Clamp Voltage Generator Circuit for Semiconductor Memory
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional clamp voltage generating circuits in semiconductor memory apparatuses face issues with uneven threshold voltages, leading to incorrect sensing of data stored in memory units, due to inconsistencies in the voltage conditions between the charge transfer transistor and the emulate transistor within the clamp voltage generating circuit.
Innovation Solution
A semiconductor memory apparatus with a clamp voltage generating circuit that includes a transistor with a drain coupled to a first potential, a source coupled to a node, and a gate coupled to the clamp voltage, along with a current setting element and a constant voltage output element. The current setting element sets a drain current using parallel-connected current setting transistors and current sources, and the constant voltage output element regulates the clamp voltage to ensure consistency with a reference voltage, duplicating the current of the bit line to match the condition of the charge transfer transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intrinsic transistors with low threshold value are used to generate clamp voltage, then the clamp voltage can reach low level required for data determination, but the threshold values become uneven leading to incorrect sensing
Solution Approach 1:
The patent introduces an emulate transistor that copies the electrical characteristics and operating conditions of the charge transfer transistor. By duplicating the transistor structure, threshold voltage, and voltage conditions, the circuit compensates for threshold variations without requiring perfectly uniform intrinsic transistors. The emulate transistor serves as a reference model that replicates the actual transistor's behavior under identical conditions.
Solution Approach 2:
The patent changes the parameter being controlled from direct threshold voltage matching to voltage condition matching. Instead of relying on uniform threshold voltages of intrinsic transistors, the system adjusts and matches the voltage conditions (Vgs, Vds) between the charge transfer transistor and emulate transistor. This parameter transformation allows the use of varied threshold transistors while achieving consistent operational characteristics through voltage regulation.
2Reliability
If voltage conditions between charge transfer transistor and emulate transistor are not aligned, then circuit operation becomes incorrect, but aligning them requires additional voltage regulation mechanisms
Solution Approach 1:
The patent implements a feedback mechanism where the gate voltage of the emulate transistor is regulated based on the voltage conditions of the charge transfer transistor. The constant voltage output element monitors the voltage differential and adjusts the emulate transistor's gate voltage accordingly, creating a closed-loop system that automatically maintains voltage condition alignment without complex external regulation circuits.
Solution Approach 2:
The constant voltage output element acts as an intermediary between the charge transfer transistor and the emulate transistor. It mediates the voltage conditions by regulating the gate voltage of the emulate transistor to match the charge transfer transistor's conditions, thereby enabling correct operation without direct complex coupling between the transistors themselves.
3Manufacturing precision
If conventional clamp voltage generating circuits are used, then the circuit structure remains simple, but threshold voltage unevenness causes wrong data sensing
Solution Approach 1:
The core of the invention is the emulate transistor that copies the charge transfer transistor's characteristics. This copying approach allows the circuit to achieve high manufacturing precision in data sensing by replicating the actual transistor's behavior, while adding only minimal circuit elements (emulate transistor and voltage regulation) rather than completely redesigning the clamp voltage generating circuit.
Solution Approach 2:
The emulate transistor serves multiple functions: it acts as a reference device for threshold voltage compensation, a model for voltage condition matching, and a basis for generating corrected clamp voltage. This multi-functionality allows a single additional transistor to address threshold unevenness, simplify voltage regulation requirements, and improve sensing accuracy simultaneously, thereby achieving high manufacturing precision without proportionally increasing device complexity.
Data Source
AI summary
The invention provides a clamp voltage generating circuit capable of generating a correct clamp voltage. The clamp voltage generating circuit includes an emulate transistor, having a drain coupled to a power source VDD, a source coupled to a node, and a gate coupled to the clamp voltage; a current setting circuit, connected between the node and ground, for setting a current flowing from the node to the ground; a regulator, inputting a feedback voltage from the node and a reference voltage, and outputting a voltage VCLMP. The current setting circuit duplicates a current of a bit line, so that the emulate transistor is similar to a charge transfer transistor.