LVDS Driver Switch Sequencing to Prevent Current Interruption
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Solution Overview
Problem
Conventional LVDS differential output drivers experience performance degradation and noise introduction due to switches not operating identically and not opening/closing at precise times, leading to current interruption and transistors entering the triode region.
Innovation Solution
A sequencing circuit that deliberately sequences the switching of transistors in LVDS differential output drivers to ensure current is never interrupted, keeping current source transistors in saturation, by switching one set of transistors on before switching off another, reducing intrinsic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional switches are used in LVDS differential output drivers, then the circuit can be simple, but the switches do not open and close at precisely the desired time causing noise and performance degradation
Solution Approach 1:
The sequencing circuit performs preliminary action by switching on the first set of transistors before switching off the second set of transistors. This advance preparation ensures that current paths are established before previous paths are terminated, eliminating timing uncertainties and preventing noise generation at the output.
2Ease of operation
If switches are operated without sequencing, then the operation is straightforward, but current interruption occurs and transistors enter the triode region causing noise
Solution Approach 1:
The sequencing circuit ensures continuity of useful action by maintaining continuous current flow through the load. The first set of transistors is switched on before the second set is switched off, creating an overlap period where both sets conduct simultaneously. This eliminates current interruption and prevents transistors from entering the triode region, thereby eliminating the primary source of intrinsic noise.
3Speed
If transistors are switched off immediately after switching on, then the switching speed is fast, but noise is introduced due to simultaneous switching
Solution Approach 1:
The sequencing circuit applies preliminary action by advancing the turn-on signal for the first set of transistors before the turn-off signal is applied to the second set. This temporal sequencing ensures that current paths are established in advance, allowing fast switching operation while preventing the simultaneous switching that generates noise.
Data Source
AI summary
Systems and methods are disclosed herein to provide improved I/O techniques. For example, in accordance with an embodiment of the present invention, an integrated circuit includes a driver that receives data signals and provides an output signal based on the data signals, with the driver having a plurality of transistors with a first set of the plurality of transistors adapted to provide a first logical value as the output signal and a second set of the plurality of transistors adapted to provide a second logical value as the output signal based on the data signals. A sequencing circuit provides the data signals to the driver such that the first set of the plurality of transistors is switched on before the second set of the plurality of transistors is switched off, and the second set of the plurality of transistors is switched on before the first set of the plurality of transistors is switched off.