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Measurements >> Other Measurements >> Connecting oscilloscope to ASIC test pad
https://designers-guide.org/forum/YaBB.pl?num=1319576337

Message started by simdes on Oct 25^th, 2011, 1:58pm

Title: Connecting oscilloscope to ASIC test pad
Post by simdes on Oct 25^th, 2011, 1:58pm

Hello, I'm designing my first IC. There will be four ring oscillators running on 400 - 450 MHz and some others modules. Two of them will be in PLL and two will be enabled and free running. The signals form the oscillators would be internal only. I think that's good idea to do buffered (with EN) test pads connected to the oscillators for debug purpose to see if they working (oscillators). In my university J have access to very poor equipped lab with the probe station, agilent B1500A semiconductor device Analyzer, oscilloscope, and few others... There are only DC probes, no RF probes or network analyzer. So I thinking connecting this oscilloscope to test pads on wafer. Any suggestions how? They can spend some money on my project. My idea is to buy basic RF probe + coax cable and connect directly to the oscilloscope. Will that work? The ASIC will be bonded directly to the printed board, so mayby better bond these pads to printed board and there probe them with oscilloscope in conventional manner, but this will degrade signal... and there's little space on PCB around die...

Title: Re: Connecting oscilloscope to ASIC test pad
Post by loose-electron on Oct 27^th, 2011, 5:06pm

you probably want to build a dedicated (external to the IC) circuit on the PCB so that you can directly drive a 50 ohm coax.

include methods to calibrate that circuit out of the measurements.