Are PCB of LM3886 correct?

[gengcard]

I made a PCB follow as Carlosfm's circuit but I am not sure whether some parts are put in correct positions. Please help me to check the PCB. Thank you.

 

[gengcard]

This picture is shown the circuit is used.

 

[Mick_F]

The supply bypass caps are way too far from the chip. Also, It is preferrable to separate signal and power ground. I am not sure about the use of a ground plane anyway - I prefer star grounds.

Mick

 

[CJ900RR]

The supply bypass caps are way too far from the chip. Also, It is preferrable to separate signal and power ground. I am not sure about the use of a ground plane anyway - I prefer star grounds.

Mick

I seccond that...

 

[jackinnj]

The supply bypass caps are way too far from the chip. Also, It is preferrable to separate signal and power ground. I am not sure about the use of a ground plane anyway - I prefer star grounds.

Mick

No ground plane -- you can use a 100 - 150 mil trace to connect the reservoir caps to the star.

 

[gengcard]

Thank you everyone for comments.

Can you please tell me the adventage of star ground?

 

[zenon]

can you please post the original file, I'm trying to learn the eagle software.

 

[gengcard]

Hi zenon,

Do you have LM3886T in your library? If no, I'll attach my library to you.

 

[CJ900RR]

Thank you everyone for comments.

Can you please tell me the adventage of star ground?

Yes. Read the datasheet for the LM3886, page 19

 

[jackinnj]

Thank you everyone for comments.

Can you please tell me the adventage of star ground?

The star ground prevents "current loops" which occur on a ground plane. Current loops exist since -- the resistance of the copper foil isn't perfectly uniform and the distances between points of current flow are variable -- when current flows you have an electromagnetic effect -- radiation of energy -- small in the case of analog circuits -- very large in switch mode power supplies -- these differential currents get magnified by the amplifier chip and "whoops" you have a problem. There was a neat article in EDN magazine, the July 6th issue by a fellow from Analog Devices with pictures which better describe what my verbiage fails to do.

Try to keep all your grounds on one side of the printed circuit board -- i usually have the power traces on the bottom, signal traces on the top. If you have to make a connection between two layers on a power or ground trace you might want to widen the trace and punch several vias through so that there's enough copper on the plated-through via to prevent it from acting like a fuse.

You want to be careful in not running the ground from the input pin too far to the star -- by means of capacitative coupling it can pick up RFI.

 

[tcpip]

I want the Eagle library part for 3886

Do you have LM3886T in your library? If no, I'll attach my library to you.

Can you please post an attachment with the LM3886 Eagle library part? I have the LM3875, but not the 3886, and I'd rather use a library part someone's used and tested.

Thanks.

 

[Roushon]

eagle library

I did not find the schematic version for LM3886 in Eagle library. But for the board version Library: linear and package:SIP11 works well.

 

[tcpip]

Re: eagle library

I did not find the schematic version for LM3886 in Eagle library. But for the board version Library: linear and package:SIP11 works well.

It's risky to use just a SIP component instead of an amp for making schematics and PCBs, I feel. And of course the NS Overture amps are not part of the Eagle standard libraries. I was hoping some of the people on this forum who have designed PCBs using Eagle for the Gainclone chips will have defined library components for these amps and will give me this definition. Someone gave me the LM3875 this way more than a year back on this forum.

 

[Roushon]

It is risky in what sense? I have checked the pins and the overall dimension in the board version library and they are correct. But of course one cannot make a schematic around lm3886 and then convert it into board in Eagle if one does not have the schematic for lm3886 in the library.

 

[CJ900RR]

Scroll down on this post and you will find the lbr-file for the 3886 and 3875: http://www.diyaudio.com/forums/showthread.php?s=&threadid=59335&highlight=

 

[zenon]

does someone have the file for the LM4780?

 

[CJ900RR]

does someone have the file for the LM4780?

It's to be find here: http://www.diyaudio.com/forums/showthread.php?s=&threadid=30864

BTW, this forum has a search-option

 

[gengcard]

Hi all,

I attach my audio amplifier eagle library in this thread. I think my library will be helpful for you. I don't think I perfectly created them but they are fine for me.

1. LM3875
2. LM3886
3. OPA549T
4. OPA549S

I wish you are enjoy to the file.

 

[gengcard]

can you please post the original file, I'm trying to learn the eagle software

Here is the original file as your requirement. When you use my file you must change connectors in file to your formatt.

 

[gengcard]

Thank you jackinnj and CJ900RR for both comments

I wanted to make my PCB by double layer but the PCB maker who I presently order can't make a perfect PCB double layer. It's the cause I must design one layer PCB. However, I will modify the ground to be star ground for one layer PCB as you all comments.

Thanks a lot.