Having worked as a micro section technician, IPC Certified to 6010, 6011, 6012 and 6013, I've seen a lot of changes to PCB's over the years. During the development of a board some components may be included for testing and calibrating. When a final design is established there are two choices: Modify the schematic or modify the board. To change the schematic you simply need engineers to make the necessary changes to the file and change the revision (up one level - usually) as well as the BOM (Bill Of Materials). But to change the board itself you need to revise all the silk screening and the layers of the board (circuit traces). Solder mask also needs to be changed. All that means a whole new setup for the machinery involved and new lithographic's. From a cost standpoint - it's easier to say DNP on R334 than to completely rebuild the board.

On some "Universal" boards, the way they are configured can mean using the same PCB Layout but installing only certain components while other parts of the board may remain unpopulated. I've seen this with PLENTY of communication boards where a single design board can be configured to work in several different applications. To include DNP on ALL the unpopulated parts would be time consuming and costly. And MANY other boards have spaces for components that were never installed. At one point they may have been a part of the design but with revisions those parts may have been replaced by other component values elsewhere and R334 is no longer needed.

 

. From a cost standpoint - it's easier to say DNP on R334 than to completely rebuild the board.

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I can see in many instances a reason, but in this case it is just changing the value of a single resistor, in place of having two, both in parallel!.
Max.

 

DNP is one standard abbreviation we use to indicate a component in the artwork that is not used. May be other terms too but none come to mind this morning.

AOT is a new one, it may be British usage. We use SAT for Select At Test for the same thing. There may be a initial value placed at assembly, or not, either way it should be specified, along with a range of possible values, and a method of selection.

More often than not engineering just tossed the documents over the wall without a range or method to determine the final value and leaves it to test to stick something in there that works.

Welcome to the real world.

 

How about "Do not pontificate" lol

That's another good one!

 

Hola Max,

Never used any IC where the application said so but I run across some of their documents.

It means "do not populate" as opposed to "populate".

/Edit
Forgot to upload example - Point 2.1.4
Edit/

 

But why would you include them in a final print and board outline?
Max.

Multiple variants of the same layout is the usual reason.

 

I think we have thrashed out the definition of DNP in this instance, and the reason for its use.
It is just the example of apparent obsolescence of using it in the Microchip board referenced by paralleling two resistors, one marked DNP.
Instead of updating the rev box with a new value for a single component?
Which I think would be the typical method.
Max.

 

I think we have thrashed out the definition of DNP in this instance, and the reason for its use.
It is just the example of apparent obsolescence of using it in the Microchip board referenced by paralleling two resistors, one marked DNP.
Instead of updating the rev box with a new value for a single component?
Which I think would be the typical method.
Max.

Yep, another horse beat to glue!

 

Makes sense, but they left a spot for R2, R4 but none for C3!
http://ww1.microchip.com/downloads/en/DeviceDoc/51793a.pdf
Max.

It's different version between schematic(103-00124) and PCB(102-00124)