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I have a question about eval board schematics of STMP1.

I noticed that zero ohm resistors were used in the PMIC reference circuit.

Why these resistors used in series to the power lines? Need I them really?

enter image description here

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  • \$\begingroup\$ See electronics.stackexchange.com/questions/385940/…. \$\endgroup\$ – Transistor Jan 22 at 14:14
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    \$\begingroup\$ It saves taking a scalpel to the PCB when working on it, debugging, or measuring current consumption of some sub-unit. \$\endgroup\$ – Brian Drummond Jan 22 at 14:26
  • \$\begingroup\$ Do you need them? Hmm; will the device work if they are not iinstalled? ;) \$\endgroup\$ – Kaz Jan 22 at 22:43
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Why these resistors used as series to the power lines? Need them really?

If you have multiple circuits teeing off the same power rail and the overall circuit is quite complex, there is a good reason for putting zero ohm links in series with the individual power feeds and that reason becomes apparent when fault finding.

If one circuit is dragging the whole power rail down (due to a shorted sub-circuit somewhere), having zero ohm links helps to track down the fault because they are easily removable, easily replaceable and cheap.

Personally if the individual load current requirements are moderate and you could bear the cost of a 0.1 ohm resistor (instead of zero ohms) you could probably identify the rogue sub-circuit using a DVM across each zero ohm link. Bear also in mind that zero ohm links might be sufficiently "resistive" to facilitate this nicety.

The Vishay CRCW zero ohm link has a maximum resistance of 0.02 ohms so I suspect it could be somewhat relied upon to be about 0.01 ohms. 2 amp through 0.01 ohms is a volt drop of 20 mV and very easily seen on a modern DVM.

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  • \$\begingroup\$ Upvote but I think it's worth mentioning that these are a good idea on the first revision or two of a PCB, but can often safely be removed once the design is sufficiently validated - if saving a few cents and mm^2 per board is important. \$\endgroup\$ – pericynthion Jan 22 at 17:35
  • \$\begingroup\$ They help diagnose faults in the field or in production so it’s probably not all that wise to remove them. \$\endgroup\$ – Andy aka Jan 22 at 17:37
  • \$\begingroup\$ OK, fair point! \$\endgroup\$ – pericynthion Jan 22 at 17:59
  • \$\begingroup\$ Thank you, I decided to connect a series of resistors as well :) \$\endgroup\$ – Gokhan Sahin Jan 23 at 4:23

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