity and radiation hardening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parasitic BJT-based voltage reference is used, then voltage reference function is achieved, but the circuit becomes highly susceptible to SEL and cannot be integrated with other ICs
Solution Approach 1:
The patent changes the fundamental parameter of transistor type from parasitic BJT to MOSFET, which inherently eliminates the SEL susceptibility associated with BJT structures while enabling full integration with standard CMOS IC fabrication processes
Solution Approach 2:
The patent substitutes the BJT-based voltage reference mechanism with a MOSFET-based mechanism, replacing a structure that is prone to SEL with one that is inherently radiation-hardened and suitable for integrated circuit implementation
2Reliability
If conventional BJT-based voltage reference is used, then voltage reference is provided, but it manifests as a separate IC and cannot be integrated
Solution Approach 1:
The patent merges the voltage reference function with the main IC by using standard MOSFETs that are already part of the CMOS fabrication process, eliminating the need for separate ICs and enabling true System-on-Chip integration
3Temperature
If MOS transistors with different threshold voltages are used, then temperature compensation is achieved, but circuit complexity increases
Solution Approach 1:
The patent employs MOSFETs operating in the subthreshold region that automatically self-compensate for temperature effects through their inherent electrical characteristics, eliminating the need for complex external compensation circuits
Solution Approach 2:
The patent exploits the temperature-dependent parameters of MOSFETs in subthreshold operation, where the threshold voltage and current characteristics naturally provide temperature compensation without additional circuitry
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 achieves a voltage reference that is insensitive to temperature and power supply variations, reducing SEL effects and enabling integration with other ICs, thus suitable for space applications and SoC realizations.
Implementation Method 1
Temperature insensitivity is obtained by compensating a difference between the first threshold voltage and the second threshold voltage with a parameter representative of the present operating temperature
Data Source
AI summary
A method for providing a voltage reference at a present operating temperature in a circuit is provided. The circuit comprises a first MOS transistor having a first threshold voltage; and a second MOS transistor having a second threshold voltage different from the first threshold voltage is provided. Temperature insensitivity is obtained by compensating the difference between the first threshold voltage and the second threshold voltage with a parameter representative of the present operating temperature.