Output Driver Slew-Rate Switching for Low-Voltage Signal Integrity
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Solution Overview
Problem
Reducing power voltage in semiconductor devices leads to increased influence of harmonic components and crosstalk, disrupting signal propagation and making it difficult to achieve good signal quality at high data transmission rates.
Innovation Solution
A semiconductor device with a characteristic switching circuit that adjusts the slew rate and output impedance of the output driver, maintaining rising and falling times of the output signal regardless of power voltage changes, thereby matching impedance and amplitude ratios to ensure correct signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power voltage is reduced to lower power consumption, then energy efficiency is improved, but signal quality deteriorates due to increased harmonic components and crosstalk
Solution Approach 1:
The patent changes the slew rate parameter of the output driver based on power voltage levels. When power voltage is reduced, the slew rate is adjusted to maintain constant rising and falling times, which prevents increase in harmonic components and crosstalk, thereby maintaining signal quality while enabling lower power operation
Solution Approach 2:
The patent dynamically adjusts the slew rate of the output driver according to the power voltage level. The slew rate control circuit modifies the slew rate in real-time based on detected power voltage conditions, enabling the system to adapt to different power states while maintaining consistent signal characteristics
2Productivity
If slew rate is maintained when reducing power voltage, then output driver performance is preserved, but signal propagation is disturbed due to increased harmonic components
Solution Approach 1:
The patent changes the slew rate parameter based on power voltage levels. When power voltage is reduced, the slew rate is adjusted to maintain constant rising and falling times, which prevents increase in harmonic components and crosstalk, thereby maintaining signal quality while enabling lower power operation
3Use of energy by moving object
If power voltage is reduced, then power consumption is lowered, but impedance matching becomes difficult affecting signal transmission
Solution Approach 1:
The calibration circuit adjusts the output impedance of the output driver based on the power voltage level. When power voltage is reduced, the output impedance is modified to maintain proper impedance matching with the transmission line, ensuring correct signal transmission despite the lower power state
Data Source
AI summary
The semiconductor device includes an output driver and a characteristic switching circuit that switches characteristics of the output driver. The characteristic switching circuit mutually matches a rising time and a falling time of an output signal output from the output driver, when a power voltage supplied to a power line is a first voltage, with a rising time and a falling time of the output signal output from the output driver, when the power voltage supplied to the power line is a second voltage. As a result, an increase in an influence of a harmonic component or a crosstalk when the power voltage is reduced does not occur. Moreover, because a receiving condition on a receiver side does not change even when the power voltage is reduced, signal transmission and reception can be performed correctly irrespective of the power voltage.