Why Signal and Power Integrity (SI/PI) Are Crucial
As digital signal frequencies on PCBs continue to rise, bit rates on fast serial interfaces now exceed 20Gbps per lane (e.g., DP2.0, USB4). At this speed, high-speed digital interface design transitions into RF design. This is where signal integrity analysis and signal integrity simulation tools become essential.
Signal Integrity for Signal Quality
The primary goal of signal integrity (SI) work is to ensure a clean signal reaches the receiving circuit in electronics. The signal can suffer distortion from non-ideal sections on the transmission line or from coupled noise. Signal integrity efforts aim to minimize these effects through thoughtful electronics design.
Signal Quality for Reliable Operation
Reliable signaling within or between electronic boards ensures the absence of bit errors, reducing the need for data resending or error correction. This results in several key benefits:
Bad, small blurry eye
Good, clear open eye
Signal quality target
A common method to assess signal quality at the receiving circuit is using a signal eye diagram. If the signal eye is not sufficiently open, errors may occur at reception. A blurry signal eye necessitates heavy error correction and increased software self-awareness for data corruption.
Key design considerations for achieving optimal signal integrity include:
- Signal path lengths between differential pairs
- Printed circuit board layer stack-up structure to achieve proper line impedances
- Minimizing the number of vias on the signal path and optimizing via impedance
- Proper grouping of signal traces on the board
- Designing component and connector pad areas to match the needed impedances
- Appropriate placement, pads, and layout of possible signal components
Analyzing Signal Integrity
Signal integrity analysis estimates and evaluates the signal shape and quality at the receiving circuit. Methods such as signal eye diagram measurements ensure that signal levels and rise/fall times are adequate. However, measurement isn’t always feasible when traces are hidden under components or within inner layers. In such cases, signal integrity simulation tools are the only viable option.
A drawback of this after-layout approach is that results come after the design is complete. To address this, the work is divided into pre-layout and post-layout phases. In the pre-layout phase, critical signal path details are analyzed and design guidelines are created. The post-layout phase involves analyzing the completed design.
Our latest news & blogs related to EMC/EMI and SI/PI-simulations:
The question to consider for SI/PI:
1. Do you have a large PCB with a limited point of power? If yes, how do you know that there is a proper supply voltage to the chips?
Do you have a crowded PCB and limited space for traces?
2. How to make sure that the power lines are strong enough between the vias breaking power plane?
3. How to make sure that the signals are not disturbing each other?
4. Do you know what is the received signal quality on the chip (especially if the trace is not in a visible layer)?
5. Do you have fast and long signal interfaces, which need to be designed like transmission lines?
6. Do you have differential signals, where balance needs to be maintained?
7. Do you need to run certification analysis for memory lines (DDR4)?
We are happy to help you forward with these questions. Contact us to discuss with our expert on Power and Signal Integrity!
Signal Integrity (SI) Simulation – Check and Improve Your High-Speed PCB Performance
We utilize advanced 3D EM signal integrity simulation tools to optimize critical portions of high-speed lane routing, including vias, components, and connector areas. Simulations provide data on routing impedances and S-parameter models, revealing the transmission path’s frequency response. These models allow for the tuning of equalization where applicable. We also conduct lower frequency (< 5GHz) analyses to adjust driver strengths and terminations, which are often necessary for fast clock signals and memory interfaces (e.g., SC cards, DRAMs).
Power Integrity (PI)
Power integrity analysis assesses the power delivery network (PDN) performance for both AC and DC. DC analysis ensures adequate power delivery without significant voltage drops or high current densities, enhancing reliability. AC impedance analysis of the PDN verifies that it meets the specifications for high-performance ICs. This process ensures effective power delivery at higher frequencies, improving EMI levels in processor subsystems.
- S-parameter and TDR analysis of fast interfaces, supporting over 20Gbps/lane
- Signal waveform analysis (SI)
- AC and DC PDN analysis (PI)
By incorporating signal integrity simulation and power integrity analysis into your design process, you can ensure high performance and reliability in your high-speed digital designs.
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