Compact PFET Pre-Driver for High-Voltage Wordline Conversion
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Solution Overview
Problem
Multi-stage wordline driver circuits in memory structures face undesirable trade-offs between area, power, and performance due to the use of both N-channel and P-channel field effect transistors, which require significant area and result in process, voltage, and temperature variations, with some devices operating outside their safe operating area.
Innovation Solution
A compact high voltage pre-driver is designed using four P-channel field effect transistors, all with identical voltage ratings, connected in series and cross-coupled to convert a low voltage input signal to a high voltage output signal, avoiding bulk spacing requirements and operating within safe operating area limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-stage wordline driver circuits use both N-channel and P-channel field effect transistors to convert low voltage to high voltage, then voltage conversion function is achieved, but area consumption increases and devices may operate outside safe operating area
Solution Approach 1:
The patent employs four P-channel field effect transistors with identical voltage ratings and characteristics, eliminating the need for mixed N-channel and P-channel devices. This homogeneous configuration ensures all transistors operate within their safe operating area while reducing area requirements compared to traditional mixed-device approaches.
Solution Approach 2:
The pre-driver circuit is segmented into four identical P-channel transistors connected in series, each handling a portion of the voltage conversion task. This segmentation allows the high voltage conversion function to be achieved while keeping individual device stress within safe limits, avoiding the need for larger high-voltage rated devices.
2Reliability
If multi-stage wordline driver circuits use both N-channel and P-channel field effect transistors, then voltage conversion is achieved, but process, voltage, and temperature variations increase
Solution Approach 1:
By using four identical P-channel field effect transistors instead of mixed N-channel and P-channel devices, the circuit exhibits improved process, voltage, and temperature stability. All transistors respond uniformly to PVT variations, eliminating mismatch issues that arise from combining different device types with different characteristics.
3Power
If conventional pre-drivers are designed to handle high voltage operation, then high voltage output is achieved, but area increases due to bulk spacing requirements
Solution Approach 1:
The patent achieves high voltage operation by changing the configuration parameters of standard-voltage-rated P-channel transistors. By connecting four identical transistors in series and appropriately biasing their gates, the circuit achieves high voltage output capability without requiring transistors with large bulk spacing, thus maintaining compact area.
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 reduces area consumption, improves performance with reduced delay and current, and minimizes process, voltage, and temperature variations, while maintaining high voltage operation without violating voltage ratings.
Implementation Method 1
a first P-channel field effect transistor (PFET) with a first gate connected to the first input node, a second PFET with a second gate connected to the second input node
Data Source
AI summary
A pre-driver includes first, second, third, and fourth P-channel field effect transistors (PFETs) with voltage ratings equal to a low first voltage (V1). Between power rails at V1 and at a higher second voltage (V2), the first and third PFETs are series-connected and the second and fourth PFETs are also series-connected. The third and fourth PFETs are cross-coupled. The first and second PFETs have gates that receive a pre-driver input signal (Pin) that switches between V2 and ground and an inverted pre-driver input signal (Pinb), respectively. At an output node between the first and third PFETs, the pre-driver outputs a driver input signal (Din) that switches between V2 and V1. A circuit includes this pre-driver (e.g., connected between a voltage level shifter and a driver or connected between a voltage level shifter and a buffer).