AC-Coupled ZQ Calibration Circuit for High-Capacitance Memory Stacks
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Solution Overview
Problem
Semiconductor memory devices face challenges in reducing ZQ calibration execution time due to increased loading capacitance values in multi-die packages, leading to improper calibration and compromised signal integrity.
Innovation Solution
Incorporation of a ZQ calibration circuit with a charge injection circuit using an AC coupling capacitor to enhance the voltage change rate of the ZQ node, thereby improving calibration efficiency and signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the loading capacitance value is increased in multi-die packages, then the data capacity and operating speed are improved, but the ZQ calibration execution time is extended and calibration reliability deteriorates
Solution Approach 1:
The charge injection circuit performs preliminary action by injecting charge onto the ZQ node before the ZQ calibration operation begins. This pre-charging action accelerates the voltage transition at the ZQ node during calibration, allowing the calibration to complete faster despite the increased loading capacitance from multi-die packages.
Solution Approach 2:
The invention changes the electrical parameters at the ZQ node by injecting a specific amount of charge to modify the voltage transition characteristics. This parameter change (voltage change rate) is controlled through the charge injection circuit, which adjusts the charging behavior to optimize calibration speed while maintaining accuracy.
2Speed
If the swing width of signals is reduced to minimize transmission time, then the transmission speed is improved, but the influence of external noise and signal reflection increases
Solution Approach 1:
The ZQ calibration circuit uses feedback by comparing the voltage at the ZQ node with a reference voltage during calibration. This feedback mechanism allows the system to adjust the driver resistance dynamically to achieve impedance matching, thereby reducing signal reflection and improving signal integrity even with reduced swing widths.
Solution Approach 2:
The invention introduces dynamic adjustment capability through the charge injection circuit, which actively modifies the voltage at the ZQ node during calibration. This dynamic control enables real-time optimization of impedance matching, allowing the system to maintain signal integrity while operating with reduced swing widths for faster transmission.
3Device complexity
If the ZQ calibration circuit operates without charge injection, then the circuit complexity is reduced, but the calibration execution time increases and calibration reliability deteriorates
Solution Approach 1:
The charge injection circuit acts as an intermediary element that facilitates faster voltage transitions at the ZQ node during calibration. By introducing this intermediate charge injection mechanism, the system achieves faster calibration without requiring major structural changes to the overall circuit architecture, thus balancing complexity and performance.
4Quantity of substance
If multiple memories are included in a multi-die package, then the data capacity is increased, but the loading capacitance value increases causing improper ZQ calibration
Solution Approach 1:
The charge injection circuit performs preliminary charging of the ZQ node to compensate for the increased loading capacitance from multiple memories. This pre-action ensures that when calibration begins, the voltage transition occurs at an appropriate rate, maintaining calibration accuracy despite the higher total capacitance in multi-die packages.
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 proposed solution reduces ZQ calibration execution time and enhances signal integrity in multi-die packages, resulting in improved memory device performance.
Implementation Method 1
a charge injection circuit including a buffer and an alternating current (AC) coupling capacitor
Data Source
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AI summary
Provided is a memory device including a plurality of memories and an impedance adjustment (ZQ) resistor, wherein a memory from among the plurality of memories includes a ZQ pin connected to the ZQ resistor, and a ZQ calibration circuit configured to perform a ZQ calibration operation, wherein the ZQ calibration circuit includes a driver, and a charge injection circuit, wherein the charge injection circuit includes a buffer and an AC coupling capacitor, is connected to the ZQ pin, and receives a charge injection signal. In response to a voltage level of a ZQ node being higher than a level of a reference voltage, the charge injection signal transitions from logic high to logic low, and, in response to the voltage level of the ZQ node being lower than the level of the reference voltage, the charge injection signal transitions from logic low to logic high.