Uwharrie Test Solutions

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What's Killing my Vector Based Test?

Most every digital and hybrid model developed by Uwharrie Test Solutions is verified many times over for repeatability. They are also tested  in as many different configurations as practical. Power supplies and test-step frequencies are margined, faults are injected, loads can be added.

The only thing that I cannot do, without an additional budget, is to debug it on your fixture and your UUT. Therefore, to assure some customer satisfaction I choose to give out as much free advice on my web site as possible. This way the end user (my customer or not) can make these tests function.

The model worked stand-alone, so why won't this test work in my fixture?

I have listed some of the most common answers to this question.

  • You did not properly isolate the device. Back-driven parts should be inhibited, oscillators shut off, connected buses must be disabled.

  • Too many probe-wires. Are you Kelvin Testing those series resistors on high speed digital signals?

  • Your fixture is mis-wired.

  • Your tester has a shorted relay or some other malfunction.

  • The device you are testing is not correctly powered or it's on an Isolated Ground Net.

  • The GND relay in the PWRUP() subroutine was never closed. Did this line get deleted by mistake?

SET PIO(0) HRLY(CLOSE 3);

  • Your device is powered by an On-Board Power Supply that is noisy.

  • The DUT on your sample board is simply a bad part.

  • Your UUT fab is bad.

  • Your artwork has a layout error.

  • Your artwork is the wrong version.

  • Your DUT is the wrong version.

  • Your DUT is mis-installed, or just missing.

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