Sector-Based Program Voltage Regulation for NVM Arrays
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Solution Overview
Problem
Non-volatile memory (NVM) systems face challenges in maintaining consistent program voltages across NVM arrays due to IR voltage losses in distribution lines, leading to variations in the voltages applied to cells, especially in large arrays with varying distances and numbers of cells being programmed.
Innovation Solution
The implementation of sector-based regulation using sector return voltages as feedback to adjust program voltages, ensuring target voltage levels are maintained at the sector boundary, regardless of the sector or number of cells programmed, by incorporating a return distribution line configured as a high impedance load and utilizing a multiplexer for two-step feedback regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If program voltage is distributed through long distribution lines to NVM cells, then coverage area increases, but IR voltage losses cause voltage level variations
Solution Approach 1:
The NVM array is divided into multiple sectors, each with its own sector return voltage feedback path. This segmentation allows independent voltage regulation for each sector, compensating for IR drops in long distribution lines while maintaining overall array coverage.
Solution Approach 2:
A feedback mechanism is implemented using sector return voltages that are fed back to the voltage pump circuitry. The feedback signal adjusts the program voltage to compensate for IR voltage losses, ensuring consistent voltage levels across the entire NVM array regardless of distribution line length.
2Productivity
If more cells are programmed simultaneously, then productivity increases, but IR voltage losses increase causing greater voltage variations
Solution Approach 1:
The sector return voltage feedback dynamically adjusts the program voltage based on the actual voltage delivered to the cells. When more cells are programmed simultaneously, the feedback mechanism compensates for the increased IR losses, maintaining accurate voltage levels and enabling high productivity without sacrificing precision.
Solution Approach 2:
The system dynamically changes the program voltage parameter based on the number of cells being programmed and the resulting IR losses. The voltage pump circuitry adjusts the output voltage in response to feedback signals, optimizing voltage delivery for different programming scenarios.
3Device complexity
If voltage pump circuitry regulates program voltage at a central point, then voltage generation is simplified, but IR losses in distribution lines cause voltage drops at remote sectors
Solution Approach 1:
While maintaining a single central voltage pump circuitry, the system introduces feedback paths from each sector that monitor the actual voltage at the sector boundary. This feedback allows the central regulator to compensate for IR losses in distribution lines, achieving voltage consistency without adding multiple voltage pump circuits.
Solution Approach 2:
The solution adds a feedback dimension to the voltage regulation system. Instead of only controlling voltage at the source, the system now has a return path that carries voltage information from the load (sector boundary) back to the regulator, enabling remote sensing and compensation of IR drops.
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
This approach effectively compensates for IR voltage drops, ensuring consistent program voltages are applied to NVM cells, maintaining desired voltage levels and reducing variations, thereby improving programming accuracy and reliability across the NVM array.
Implementation Method 1
The regulation of the program voltage (VPRG) 108 is provided through a voltage feedback signal (VFB) 116 that is received by the voltage pump circuitry 102
Implementation Method 2
The voltage feedback signal (VFB) 116 is generated by a comparator 114 that compares the generated program voltage (VPRG) 108 to a reference voltage (VREF) 112
Implementation Method 3
A distribution line 208 feeds the HV output signal to control gate drivers. Each sector also has a source gate driver (SRCDrv) that applies a medium voltage (MV) output signal
Implementation Method 4
NVM systems include arrays of NVM cells that are programmed using program bias voltages applied to program nodes
Data Source
AI summary
Methods and systems are disclosed for sector-based regulation of program voltages for non-volatile memory (NVM) systems. The disclosed embodiments regulate program voltages for NVM cells based upon feedback signals generated from sector return voltages that are associated with program voltage drivers that are driving program voltages to NVM cells within selected sectors an NVM array. As such, drops in program voltage levels due to IR (current-resistance) voltage losses in program voltage distribution lines are effectively addressed. This sector-based regulation of the program voltage effectively maintains the desired program voltage at the cells being programmed regardless of the sector being accessed for programming and the number of cells being programmed. Sector return voltages can also be used along with local program voltages to provide two-step feedback regulation for the voltage generation circuitry. Test mode configurations can also be provided using test input and/or output pads.