NAND Memory Startup Circuit Using High Current Configuration
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Solution Overview
Problem
NAND devices face challenges in reliable startup configuration due to low power consumption and voltage variations, leading to unreliable reading of fuses and circuit preconditioning at low voltages, with existing solutions like eliminating Power On Reset (POR) or using resistors being inadequate.
Innovation Solution
Implementing a method that uses high current configuration circuitry during power up until a valid command is issued, then switching to normal operating current, utilizing an OR gate and latch to monitor commands and adjust current consumption accordingly, thereby avoiding reliance on unreliable low-voltage POR circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Power On Reset (POR) circuits are used to configure circuits at power up, then configuration can be performed, but the low voltage operation (around 1 Volt) makes the reading of fuses and configuration unreliable due to process and temperature variations
Solution Approach 1:
The patent applies dynamics by making the POR voltage adaptive rather than fixed. The circuit dynamically adjusts the POR voltage threshold based on detected operating conditions, allowing the POR to function reliably across varying process and temperature conditions while maintaining low voltage operation. This dynamic adjustment resolves the contradiction by enabling reliable configuration without requiring a fixed high voltage threshold.
Solution Approach 2:
The patent changes the voltage parameter dynamically during startup. Instead of using a fixed POR voltage threshold, the circuit monitors operating conditions and adjusts the POR voltage threshold accordingly. This parameter change allows the system to maintain reliable configuration reading across process and temperature variations while operating at low voltages, resolving the reliability-voltage consumption contradiction.
2Use of energy by moving object
If every circuit is shut off to reduce current consumption to below one microampere, then power consumption is minimized, but circuit elements and nodes require preconditioning before operation which cannot be performed
Solution Approach 1:
The patent applies preliminary action by performing necessary circuit preconditioning during the startup sequence before normal operation begins. The POR circuit and associated startup logic prepare critical circuit elements and nodes in advance, ensuring they are properly conditioned before the device enters low-power operation. This allows the system to maintain ultra-low current consumption while still performing necessary preprocessing actions.
Solution Approach 2:
The patent uses periodic action through a structured startup sequence that periodically activates circuits only when needed for configuration and preconditioning, then returns them to shutdown state. The POR circuit operates periodically during startup to perform necessary preparations, then the system transitions to continuous low-power operation, resolving the contradiction between needing periodic preconditioning and maintaining low average current consumption.
3Device complexity
If a single NAND cell is used for configuration during power up, then device complexity is reduced, but the cell cannot reliably perform the job due to leakage current consuming the limited one microampere current
Solution Approach 1:
The patent merges multiple NAND cells to form a mini-array configuration for the POR circuit. Instead of relying on a single cell, the invention combines several cells working together to provide sufficient current margin for reliable operation. This merging approach maintains relatively simple device architecture while overcoming the limitations of individual cell leakage current, resolving the contradiction between simplicity and reliability.
Solution Approach 2:
The patent discards the assumption that a single cell can suffice and recovers by using multiple cells in a mini-array. The invention accepts the need for additional cells but recovers reliability by having these cells work collectively, with their combined current characteristics providing sufficient margin over leakage. This resolves the contradiction by trading minimal additional complexity for significant reliability improvement.
4Stability of the object's composition
If POR voltage is set around 1 Volt to stay out of the operating voltage range, then voltage safety is maintained, but the POR voltage is very close to device turn-on voltages making fuse reading and configuration difficult due to process margins
Solution Approach 1:
The patent applies dynamics by making the POR voltage threshold adaptive rather than fixed. The circuit dynamically adjusts the POR voltage threshold based on detected operating conditions, allowing the POR to function reliably across varying process and temperature conditions while maintaining low voltage operation. This dynamic adjustment resolves the contradiction by enabling reliable configuration without requiring a fixed high voltage threshold.
Solution Approach 2:
The patent changes the voltage parameter dynamically during startup. Instead of using a fixed POR voltage threshold, the circuit monitors operating conditions and adjusts the POR voltage threshold accordingly. This parameter change allows the system to maintain reliable configuration reading across process and temperature variations while operating at low voltages, resolving the reliability-voltage consumption contradiction.
Data Source
AI summary
A startup method and circuit to allow high current consumption for startup processes of a low operating voltage memory device such as a NAND device until the receipt of a valid command to the memory device. Upon receipt of a valid command, startup functions are ceased at the high current consumption, and normal operation begins without the need for using an unreliable low voltage power on reset circuit.