Temperature Sensor Circuit for DRAM Self-Refresh Control
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Solution Overview
Problem
Semiconductor memory devices, such as DRAM in mobile systems, face challenges in accurately controlling operation conditions due to temperature variations, leading to inefficiencies in power consumption, particularly in self-refresh modes, as existing temperature sensors struggle to effectively recognize temperature signal variability.
Innovation Solution
A temperature sensor design that compares a constant reference voltage with a variable voltage, utilizing a gate voltage generation unit and a variable voltage output unit with offsetting resistances and threshold voltages of MOS transistors to generate a temperature signal that linearly changes with temperature, enabling precise temperature monitoring and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing temperature sensors are used to control operation conditions according to temperature variation, then temperature monitoring function is provided, but the temperature signal variability cannot be effectively recognized due to PVT variation
Solution Approach 1:
The patent changes the functional parameters of the temperature sensor by using a bandgap reference voltage generator that produces a reference voltage with a specific temperature coefficient. This reference voltage is compared against a bandgap voltage to generate a temperature signal that linearly varies with temperature, enabling effective recognition of temperature variability even under PVT (Process, Voltage, Temperature) variations.
Solution Approach 2:
The patent introduces a bandgap reference voltage generator as an intermediary component that mediates between the physical temperature and the digital temperature signal. This intermediary converts temperature variations into a standardized voltage signal that can be reliably processed by the control logic, improving both measurement precision and reliability under PVT variation.
2Loss of energy
If refresh period is not adjusted according to temperature, then operation is simple, but current consumption increases in self refresh mode
Solution Approach 1:
The patent implements a feedback mechanism where the temperature signal generated by the bandgap reference voltage generator is fed back to the control logic, which then adjusts the refresh period accordingly. This closed-loop feedback system automatically optimizes current consumption by adapting the refresh rate to the actual temperature conditions without requiring complex manual intervention.
Solution Approach 2:
The patent makes the refresh period dynamic rather than static by linking it to the temperature signal. The refresh period automatically changes based on temperature variations, allowing the system to operate efficiently across different temperature conditions. This dynamic adaptation reduces average current consumption while maintaining data integrity.
3Measurement precision
If a complex temperature sensor circuit is used to achieve high precision temperature measurement, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent achieves high-precision temperature measurement by making the bandgap reference voltage generator serve multiple functions: it provides both the reference voltage for comparison and the temperature signal generation. This multi-functional design eliminates the need for separate complex temperature sensing circuits, thereby maintaining measurement precision while reducing overall device complexity.
Solution Approach 2:
The patent merges the reference voltage generation function with the temperature sensing function into a single integrated circuit block. By combining these functions, the patent achieves precise temperature measurement without requiring additional complex circuitry, thus improving measurement precision while controlling device 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
This design allows for efficient temperature signal recognition and control, reducing current consumption by adjusting refresh periods based on temperature changes, thereby improving the performance and power efficiency of semiconductor memory devices.
Implementation Method 1
resistance changes of the bias resistor and the first source resistor based on temperature change are offset by each other, and slope change of the gate voltage based on the temperature change is determined according to a threshold voltage of the first MOS transistor
Implementation Method 2
resistance changes of the output resistor and the second source resistor based on temperature change are offset by each other, and slope change of the variable voltage based on the temperature change is determined according to a threshold voltage of the second MOS transistor
Implementation Method 3
compares a reference voltage having a constant level according to temperature change with a variable voltage having a variable level according to temperature change and generates a temperature signal
Data Source
AI summary
A temperature sensor includes: a gate voltage generation unit including a bias resistor, a first source resistor, and a first MOS transistor and configured to generate a gate voltage; and a variable voltage output unit including an output resistor, a second source resistor, and a second MOS transistor and configured to generate the variable voltage.