Word Line Driver Circuit for High-Voltage Reliability and Low Through-Current
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Solution Overview
Problem
The reliability of semiconductor devices with CMOS gate word line drivers is compromised due to dielectric breakdown in MOS transistors caused by high voltage application, leading to increased power consumption and reduced reliability.
Innovation Solution
A driving circuit with a first inverter driven by a first power supply voltage and a second inverter driven by a higher power supply voltage, along with a PMOS transistor and NMOS transistor configuration that controls current flow based on output signals, and a second PMOS transistor temporarily turned on to synchronize with the falling input signal, reducing the risk of dielectric breakdown and through-current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high voltage is applied to the word line driver to accurately read data from memory cells, then the reading accuracy is improved, but the MOS transistors suffer dielectric breakdown leading to reduced reliability
Solution Approach 1:
The word line driver is divided into multiple stages: a first stage driven by a first power supply voltage and a second stage driven by a second power supply voltage higher than the first. This segmentation allows different parts of the circuit to operate at different voltage levels, enabling high voltage application to the word line for accurate reading while protecting the MOS transistors in the first stage from dielectric breakdown by keeping them at a lower, safer voltage level.
2Reliability
If different power supply voltages are used for the first and second inverters to protect MOS transistors, then the reliability is improved, but the power consumption increases due to through-current
Solution Approach 1:
A second PMOS transistor is added that is temporarily turned on in synchronization with the falling edge of the first input signal. This preliminary action prepares the circuit for the voltage transition by pre-charging or pre-discharging relevant nodes, ensuring that when the first input signal falls, the transition between the two power supply voltage levels occurs smoothly and quickly. This reduces the duration of simultaneous transistor activation and minimizes through-current, thereby reducing power consumption while maintaining the reliability benefits of differential voltage operation.
Data Source
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AI summary
According to an embodiment, a word line driver includes: a first inverter that is driven by a first power supply voltage and inverts and outputs a decode signal; a second inverter that is driven by a second power supply voltage and inverts and outputs the decode signal; a first PMOS transistor that is controlled to be turned on or off on the basis of an output signal of the second inverter; a first NMOS transistor that is controlled to be turned on or off on the basis of an output signal of the first inverter; and a second PMOS transistor that is provided between a power supply voltage terminal to which the second power supply voltage is supplied and the gate of the first PMOS transistor and is temporarily turned on in synchronization with falling of the decode signal.