LM3X7 Supply

Hi,
add the low value compensation capacitors specified by the manufacturer and fit them VERY close to the regulator pins.

Disconnect the smoothing capacitor zero volts line from the ground sense line of the regulator.
Take the smoothing cap zero volt line direct to the output ground point.

R3 may need to be lowered to 120r to ensure sufficient current flow through the regulator if the output draws zero current.

What does the manufacturer say about protection diodes across C5 & C6?
 
Caps (0,1uF) for improved ripple rejection i,ll add directly to the pins "under the board".

Disconnect the smoothing capacitor zero volts line from the ground sense line of the regulator.

This i do not understand and could find anything similar in the datasheet so for now,, i did nothing like that.

Protection diods across C5, C6 is not needed for this application AFAIK..

Trimmer pots are 4k7 and not 47k.. thanx for pointing that out :)

Thanx for support !

/Zei
 
zei said:
Disconnect the smoothing capacitor zero volts line from the ground sense line of the regulator.
Take the smoothing cap zero volt line direct to the output ground point.

This i do not understand and could find anything similar in the datasheet so for now,, i did nothing like that.
because almost everyone uses software to draw the schematics and the software assumes that wires have zero impedance.
Do not connect any current carrying wire to the voltage sense part of the regulator. This applies to both the +ve voltage sense and the -ve voltage sense.
 
AndrewT said:
Disconnect the smoothing capacitor zero volts line from the ground sense line of the regulator.
Take the smoothing cap zero volt line direct to the output ground point.

zei said:

...
This i do not understand and could find anything similar in the datasheet so for now,, i did nothing like that.
...
/Zei

It's important. I tried to explain the underlying concepts in Post #178, here:

http://www.diyaudio.com/forums/showthread.php?s=&postid=1376855#post1376855post1376855
 
Made some small adjustments. However i still do not understand what it is Andrew and Gootee wants me to do..

Can someone make a small sketch to illustrate? or point to a sketch in the datascheet

Thanx all for the help.! :)

This is how it looks now.

[IMGDEAD]http://bildarkiv.hififorum.nu/Zei/SRPS/PS_Schematic_rv2.JPG[/IMGDEAD]


[IMGDEAD]http://bildarkiv.hififorum.nu/Zei/SRPS/PS_overview_rev2.JPG[/IMGDEAD]

Thanx

/Z
 
Hi zei,

I'll see if I can explain this, correctly. I hope that someone will question or correct me, if I say something that is incorrect, or not completely correct, etc.

I think that what AndrewT meant was: On your schematic, from the junction of C9/C10, REMOVE the connection that goes toward the right. Instead, use a new, SEPARATE conductor, from the junction of C9 & C10, that goes all the way to the output Gnd, by itself, without connecting to anything else.

That way, the filter capacitors will not share their ground return currents with the ground connections from R1/R2, C5/C6, or C7/C8.

I am not sure about whether or not C3/C4's ground connection should be included in that, or not.

And you might also want to separate the ground return conductor for C7 and C8 from the conductor used for R1/R2 and C5/C6, although I don't know how important that might be.

The idea is to keep the ground reference voltage, that the regulator uses to sense the load voltages, clean. Ideally, nothing else should share that ground conductor.

If the filter cap's large, dynamic return currents WERE also present, in the conductor between R1/R2/C5/C6 and the output ground, then the regulators' ground references would be less stable ("bouncing" ground voltage), due to the voltages induced across the PCB trace's parasitic resistance and inductance, by the filter caps' relatively large, dynamic return currents.

Does that make sense, to you?

By the way, you might also want to try increasing the values of C7 and C8 to 100 uF.
 
Hi,
c3 & c4 must stay with the regulator, but correct the schematic to show 100nF.
Yes, disconnect the electrolytic smoothing caps from the regulator ground, as Tom says.
Link the smoothing caps direct to the output ground.

It might also help to have separate regulator grounds for each of the regulators so that they don't interfere with each other, when the rail currents are not equal and opposite.

It helps if c5 & c6 are increased, try 100uF.
 
Hi guys.

Thanx very much for helping out.

I think i got it right now, It is however going to mess up my nice symetrical layout i guess..

Is it ok to use a jumper right across the board from Smoothing Caps to output Gnd? :rolleyes:

[IMGDEAD]http://bildarkiv.hififorum.nu/Zei/SRPS/PS_Schematic_rv3.JPG[/IMGDEAD]




zei, your layout is faulty!zei, your layout is faulty!
R 3,4 shouldn't touch ground

This i do not unerstand either.. :xeye: How should they connect?

Thanx

/Z