Need help with LTC3129 linear part

Question

I am working on a circuit using the LTC3129 and would like to lay out a pcb using eagle. Can someone either generate the library or give me some hints on how to generate using ulp? Bill

dukepro · Answer

On 02/03/2014 12:35 PM, zmrbill wrote:

I am working on a circuit using the LTC3129 and would like to lay out a
pcb using eagle. Can someone either generate the library or give me
some hints on how to generate using ulp?

Good morning, Bill,

A User Language Program is not the right tool to generate this part.

All in all, it is a read-only environment and can not directly change

anything in the schematic, board, or library editors. That being said,

it can exit the program passing a string argument as a parameter to

exit() that contains a script to execute. The script can do anything

that you can type in the command text box.

I took a quick look at the datasheet for the LTC3129. The best place to

start is in the library editor with a personal library opened. It is

recommended to avoid editing any of the libraries that came with the

distribution - the changes will likely be overwritten by updates and

upgrades.

First, with the library editor open, create a new symbol that closely

matches the block diagram on the first page of the datasheet. Make sure

that the pins you add have the proper direction. PWR is for power and

ground pins. IN and OUT signify the direction of the flow of power or

signal. The ERC will warn you if you have more than one OUT on a net,

or if a net contains one or more IN's without an OUT. You can read more

about the characteristics of each direction in the manual.

Next, create a package that accommodates the footprint of the '3129.

Page 2 of the datasheet shows that this part is offered in two different

packages - a QFP and an MSOP. A suitable package may exist in

smd-ipc.lpr. If you find one there, you can drag it from the control

panel to the library editor to include it in your library. Don't forget

to add the center pad on the bottom of the chip. Pages 26 and 27 of the

datasheet has the recommended pad layouts.

Finally, create a new device for the '3129. Add the symbol you created

in the first step, and the package you copied or created in the second

step. Use the CONNECT to connect the pins on the symbol to the pads on

the package.

Save the library. Go back to your schematic and USE the library, then

UPDATE the library. At this point, you should be able to ADD the new

part to your schematic.

It is a good idea to know how to create your own parts. While the

libraries included in the distribution are extensive, they are far from

complete, and at the rate new parts are being invented, they will never

be complete. Additionally, there is no guarantee for accuracy on any of

the distribution libraries. Always verify the package against the

datasheet. I have had boards fabricated on more than one occasion that

wound up useless because I didn't check the layout.

There is more information on this process in the user manual and in the

tutorial. Look in the doc/ directory below Eagle's installation directory.

I hope this helps get you started.

Regards,

- Chuck