ZQ Resistor Calibration Circuit for Separate Ron and Rtt Codes
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Solution Overview
Problem
NAND Flash memory devices face challenges in accurately calibrating on-chip pull-up and pull-down resistors due to intrinsic mismatches between Ron and Rtt values, leading to compromised resistor code choices that are less optimal for one type of resistor when suitable for the other, resulting in varying performance across different batches and memory circuits.
Innovation Solution
A ZQ resistor calibration circuit and method that generates separate resistor codes for Ron and Rtt categories using a logic code generator and post-adjustment function circuits, allowing for tailored calibration values to minimize circuitry and enhance accuracy, while maintaining backward compatibility with older DDR3 standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single resistor code is used for both Ron and Rtt calibration, then device complexity is reduced, but manufacturing precision deteriorates due to intrinsic mismatches between Ron and Rtt values
Solution Approach 1:
The patent divides the calibration process into two separate segments: one for Ron calibration and another for Rtt calibration. Each segment has its own dedicated logic code generator and post-adjustment function circuit, allowing independent optimization of resistor codes for each type without compromise from intrinsic mismatches.
Solution Approach 2:
The patent applies local quality by providing tailored calibration values specifically optimized for each resistor type (Ron and Rtt). The post-adjustment function circuits generate different resistor codes based on the specific requirements of each resistor category, ensuring optimal performance for each local calibration need rather than using a uniform approach.
2Manufacturing precision
If separate resistor codes are generated for Ron and Rtt categories, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the functionality of multiple calibration operations into a unified calibration circuit architecture. Both Ron and Rtt calibration functions share common components including the calibration comparator, reference resistor, and control logic, while only duplicating the necessary post-adjustment function circuits to generate different resistor codes.
Solution Approach 2:
The calibration circuit is designed with universal components that can serve multiple functions. The same calibration comparator and reference resistor structure is used for both Ron and Rtt calibration, and the logic code generator can produce codes for both resistor types by activating different post-adjustment function circuits, reducing overall circuit complexity.
3Manufacturing precision
If calibration values are optimized for one resistor type, then manufacturing precision for that type is improved, but reliability deteriorates due to compromised performance in the other resistor type
Solution Approach 1:
The calibration system is segmented into independent calibration paths for Ron and Rtt, each with its own optimized resistor code generation. This segmentation allows each resistor type to receive tailored calibration values optimized for its specific characteristics, eliminating the compromise that would occur with a single shared calibration code.
Solution Approach 2:
The patent changes the calibration parameters by generating different resistor codes for Ron and Rtt categories. The post-adjustment function circuits modify the base resistor code to create type-specific calibration values, ensuring that each resistor type operates at its optimal performance point rather than using a compromised universal value.
Data Source
AI summary
In certain aspects, a circuit for ZQ resistor calibration can include a first input configured to receive a first default configuration. The circuit can also include a second input configured to receive a first calibration value based on a first comparison. The circuit can further include a first output configured to provide a first resistor code for a first resistor category. The circuit can additionally include a second output configured to provide a second resistor code for a second resistor category different from the first resistor category. The circuit can also include a first logic circuit configured to receive a signal from the first input and a signal from the second input, and provide a signal to the first output. The signal to the first output can include the first resistor code. The first resistor code can be different from the second resistor code.