Output Buffer Slew Rate Control Under Power Supply Noise
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Solution Overview
Problem
Existing semiconductor devices face challenges in precisely controlling the slew rate of output buffer circuits due to power supply noise, as the source power for the slew rate control signal generation circuit differs from that of the output buffer circuit, leading to difficulties in maintaining accurate control.
Innovation Solution
The semiconductor device incorporates a buffer circuit that converts pre-slew rate control signals into slew rate control signals, operating on independently supplied source voltages, allowing precise control of the slew rate by regulating the number of transistors in the slew rate regulator circuit based on the slew rate control signal, thereby isolating the output buffer circuit from noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the source power for the slew rate control signal generating circuit is made independent from the source power for the output buffer circuit, then power supply noise propagation is prevented, but slew rate control precision deteriorates due to noise in the source power supplied to the output buffer circuit
Solution Approach 1:
A buffer circuit is introduced as an intermediary between the control circuit and the output buffer circuit. This buffer circuit receives the slew rate control signal from the control circuit (which operates on noise-free third and fourth source lines) and generates a cleaned slew rate control signal that operates on the first and second source lines. The buffer circuit acts as a mediator that transfers the control function while isolating the control circuit from power supply noise in the output buffer's power lines, thus maintaining both noise isolation and control precision.
2Object-generated harmful factors
If the source power for the output buffer circuit is supplied independently, then noise propagation to other circuits is reduced, but precise slew rate control becomes difficult due to noise in the independent source power
Solution Approach 1:
The buffer circuit serves as an intermediary that receives the control signal from the noise-free control circuit and generates a corresponding signal that operates on the noisy first and second source lines. This intermediary approach allows the output buffer to have independent power supply (reducing noise propagation to other circuits) while the buffer circuit ensures the control signal remains precise by being generated from the noise-free third and fourth source lines.
Data Source
AI summary
Disclosed herein is a device that includes: a first circuit configured to operate on a first power voltage to produce a first set of slew rate control signals; a second circuit configured to operate on a second power voltage to produce a second set of slew rate control signals in response to the first set of slew rate control signals; and a third circuit configured to operate on the second power voltage to produce a signal at a rate that is controllable in response to the second set of slew rate control signals.