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I have some experience with highfrequency circuit analysys. However I am a newbie in PCB design. I am analysing this circuit: http://www.ti.com/lit/ug/spmu365b/spmu365b.pdf (starts on page 36) and regularly see things like "OMIT" for headerpins or components like resistors or so.

e.g.:

  • p41 (6/6): the boxheader(?) on the left.

  • P40 (5/6): R48 on the dev board are two small surfaces with some soldering on it but no component apparently. I can hardly see myself (de)soldering resistors on my new dev board...

Why is this being mentionned? What do the people who made the PCB mean by this?

I mean if this part has to be omitted, why did they even place it on the PCB?

Thx

LandonZeKepitelOfGreytBritn
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    similar question : http://electronics.stackexchange.com/questions/138378/why-does-there-seem-to-be-a-missing-component-in-many-pcbs?rq=1 – Marla Jul 11 '16 at 15:40
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    You might hardly see yourself desoldering resistors on dev kits, I do it frequently when trying to evaluate different options for a component. – Tom Carpenter Jul 11 '16 at 15:45
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    Also very similar to: http://electronics.stackexchange.com/q/112258/25328 – Tut Jul 11 '16 at 20:06

1 Answers1

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Extra/omitted parts on a PCB can be very useful for

a) Having multiple versions of a circuit able to be built with only one PCB

b) Debugging, when I lay out an RF board I often put an omitted 1k SMD resistor from the line finishing near to a ground pad. Invaluable to solder a 50ohm coax to for probing the signal on the line, with good RF integrity and without damaging the line. A JTAG or RJ45 socket may be handy for digital access to a board for debug, but is not needed in production, it's omitted for cost or because it won't fit in the final production case.

c) You may often see a 0 ohm resistor in series with a power line, for monitoring current, or isolating parts of the circuit. These pads may also have a trace under them to short them in the normal case, the trace can be cut to use the component.

Neil_UK
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