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How VPS* helps find ground plane shorts (*Vector plane stimulus)

How VPS* helps find ground plane shorts (*Vector plane stimulus). PolarInstruments.com. Toneohm help locate shorts - After ATE or flying probe test has isolated a faulty net. Short circuit and bus fault location - Simple trace to trace or - Multilayer plane / trace or plane / plane.

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How VPS* helps find ground plane shorts (*Vector plane stimulus)

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  1. How VPS* helps find ground plane shorts(*Vector plane stimulus) PolarInstruments.com

  2. Toneohm help locate shorts - After ATE or flying probe test has isolateda faulty net. Short circuit and bus fault location- Simple trace to trace or- Multilayer plane / trace or plane / plane Overview

  3. How do you deal with an ATE printout that lists 50 components on one node all short to 50 components on another? E.G. a Vcc +5V short to Gnd? Or a Trace to plane short? Tools for post ATE faultfinding

  4. Milliohm measurement For bus leakage non invasive track current measurement... Contact Or non contact For simple track shorts û

  5. Present a new set of challenges The short (or bus fault) has to be located in two dimensions So what how can a VPS equipped Toneohm help? Plane to plane shorts...

  6. Surprisingly most plane shorts occur during assembly.... Without a 950 they can be difficult to find they are assumed to be “internal” However 90% are assembly related and Easy to repair Are plane shorts worth repairing?

  7. From a quality standpoint it is important to know why the plane short has occurred... Is it a thermal cause? a layout problem? a latent defect with the PCB? Why not throw away boards with plane shorts?

  8. How? – The next slides tell you how VPS works

  9. First imagine a track to ground short Ground Plane

  10. VPS also works for plane to plane shorts Track Ground Plane

  11. The unknown short circuit is a position û Track û Ground Plane Short

  12. VPS Injects a current across the plane I+ Track û Ground Plane Short I-

  13. This sets up a potential gradient across the PCB I+ Track +3 û Ground Plane +2 Short I- +1 0 -1 -2

  14. Measure voltage between short and plane position.The track simply acts as an extension of the meter lead I+ Track +3 û Ground Plane +2 Short I- V1 +1 0 -1 -2

  15. The short is somewhere along the line where V=0. I+ Track +3 û Ground Plane +2 Short I- V1 +1 0 -1 -2

  16. Inject the current at right angles to locate the second dimension. This has isolated the short in one dimension.

  17. By injecting at right angles.. I+ Track +3 Ground Plane û +2 Short I- V2 +1 0 -1 -2

  18. Now find where V2 = 0 I+ Track +3 Ground Plane û +2 Short I- V2 +1 0 -1 -2

  19. The short is located where V1 + V2 = 0 I+ Track +3 Ground Plane û +2 Short I- V +1 0 -1 -2

  20. By looking at the polarity of V1 and V2 the 950 can display directional arrows on the front panel that guide you to the area of the short I+ + + Track +3 + - Ground Plane - + û +2 Short - - I- V +1 0 -1 -2

  21. The 950 Plane shorts mode uses this VPS technique to helpyou rapidly locate plane to plane shorts, A 950 givesa continuous display of short direction while you probe and the current injection is switched automatically I+ + + Track +3 + - Ground Plane - + û +2 Short - - I- V -2 +1 0 -1

  22. Your Toneohms pay for your investment very quickly

  23. USA / Canada - Polar Instruments Inc(800) 328 0817 - Richard Smith UK Polar Instruments (UK) Ltd023 9226 9113 - Paul Norrington Asia / Pacific Polar (Singapore)+65 873 7470 - Amit Bhardwaj R.O.W. - Polar Instruments LtdTel: +44 1481 253081- Martyn GaudionEmail all offices: mail@polarinstruments.com Toneohm short and bus fault locators Ó Polar Instruments 2001 All trademarks recognized

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