Memory Device Calibration Without ZQ Pin
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Solution Overview
Problem
Semiconductor devices without a ZQ pin face challenges in impedance matching, leading to increased external noise, signal distortion, and issues like setup/hold failures due to decreased signal swing width, making high-speed data transmission difficult.
Innovation Solution
A calibration circuit that trims reference resistors based on external resistors to generate pull-up and pull-down calibration codes, controlling the termination of data input/output pads for accurate impedance matching without relying on a ZQ pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a ZQ pin is used for impedance matching calibration, then impedance matching accuracy is improved, but device complexity increases due to additional pins and calibration circuits
Solution Approach 1:
The patent extracts the ZQ pin function from the device by performing impedance matching calibration through existing internal pads (DQ pads) rather than requiring a separate external ZQ pin. The calibration circuit uses internal resistance elements and existing pad structures to accomplish the calibration function that traditionally required a dedicated ZQ pin, thereby reducing device complexity while maintaining calibration accuracy
Solution Approach 2:
The patent makes the existing DQ pads serve multiple functions: they are used for both normal data input/output operations and for impedance matching calibration operations. By configuring the calibration circuit to utilize the same physical pads for dual purposes, the invention eliminates the need for separate calibration pins while maintaining the ability to perform accurate impedance matching
2Speed
If signal swing width is decreased to minimize transmission time, then transmission speed is improved, but signal quality deteriorates due to increased external noise and distortion
Solution Approach 1:
The patent implements a feedback mechanism where the calibration circuit measures the actual impedance characteristics through the DQ pads and automatically adjusts the termination resistance values accordingly. This closed-loop feedback system ensures that even with decreased signal swing widths for high-speed operation, the impedance matching remains optimal, thereby maintaining signal quality despite faster transmission rates
Solution Approach 2:
The patent dynamically adjusts termination resistance parameters based on calibration results. The calibration circuit determines optimal resistance values and configures the termination circuits accordingly, allowing the system to adapt resistance parameters to maintain signal integrity at various transmission speeds. This parameter adjustment capability enables high-speed operation while compensating for the reduced signal swing width
Data Source
AI summary
Provided is a memory device configured to perform a calibration operation without having a ZQ pin. The memory device includes a calibration circuit configured to generate a pull-up calibration code and a pull-down calibration code which termination of a data input/output pad for impedance matching in the data input/output pad is controlled. The calibration circuit performs a first calibration operation for trimming first and second reference resistors based on an external resistor to be connected to a pad, and a second calibration operation for generating the pull-up calibration code and the pull-down calibration code based on the trimmed second reference resistor.