LM4780 Single side PCB

bill1961 · 29th January 2005, 05:04 PM

This is my first try to make a single side pcb for LM4780.
I'm using the following schematic, (from National website).
[IMG]D:\PCB's\LM4780\schematic.gif[/IMG]

I've got no much experience about pcb making, so please make your comments, post your advise, about my pcb.
[IMG]D:\PCB's\LM4780\pcb.gif[/IMG]

Netlist · 29th January 2005, 05:07 PM

Bill,
welcome.
Instead of trying to post the picture with the IMG button, try inserting the path into the 'Attach file' box.

/Hugo

bill1961 · 29th January 2005, 05:35 PM

OK, this is the schematic

bill1961 · 29th January 2005, 05:41 PM

And the pcb

peranders · 29th January 2005, 05:49 PM

The high current traces are rather thin. If you check the datasheet you can get a picture of how much current you can get. 23 A may occur as short circuit current.

Kevin Haskins · 30th January 2005, 03:21 AM

I don't know from personal experience how critical it is but you will notice that National separated the power & output ground plane from the low level signal input ground plane via a 2.7 Ohm resistor. This may help keep noise out of the input.

Also... lead length & width for the high current traces is important. I'd try and add some width to them from the pins to the two big caps. Also... you may want to add some more capacitance. I see your running it in parallel and 2000uF isn't much. National also suggest 10uF OR bigger for the smaller electrolytic bypass. I've only used 10uF with my board (and it works very well) but I plan to experiment with larger values.

I'm not sure how you plan on mounting this to the heatsink but having the one edge of the PCB flush for easy surface mounting makes life a little easier.

Just for space constraints I left the 1.0uF input cap off the board. The good quality MKP caps are large in relation to the board size and I've always just used leaded caps on the input RCAs if DC blocking was needed.

bill1961 · 30th January 2005, 06:11 AM

Is it better now?

bill1961 · 30th January 2005, 10:51 AM

A new version of the schematic to include a 2.7Ohm to seperate signal ground from power ground plane. Also added more cappacitance (2200uF). All, thanks to Kevin's suggestions.

Upupa Epops · 30th January 2005, 11:07 AM

To signal ground you must connect also shunt resistors from input and feedback resistors - not only ground of input connector

.

bill1961 · 30th January 2005, 11:59 AM

? shunt resistors from input and feedback resistors

Could you be more specific please?

29th January 2005, 05:04 PM	#1
bill1961 diyAudio Member Join Date: Sep 2004 Location: GREECE	LM4780 Single side PCB This is my first try to make a single side pcb for LM4780. I'm using the following schematic, (from National website). [IMG]D:\PCB's\LM4780\schematic.gif[/IMG] I've got no much experience about pcb making, so please make your comments, post your advise, about my pcb. [IMG]D:\PCB's\LM4780\pcb.gif[/IMG]

29th January 2005, 05:49 PM	#5
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	The high current traces are rather thin. If you check the datasheet you can get a picture of how much current you can get. 23 A may occur as short circuit current. __________________ /Per-Anders (my first name) or P-A as my friends call me

30th January 2005, 03:21 AM	#6
Kevin Haskins diyAudio Member Join Date: Mar 2004 Location: Port Angeles, WA	I don't know from personal experience how critical it is but you will notice that National separated the power & output ground plane from the low level signal input ground plane via a 2.7 Ohm resistor. This may help keep noise out of the input. Also... lead length & width for the high current traces is important. I'd try and add some width to them from the pins to the two big caps. Also... you may want to add some more capacitance. I see your running it in parallel and 2000uF isn't much. National also suggest 10uF OR bigger for the smaller electrolytic bypass. I've only used 10uF with my board (and it works very well) but I plan to experiment with larger values. I'm not sure how you plan on mounting this to the heatsink but having the one edge of the PCB flush for easy surface mounting makes life a little easier. Just for space constraints I left the 1.0uF input cap off the board. The good quality MKP caps are large in relation to the board size and I've always just used leaded caps on the input RCAs if DC blocking was needed. __________________ www.diycable.com

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29th January 2005, 05:07 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Bill, welcome. Instead of trying to post the picture with the IMG button, try inserting the path into the 'Attach file' box. /Hugo

30th January 2005, 11:07 AM	#9
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	To signal ground you must connect also shunt resistors from input and feedback resistors - not only ground of input connector .

30th January 2005, 11:59 AM	#10
bill1961 diyAudio Member Join Date: Sep 2004 Location: GREECE	? shunt resistors from input and feedback resistors Could you be more specific please?

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