Block Decoder Area Reduction via High-Voltage Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor memory apparatuses face challenges in reducing the size of block decoders due to large high-voltage switches, which occupy significant area and can malfunction due to gate oxide layer failures when high voltages are applied.
Innovation Solution
A block decoder design that includes a first selection unit for generating a block select signal and a second selection unit for controlling the potential level of the block select signal, using general high-voltage NMOS transistors instead of depletion-type transistors, and amplifying block address signals to generate high-voltage block address signals for efficient high-voltage switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If depletion-type transistors are used for high-voltage switching in block decoders, then reliable high-voltage control is achieved, but the decoder area increases significantly
Solution Approach 1:
The patent changes the transistor type from depletion-mode to enhancement-mode, and modifies the voltage levels of control signals. By applying a high-voltage block select signal (e.g., 20V) to the gate of the enhancement-mode transistor, the transistor is turned on to conduct high voltage, while a low voltage (0V or negative voltage) turns it off. This parameter change allows enhancement-mode transistors to replace depletion-mode transistors, reducing area while maintaining reliability.
Solution Approach 2:
The patent introduces dynamic control of the transistor state through time-varying control signals. The block select signal dynamically transitions between high voltage (on state) and low voltage (off state) based on decoding requirements. This dynamic operation allows the use of enhancement-mode transistors which require active voltage control, unlike static depletion-mode transistors that are naturally on and require negative voltage to turn off.
2Reliability
If high voltage is applied to the block select signal, then proper high-voltage control is achieved, but gate oxide layer failure occurs
Solution Approach 1:
The patent segments the voltage control function into two separate signals: a high-voltage block select signal for turning on the transistor, and a low-voltage block address signal for selecting specific blocks. The high voltage is applied only to the gate during the on-state, while the off-state uses low voltage. This segmentation of voltage levels throughout the operation cycle prevents gate oxide layer failure while maintaining high-voltage control capability.
Solution Approach 2:
The patent applies preliminary action by pre-charging or pre-positioning the gate voltage to appropriate levels before high-voltage switching occurs. The block decoder generates the high-voltage block select signal in advance to ensure the transistor is properly biased before high-voltage operation, preventing sudden voltage transients that could damage the gate oxide layer.
3Area of stationary object
If block decoder size is reduced, then integration density improves, but high-voltage switch area must be minimized
Solution Approach 1:
The patent changes the controlling parameter from gate-source voltage (in depletion-mode) to gate voltage relative to source (in enhancement-mode). By using enhancement-mode transistors controlled by high-voltage block select signals, the transistor on-resistance is reduced and switching performance is improved while occupying less area compared to depletion-mode transistors which require larger dimensions for equivalent performance.
Data Source
AI summary
A block decoder including a first selection unit configured to receive a block address signal and output a block select signal to any one of a plurality of blocks, and a second selection unit configured to receive a high voltage and control a potential level of the block select signal according to the block address signal.