Output Buffer Circuit With Selective Termination and ESD Protection
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Solution Overview
Problem
Conventional on-chip termination resistors in semiconductor devices increase device size and require complex calibration, failing to efficiently manage signal reflections and electrostatic discharge (ESD) protection.
Innovation Solution
An output buffer circuit with a control unit and output driver that selectively performs driver, termination, and ESD protection operations, utilizing a switching unit and unit circuits with adjustable impedance to match transmission channel impedance, and an external calibration unit to adjust impedance based on external resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If on-chip termination resistors are implemented, then signal reflection is reduced, but device size increases
Solution Approach 1:
The output driver is designed to perform multiple functions: data output, center termination, pull-up termination, pull-down termination, and ESD protection. By integrating these functions into a single circuit block that can be selectively activated, the patent eliminates the need for separate termination resistors, thereby reducing device area while maintaining signal reflection reduction capability.
2Reliability
If on-chip termination resistors are implemented, then signal reflection is reduced, but device complexity increases
Solution Approach 1:
The same output driver circuit that performs data output is also used for termination functions. The calibration unit adjusts the impedance of this multi-functional circuit to match the transmission channel impedance, eliminating the need for separate calibration circuits for dedicated termination resistors.
Solution Approach 2:
The output driver performs self-calibration through the calibration unit, which automatically adjusts its impedance characteristics to match the transmission channel. This self-service approach eliminates the need for external calibration circuits and procedures.
3Area of stationary object
If multiple functions are integrated into output driver, then device size is reduced, but control complexity increases
Solution Approach 1:
The output driver uses switching signals to dynamically reconfigure its impedance characteristics and functional mode. The control unit generates switching signals that selectively activate different operational modes (data output, various termination types, ESD protection) based on real-time requirements, allowing the circuit to adapt its behavior without physical reconfiguration.
Data Source
AI summary
An output buffer circuit includes a control unit and an output driver. The control unit generates a control signal in response to a mode signal applied from an internal circuit. The output driver selectively performs a driver operation, a termination operation or an electrostatic discharge (ESD) protection operation in response to the control signal.