How do Differential Solder-In Probes work? - Page 1
Forum section: electronics / projects

author: bhj99
author_rank: Contributor
timestamp: August 16, 2023, 12:36:59 am
content: Hi all, I wanted to get some advice regarding the use of differential solder-in probes. One of my colleagues suggested using this instrument to measure voltage drops at decoupling capacitors as part of a PDN measurement analysis for all the power rails on a PCB design. Sample part number is shown in the link. Anyone have experience with doing power verification testing or how to go about doing test cases using this sort of probe?https://www.keysight.com/us/en/product/N5381B/infiniimax-ii-differential-solder-in-probe-head-12-ghz.html

author: Someone
author_rank: Super Contributor
timestamp: August 16, 2023, 02:26:22 am
content: Unlikely to be useful for measuring voltage drops due to the system DC accuracy, they're generally more for noise/ripple. Great for seeing the ripple in some corner of a necked down/swiss cheese power plane.

author: bhj99
author_rank: Contributor
timestamp: August 16, 2023, 02:13:07 pm
content: Do you happen to have resources that show you how to use this type of probe?

author: CaptDon
author_rank: Super Contributor
timestamp: August 16, 2023, 02:22:48 pm
content: My experience with solder-in is that they were designed for the GHZ frequency range and EASILY destroyed by overvoltage and cost as much as my recent used car purchase. Speaking about our Tektronix probes we use for generating the EYE patterns on high speed differential data lanes.We have a couple of dead ones at $6 Kilobucks each and Tek wants about $5000.00 each to fix them!!! Who ever thought an oscilloscope would cost upwards of $250,000.00?(And still alias like hell when a high frequency signal is keyed by a much lower frequency signal)

author: tszaboo
author_rank: Super Contributor
timestamp: August 16, 2023, 02:38:14 pm
content: You are measuring in-situ with the designed-in power supply powering it. This is not a VNA based PDN measurement.Basically if you have a device with large current usage, like an FPGA, you make the FPGA switch it's output switch at the same time and look for dips on the power line. Why solderable probe? No idea, probably laziness, or the test takes a long time.These are made for differential active probes. That 900 USD device is just the adapter for the probe, the probe can be anywhere from 3000 USD, but considering it's 12GHZ, probably more like infinity money.Do you really need this?

author: jonpaul
author_rank: Super Contributor
timestamp: August 16, 2023, 02:57:39 pm
content: Unclear your problem or objectives.99% of our decades of SMPS design/debug/prod were done with 100...500 MHz scopes and Tel x10 probes or current probes/CT (rarely)Never needed ANY digff probe measurements.Use a mains iso xformer.Read Tektronix Circuit Concepts "Oscilloscope probe circuits" from 1960ss still excellent.https://www.w140.com/tekwiki/index.php/Concepts_Series062-1146-00 Oscilloscope Probe Circuits062-1120-00 Probe MeasurementsSee section on diff probes.Send schem or pix exactly what you seek to measureJon

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 16, 2023, 02:58:32 pm
content: Start by stating with which frequency range you are interested in.If it is not too extreme, I guess you can do a lot by clamping a matrix board to your DUT and put some custom circuitry on it. Make some simplified FET probes or use standard RF gain blocks. Maybe even add a MUX and a uC to control it. You can spend a day or two tinkering on this for the cost of such a probe, and your custom solution may fit your use case better.

author: Someone
author_rank: Super Contributor
timestamp: August 17, 2023, 12:01:19 am
content: Quote from: bhj99 on August 16, 2023, 02:13:07 pmSolder to component/pads, connect other end to scope?There are documents on such a apparently boring topic:https://prc.keysight.com/Content/PDF_Files/5992-3350EN.pdf"Probe soldering guidelines for Keysight InfiniiMax probes"

author: Smokey
author_rank: Super Contributor
timestamp: August 17, 2023, 12:43:11 am
content: Is there an active element right at the tip (on that little PCB with the solder in wires)? or is all the magic in the probe body?If that tip is just a little PCB, a few passives, and some wires, that's not much stuff for $863 USD.

author: alm
author_rank: Super Contributor
timestamp: August 17, 2023, 01:47:09 am
content: Quote from: Smokey on August 17, 2023, 12:43:11 amI believe most of them are just some passives, connectors and maybe a resistive PCB trace and fancy PCB substrate. I doubt it costs anywhere near $863 to make, but it's an accessory to an expensive probe, and I don't think anyone else is making the tips. So what else are you going to do? Buy equally expensive probes and tips from a competitor, which will also require you to switch scopes? Live with lower bandwidth probes? Make your own?

author: Someone
author_rank: Super Contributor
timestamp: August 17, 2023, 01:53:51 am
content: Quote from: Smokey on August 17, 2023, 12:43:11 amLow volume product that has complex qualification/testing/calibration requirements, yep that's gonna be expensive.If it's such a juicy mark up, no doubt you'll be able to setup a business to undercut that and still profit.