Temperature-Compensated Internal Voltage Circuit for Stable DRAM Bias
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Solution Overview
Problem
The internal voltage generating circuit in semiconductor memory devices, such as DRAM, experiences variations in driving force due to temperature changes, affecting the stability of cell plate voltage and bit line precharge voltage, which is critical for data retention and signal detection.
Innovation Solution
An internal voltage generating circuit is designed with a voltage divider, pull-down and pull-up signal generators, and a driving unit that adjust their driving forces based on temperature signals, using a combination of PMOS and NMOS transistors to maintain a predetermined driving force regardless of temperature variations, by compensating with increased or decreased driving forces and adjusting the number of drivers accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the internal voltage generating circuit uses PMOS and NMOS transistors to generate voltage, then the circuit can provide the necessary driving force for voltage generation, but the threshold voltage and current driving force of the transistors change with temperature, causing the generated voltage level to fluctuate
Solution Approach 1:
The patent changes the driving force parameter of the voltage generating circuit based on temperature conditions. A temperature sensing circuit detects temperature and generates a temperature signal that controls the number of parallel transistor connections in the voltage generating circuit. At lower temperatures where transistor driving force is stronger, fewer transistors are activated to reduce excessive driving force. At higher temperatures where driving force weakens, more transistors are activated to compensate and maintain stable voltage output.
2Quantity of substance
If the cell size is reduced to achieve high density, then the memory capacity increases, but the operating current is gradually reduced, making stable data retention more difficult
Solution Approach 1:
The patent implements a dynamic adjustment mechanism where the voltage generating circuit adapts its driving force based on real-time temperature sensing. The temperature signal dynamically controls the configuration of transistor connections, switching between different numbers of parallel transistors to optimize the driving force at different temperatures, thereby ensuring stable voltage supply for data retention across varying operating conditions.
3Adaptability or versatility
If the threshold voltage of transistors changes with temperature, then the transistor characteristics vary, but this causes the internal voltage generation level to change, affecting bit line precharge voltage and cell plate voltage stability
Solution Approach 1:
The patent employs a feedback mechanism where a temperature sensing circuit continuously monitors the temperature and generates a temperature signal that feeds back to the voltage generating circuit. This feedback loop allows the circuit to automatically adjust its driving force in response to temperature changes, compensating for transistor threshold voltage variations and maintaining stable output voltage levels for bit line precharge and cell plate operations.
Data Source
AI summary
Disclosed is an internal voltage generating circuit. The internal voltage generating circuit comprises a voltage divider for generating a level signal by voltage-dividing first internal voltage, a pull-down signal generator for generating a pull-down signal, which has a level adjusted according to a temperature, in response to the level signal, a pull-up signal generator for generating a pull-up signal, which has a level adjusted according to the temperature, in response to the level signal, and a driving unit for driving second internal voltage in response to the pull-down signal and the pull-up signal. Driving force of the driving unit for driving the second internal voltage is changed according to the temperature.