What test equipment is useful for analysis of PI and SI? - Page 1
Forum section: electronics / beginners

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: July 19, 2023, 04:16:55 pm
content: This question is mainly about mixed signal and digital design PCBs that use ASICs, FPGAs, MCUs, DDR RAMs, MGBTs e.t.c.For power and signal integrity one thing we can measure is the oscillation of the signal or power rail of interest. This could be done using oscilloscope where the bandwidth of the scope + probe needs to be quite large, depending on the rise time of the signals involved and the clock frequency of the device of interest. However, there are other devices that could provide information as well from a different perspective. One of these is the vector network analyser (VNA) that can help to extract S parameters for the circuit topology of interest. What other hardware kits do people that do SI and PI analysis use?

author: pdenisowski
author_rank: Super Contributor
timestamp: July 19, 2023, 09:06:51 pm
content: In my experience, it's mostly just scopes and VNAs.

author: electron_plumber
author_rank: Regular Contributor
timestamp: July 21, 2023, 05:05:20 pm
content: Don't forget these for power integrity:thermal camerae-load or load box of some kind for transient response testingbode plotter + isolation transformer for loop response analysis (assuming you're using constant frequency DC-DC controllers) and impedance measurementsa current probea high bandwidth differential probe is useful if you can afford one (nice for characterizing those high-side gate waveforms)Lately I've also been using LCR meters more often to characterize harness inductance at the system interface, so I can confirm my assumptions about input filter damping.

author: pdenisowski
author_rank: Super Contributor
timestamp: July 21, 2023, 07:16:20 pm
content: Well, if we're including accessories like current probes for power integrity, then I would include a deskew fixture as wellAnd if you include EMC in power integrity testing, then you might also want a LISN, near field probes, etc.

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: August 03, 2023, 11:28:31 am
content: By the way, talking about PI, if we want to check performance of our SMPS, we would need to connect it to a load. Now there are special pieces of equipment called electric load which are bench top equipment that can be used for this purpose. The thing is, we would need to connect to them using a harness. A long harness has its own inductance as well. So what really does an electric load help in measuring when we can't measure the response speed of the SMPS due to the long harnesses that connect the SMPS on PCB to the bench top electric load?

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2023, 05:12:16 am
content: Quote from: matrixofdynamism on August 03, 2023, 11:28:31 amEload lead issues if any are dealt with by the load's remote sensing.

author: electron_plumber
author_rank: Regular Contributor
timestamp: August 06, 2023, 02:49:26 pm
content: Remote sensing won't help with the lead inductance. If you're trying to hit a certain di/dt during load-step testing, you may need to reduce the inductance of your test setup by using shorter/twisted leads. Having said that, most electronic loads are fairly limited on the maximum di/dt they can achieve during load steps, even with a short low-inductive test lead.So, what I often do for transient testing and short circuit testing (which is when the inductance matters) is use a resistive load with an inline FET that I can drive with a function generator. This allows me to hit a higher di/dt than my bench-top electronic load.