Autonomous Output Impedance Adjustment in IC Output Drivers
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Solution Overview
Problem
Semiconductor integrated circuits, such as DRAM and pseudo-SRAM, face issues with impedance mismatch between the output driver and transmission lines, leading to signal reflection, and existing solutions require an external terminal for impedance adjustment, increasing the number of terminals and power consumption.
Innovation Solution
The integration of an output driver, replica driver, and replica resistor within the semiconductor integrated circuit package, with an impedance adjustment circuit that adjusts current driving capability based on output voltage, eliminating the need for an external terminal and reducing power consumption by controlling current flow through transistor switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external terminal is used for impedance adjustment, then impedance matching can be achieved, but the number of terminals increases
Solution Approach 1:
The patent merges the replica resistor from an external component into an internal circuit element within the semiconductor integrated circuit. The replica resistor is now formed inside the chip using the same semiconductor substrate, eliminating the need for external terminals while maintaining the impedance matching function through integration of the replica resistor with the output driver circuit.
Solution Approach 2:
The patent extracts the impedance adjustment function from requiring external hardware (external terminal and external replica resistor) and embeds it within the internal circuit structure. The replica resistor is extracted from the external package and repositioned as an internal element, allowing the impedance matching operation to be performed entirely within the chip without external terminal connections.
2Reliability
If an external terminal is used for impedance adjustment, then impedance matching can be achieved, but power consumption increases
Solution Approach 1:
The patent combines the replica resistor circuit with the internal power supply of the semiconductor chip, eliminating the need for separate external power sources. By integrating the replica resistor and its biasing circuitry within the chip, the power consumption is reduced as the impedance adjustment function shares the chip's internal power infrastructure rather than requiring additional external power delivery paths.
3Object-affected harmful factors
If impedance adjustment is performed autonomously, then signal reflection is prevented, but circuit complexity increases
Solution Approach 1:
The patent uses a replica driver that copies the output driver's circuit structure and characteristics, including the replica resistor. This replica circuit mirrors the output driver's impedance characteristics, allowing the impedance matching to be achieved through the copied structure without requiring complex external adjustment mechanisms. The copying approach simplifies the overall system by using a scaled-down version of the output driver for impedance sensing and adjustment.
Data Source
AI summary
A semiconductor integrated circuit includes an output driver, a replica driver, a replica resistor, and an impedance adjustment circuit. The output driver is configured to be capable of changing current driving capability. The replica driver is configured to be capable of changing current driving capability. The replica resistor is connected to an output of the replica driver. The impedance adjustment circuit is configured to adjust the current driving capability of the output driver and the replica driver, based on an output voltage of the replica driver. In addition, the output driver, the replica driver, the replica resistor, and the impedance adjustment circuit are mounted in an integrated circuit package.