Segmented Laser Driver Edge-Rate Control for Lower EMI
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Solution Overview
Problem
Existing optical driver circuits react quickly to enable signals, leading to sudden changes in current that generate large electromagnetic interference (EMI) and do not allow for customizable pulse shapes, which can be undesirable for digital signal processing in optical receivers.
Innovation Solution
The implementation of optical driver circuits with multiple drive cells and delay segments, where each drive cell receives a delayed enable control signal, allowing for controlled edge rates and customizable current changes through the use of transistors and programmable delay elements like shift registers or timers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the driver circuit reacts quickly to enable signals, then the response speed is improved, but electromagnetic interference increases
Solution Approach 1:
The driver circuit is divided into multiple drive cells (first drive cell, second drive cell, etc.) that are enabled sequentially through delay segments. This segmentation allows the total current change to be distributed over time across multiple cells, reducing the edge rate and EMI while maintaining fast overall response.
Solution Approach 2:
Delay segments are introduced to preliminarily control the timing of each drive cell's activation. By pre-calculating and implementing specific time delays for each cell, the circuit achieves controlled edge rates that reduce EMI while maintaining predictable response characteristics.
2Loss of time
If the driver circuit uses sudden current changes, then the response time is improved, but electromagnetic interference increases
Solution Approach 1:
The current change is segmented across multiple drive cells that activate in sequence. Each cell contributes a portion of the total current, and by controlling their sequential activation through delay segments, the overall response time remains short while EMI is reduced through controlled edge rates.
Solution Approach 2:
The circuit dynamically adjusts the activation timing of each drive cell using configurable delay segments. This dynamic control allows optimization of both response time and EMI by adjusting delay parameters to match specific application requirements.
3Device complexity
If the driver circuit uses fixed pulse shapes, then the circuit complexity is reduced, but adaptability decreases
Solution Approach 1:
The delay segments are configured with adjustable time delays that can be programmed or tuned to generate different pulse shapes. This dynamic configurability allows the same circuit topology to adapt to various digital signal processing requirements without increasing fundamental circuit complexity.
Solution Approach 2:
By changing the delay parameters of the delay segments, the circuit can generate different pulse shapes and edge rates. This parameter-based control provides versatility for different applications while maintaining a relatively simple fixed circuit architecture.
Data Source
AI summary
An optical driver circuit is described herein having a plurality of drive cells and delay segments between their control signals resulting in the control of the rising and falling edge rates for an optical device driven by the optical driver circuit.