Output Driver Feedback Network for Slew Rate and EMI Reduction
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Solution Overview
Problem
Conventional slew rate reduction designs for output drivers in semiconductor devices are not cost-effective and suffer from ineffective performance, occupying large die areas or showing insignificant tuning effects due to the use of capacitor arrays or RC control.
Innovation Solution
An output driver design incorporating a feedback network with pre-driver and driver circuits, and inverter-based feedback paths that perform latching operations to reduce slew rate without using capacitor arrays, thereby alleviating electromagnetic interference (EMI) while maintaining a compact chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional slew rate reduction design using capacitor arrays or RC control is implemented, then slew rate can be reduced, but die area increases and manufacturing cost increases
Solution Approach 1:
The patent implements a feedback network that monitors the output signal and feeds it back to the pre-driver stage. This feedback mechanism dynamically controls the pre-driver output based on the actual driver output, enabling slew rate reduction without requiring large capacitor arrays or RC circuits. The feedback loop adjusts the pre-driving signal to achieve controlled voltage transitions, resolving the contradiction between slew rate control and compact area.
2Speed
If conventional slew rate reduction design using capacitor arrays or RC control is implemented, then slew rate can be reduced, but manufacturing cost increases
Solution Approach 1:
The feedback network uses standard logic gates (AND, OR, NOT) and flip-flops that are conventional and cost-effective semiconductor components. By replacing expensive capacitor arrays and RC control circuits with these standard logic elements in a feedback configuration, the design achieves slew rate reduction at lower manufacturing cost while maintaining ease of fabrication.
3Speed
If conventional slew rate reduction design is implemented, then slew rate can be reduced, but performance is ineffective
Solution Approach 1:
The feedback network continuously monitors the driver output and adjusts the pre-driver signal in real-time, ensuring effective and reliable slew rate control. The latching mechanism using flip-flops ensures stable operation and prevents signal instability. This active feedback control provides superior performance effectiveness compared to passive RC or capacitor-based approaches.
Solution Approach 2:
The feedback network performs preliminary action by adjusting the pre-driver output signal before it reaches the driver stage. The latching operation prepares the signal in advance, controlling the voltage transition timing proactively. This preliminary control ensures effective slew rate management and improves overall system reliability.
Data Source
AI summary
An output driver includes a first pre-driver circuit, a first driver circuit, a second pre-driver circuit, a second driver circuit, and a feedback network. The first pre-driver circuit pre-drives a first data input signal to generate a first pre-driving output signal. The first driver circuit drives the first pre-driving output signal to generate a first data output signal. The second pre-driver circuit pre-drives a second data input signal to generate a second pre-driving output signal, wherein the first data input signal and the second data input signal are a differential input of the output driver. The second driver circuit drives the second pre-driving output signal to generate a second data output signal. The feedback network performs a latching operation upon the first pre-driving output signal and the second pre-driving output signal according to the first data output signal and the second data output signal.