Embedded-Resistor Discharge Circuit for High-Voltage Snapback Control
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Solution Overview
Problem
Existing discharge circuits for high-voltage, high-capacitance nets in NAND flash memory face challenges in maintaining a safe operating area (SOA) and preventing snapback, while occupying a large area and having slow discharge rates.
Innovation Solution
The proposed discharge circuits utilize a single high-voltage transistor with an embedded area-neutral metal resistor, featuring adjustable negative-feedback source and drain resistances, and a stepped control signal to maintain SOA and enhance performance, reducing area consumption and discharge time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional stepdown discharge circuits are used, then discharge function is provided, but area consumption is large and discharge rate is slow
Solution Approach 1:
The discharge circuit merges the transistor and resistor into a single integrated unit cell structure. The metal resistor is formed within the same footprint as the transistor, eliminating the need for separate discrete resistor components and reducing overall area consumption while maintaining discharge functionality.
Solution Approach 2:
The discharge circuit achieves faster discharge rates by transitioning from a voltage-stepdown approach to a current-source approach, fundamentally changing the discharge mechanism dimension. This allows direct control of discharge current without intermediate voltage transformation steps, improving discharge speed.
2Reliability
If discharge circuit operates at high voltage, then discharge capability is provided, but snapback occurs and safe operating area is compromised
Solution Approach 1:
The discharge circuit incorporates negative feedback through the metal resistor connected to the source terminal. This feedback mechanism monitors the discharge current and automatically adjusts the transistor operation to prevent snapback, maintaining the circuit within the safe operating area during high-voltage discharge.
Solution Approach 2:
The circuit dynamically changes operating parameters during discharge by adjusting the effective resistance through the metal resistor. This parameter modulation allows the circuit to adapt to varying discharge conditions, preventing entry into the snapback region while maintaining discharge capability.
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
The solution effectively mitigates snapback and maintains SOA, achieving faster discharge rates and die-size reduction compared to traditional stepdown configurations.
Implementation Method 1
adjustable negative-feedback source and drain resistances
Implementation Method 2
embedded area-neutral metal resistor
Implementation Method 3
single high-voltage transistor with an embedded area-neutral metal resistor
Data Source
AI summary
A discharge circuit includes a transistor and a metal resistor connected to the transistor. The transistor includes a plurality of unit cells. The metal resistor includes a plurality of resistor portions corresponding to the plurality of unit cells. Each unit cell of the plurality of unit cells has a footprint and a corresponding resistor portion of the plurality of resistor portions is arranged within the footprint.