Help with understanding l ayers, please.

Am 27.10.2016 um 19:57 schrieb Martin Rowe:

Hi,

 

I wish to work with a ST-Microlelectronics TDA7491HV. Which, if my

understanding is correct has a PowerSSO-36EPD or PSSO-36SD (or some other

combination of letters - depending on reference source!) footprint or

package.

 

As I have very little experience  in this skill area, I went looking for an

example on the web and found one at

http://www.diymodules.org/eagle-show-object?type=usr&id=101499&part=Audio-Power-amlifier+V.2.0.lbr&package=PSSO-36SD#preview

(an extract of this device is attached).

 

My question is this: What is the function of the rectangles on Layer 19

(Unrouted) sitting over the pads?

 

Is it likely to be a mistake and they should in fact be be on Layer 29

(tStop). However, if that is the case, the size is too small.

 

I'm confused...

 

Regards, Martin

 

I don't see the stripes in the library. IMHO it would be better if you

attach the board file here, so we can analyse it.

--

Mit freundlichen Grüßen / With best regards

Joern Paschedag

Joern Paschedag wrote on Fri, 28 October 2016 08:16

I don't see the stripes in the library. IMHO it would be better if you

attach the board file here, so we can analyse it.

Yes, of course, sorry. I have had to ZIP my sample board, it to get under

the 50kb limit. hope that that does not cause yet more problems?

My concern, I think, is my understanding of the function of the Unrouted

Layer.

What is the relationship between Layer 19 and the (incredibility difficult

to find!) Unrouted Airwires that are presented following the Ratsnest

function?

Is the Unrouted Layer in some way related to the Auto-routing process?

Does the Auto-router move Wires defined in the schematic, back and forth

between coper layers and Unrouted Layers? And if so, what is the purpose

(advantage?) of specifically placing items on the Unrouted layer?

Sorry if the above sounds like the ramblings of the confused....

Regards, Martin

--

Ver 7.6.0 Linux (64bit)

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

It looks like the author of the LBR made a mistake by putting marks on the

pads in the Unrouted layer (#19) that should be in tDocu (#51). The copper

planes also are not completely filled in under the chip because the author

put circles in the Dimension layer (20), instead of tPlace (#21). As far as

I can tell from the data sheet, these are molding marks and not holes in

the chip.

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

Am 28.10.2016 um 14:11 schrieb David Pollum:

It looks like the author of the LBR made a mistake by putting marks on the

pads in the Unrouted layer (#19) that should be in tDocu (#51). The copper

planes also are not completely filled in under the chip because the author

put circles in the Dimension layer (20), instead of tPlace (#21). As far as

I can tell from the data sheet, these are molding marks and not holes in

the chip.

 

The library is not correct as David mentioned already.

I don't know if I understand correctly your "trouble" with the unrouted

"layers".

This is just a "level" where yet unrouted  connections are shown.

One must have the possibility to show or hide layers and that goes for

unrouted as well.

If  you have problems to see the unroutes wires you can easily change

their color or turn off all other layers.

--

Mit freundlichen Grüßen / With best regards

Joern Paschedag

Hi Joern and David,

Thank you both for your advice. I now have to confidence to go ahead and

modify my copy of the downloaded library.

I think it is safe to assume that: "There is no logical reason to PUT items

on the Unrouted layer - The content of the unrouted layer is managed by the

application".

Best regards, Martin

--

Ver 7.6.0 Linux (64bit)

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

Hi Joern and David,

Thank you both for your advice. I now have to confidence to go ahead and

modify my copy of the downloaded library.

I think it is safe to assume that: "There is no logical reason to PUT items

on the Unrouted layer - The content of the unrouted layer is managed by the

application".

Best regards, Martin

--

Ver 7.6.0 Linux (64bit)

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

Martin Rowe schrieb:

Thank you both for your advice. I now have to confidence to go ahead and

modify my copy of the downloaded library.

 

I think it is safe to assume that: "There is no logical reason to PUT items

on the Unrouted layer - The content of the unrouted layer is managed by the

application".

No - it is safe to assume that: You can /never/ trust any library from

someone else. This includes those that come with EAGLE.

Often it's even faster to create a needed part by yourself than trying

to correct a downloaded one - which still includes some risk that you

overlook something and later get in trouble.

Tilmann

Martin Rowe schrieb:

Thank you both for your advice. I now have to confidence to go ahead and

modify my copy of the downloaded library.

 

I think it is safe to assume that: "There is no logical reason to PUT items

on the Unrouted layer - The content of the unrouted layer is managed by the

application".

No - it is safe to assume that: You can /never/ trust any library from

someone else. This includes those that come with EAGLE.

Often it's even faster to create a needed part by yourself than trying

to correct a downloaded one - which still includes some risk that you

overlook something and later get in trouble.

Tilmann

On 29/10/16 08:16, Tilmann Reh wrote:

Martin Rowe schrieb:

 

I think it is safe to assume that: "There is no logical reason to PUT items

on the Unrouted layer - The content of the unrouted layer is managed by the

application".

 

No - it is safe to assume that: You can /never/ trust any library from

someone else. This includes those that come with EAGLE.

 

In fairness, I think Martin's statement is probably a decent enough rule

of thumb as well. But Tilmann's version is a useful adjunct to the more

generic "never trust anything you find on the Internet".

On 29/10/16 08:16, Tilmann Reh wrote:

Martin Rowe schrieb:

 

I think it is safe to assume that: "There is no logical reason to PUT items

on the Unrouted layer - The content of the unrouted layer is managed by the

application".

 

No - it is safe to assume that: You can /never/ trust any library from

someone else. This includes those that come with EAGLE.

 

In fairness, I think Martin's statement is probably a decent enough rule

of thumb as well. But Tilmann's version is a useful adjunct to the more

generic "never trust anything you find on the Internet".