Memory RTT Trimming with Separate ZQ Calibration Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing memory devices face challenges in trimming termination resistance (RTT) due to fluctuations caused by process, voltage, and temperature (PVT) variations, which affect signal reflection and noise on transmission lines, particularly in different external pins.
Innovation Solution
The system generates separate ZQ calibration signals for different circuit areas within the memory device, such as DQ and CA pads, to adjust pull-up and pull-down resistances of driver units to predefined values, ensuring accurate RTT trimming across varying PVT conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ZQ calibration signal is used for all external pins, then the device complexity is reduced, but the RTT trimming precision for different external pins deteriorates due to PVT variations
Solution Approach 1:
The patent divides the calibration system into separate ZQ calibration signals for different external pins (e.g., ZQ0 for DQ pins, ZQ1 for CA pins). Each pin group has its own calibration signal that can be independently adjusted to compensate for PVT variations specific to that group, thereby improving RTT trimming precision without significantly increasing overall device complexity
Solution Approach 2:
The patent applies different calibration values and signaling characteristics to different external pin groups based on their specific PVT characteristics. Each pin group receives customized calibration parameters (e.g., different ZQ calibration codes) that are locally optimized for its operating conditions, rather than using a uniform calibration approach for all pins
2Manufacturing precision
If separate ZQ calibration signals are generated for different circuit areas, then the RTT trimming precision is improved, but the device complexity increases
Solution Approach 1:
The patent implements a universal ZQ calibration mechanism that can serve multiple external pin groups through selective activation and configuration. The same basic calibration infrastructure (ZQ calibration circuitry, pull-up/pull-down resistors) is reused across different pin groups by switching between different calibration signals and configurations, reducing the need for completely separate calibration systems for each pin group
3Reliability
If driver unit resistances are adjusted to compensate for PVT variations, then the signal integrity is improved, but the control complexity increases
Solution Approach 1:
The patent employs feedback mechanisms where the calibration system monitors signal quality and PVT conditions, then automatically adjusts driver unit resistances through ZQ calibration signals. This closed-loop approach maintains signal integrity by continuously compensating for PVT variations without requiring manual intervention or complex control logic from the user
Solution Approach 2:
The calibration system automatically performs resistance adjustment of driver units based on detected PVT conditions and signal characteristics. The system self-regulates the pull-up and pull-down resistor values through internal calibration algorithms, eliminating the need for external control or manual tuning of driver unit resistances
Data Source
AI summary
Systems and methods are provided for trimming RTTs in a memory device. The effective termination resistance (RTT) of the ODT may be adjusted by adjusting one or more driver units having predefined values (e.g., 240 Ω. Because PVT characteristics may impact the driver unit values, resistances of the driver units may be fluctuated away from the predefined values (e.g., 240 Ω. ZQ calibration signals may be used to calibrate the resistances of the driver units to the predefined values (e.g., 240 Ω to trim the RTTs. Separate ZQ calibration signals may be generated for different circuits (e.g., a circuit associated with DQ pad, a circuit associated with CA pad). In addition, two ZQ calibration signals may be generated simultaneously by a ZQ circuit during the same time period.