another jung super regulator pcb layout

[BrianGT]

I made a pcb layout for a jung super regulator*. I am planning on putting the regulators on the analog side of my pcm1792 dac project.

Here are pictures of:
schematic that i used
top layer of pcb
bottom layer of pcb
The footprint of the super regulator is 2" x 1".

As for the use of the super regulator, I figured that since the super regulator will physically be right next to the chip, I tied the sense lines to the output lines. Also, since I already have capacitors on the pcb for decoupling, I removed the 100uF capacitor on the output. Also, the jung regulator, in it's current state will be part of the analog ground plane, with the input from my power supply having the ground seperate from the analog ground plane. (the analog ground plane will be wired seperately back to the central ground).

Are there any issues with my initial implementation? Any improvements that can be done? I tried to keep the wiring as short as possible. Any suggestions/comments/criticisms/ are greatly appreciated.

* The underlying circuit used in this layout is based on the Walt Jung regulator, and primarily based on a modified version by ALW. I claim no intellectual ownership of this design

--
Brian

[peranders]

Looks quite OK but where have you connected AGND to incoming ground?

I don't see any 100nF caps?

[BrianGT]

Originally posted by peranders
Looks quite OK but where have you connected AGND to incoming ground?

I was going to have the analog ground run back to the central ground. This is what ALW did in his schematic. Is this a bad idea?

--
Brian

[peranders]

Originally posted by BrianGT


I was going to have the analog ground run back to the central ground. This is what ALW did in his schematic. Is this a bad idea?

--
Brian

Long loops create inductance (not good) and the possiblity to pick up noise. Yes, not very good idea. Check one more time how Andy has done.

[jan.didden]

Nice layout!

The only thing I would add is a small decoupling cap right across the supply pins of the error amp to avoid supply noise and coupling that could cause ringing or even oscillations.

On the grounding, this is not so simple without knowing the total layout. For example, the agnd from the feedback network and the ref network could be connected together near the amp input, and then connected to central gnd. The current through this lead to central ground can cause unwanted signals, but since they are common to both the reference and the feedback, they will be a common mode input to the errror amp and thus the effect on the final output voltage would be greatly reduced. You really would have to look in this sense to the other wiring as well.

Jan Didden

[Fred Dieckmann]

"I removed the 100uF capacitor on the output."

I wouldn't do that! You have the real potential for an unstable or marginally stable regulator. The circuit is really designed NOT to use high Q (very low ESR) capacitors. The problem is that this regulator is more complicated than it looks. The output capacitor type and location is critical for it to work correctly and sound the best. I am sure that Andy will have some further insight and you may want to email him Brian.

"The only thing I would add is a small decoupling cap right across the supply pins of the error amp to avoid supply noise and coupling that could cause ringing or even oscillations."

Not without some resistive decoupling
of the op amp PS terminal from the regulator output I wouldn't. I believe this was discussed in one of the Jung articles and I will try to find it.

[hegestratos]

Originally posted by BrianGT
I made a pcb layout for a jung super regulator.

Are there any issues with my initial implementation?

From the comment in your schematic I understand that you will connect Vgnd to Agnd somewhere. I'm wondering if you pre-regulator shouldn't have it's Vgnd connected to Vout? That way, the LM317 will put Vprereg approximately 2.5V above Vout, instead of 2.5V above Vgnd. (See ALW's page for details under The Tracking Pre-Regulator.)

Cheers,

Alfred

[Fred Dieckmann]

From the comment in your schematic I understand that you will connect Vgnd to Agnd somewhere. I'm wondering if you pre-regulator shouldn't have it's Vgnd connected to Vout? That way, the LM317 will put Vprereg approximately 2.5V above Vout, instead of 2.5V above Vgnd. (See ALW's page for details under The Tracking Pre-Regulator.)


Ummmm...... How is the regulator going to work with 2.5 volts on the input. Go read
the LM317 datasheet for how to program the output voltage for the LM317.

http://www.national.com/ds.cgi/LM/LM117.pdf

[Elso Kwak]

Originally posted by Fred Dieckmann
From the comment in your schematic I understand that you will connect Vgnd to Agnd somewhere. I'm wondering if you pre-regulator shouldn't have it's Vgnd connected to Vout? That way, the LM317 will put Vprereg approximately 2.5V above Vout, instead of 2.5V above Vgnd. (See ALW's page for details under The Tracking Pre-Regulator.)


Ummmm...... How is the regulator going to work with 2.5 volts on the input. Go read
the LM317 datasheet for how to program the output voltage for the LM317.

http://www.national.com/ds.cgi/LM/LM117.pdf

Hi Fred,
Is this smart youngster with the waving ears a juvenile picture of you???

BTW I found the Jung regulator better sounding without the preregulator, but who am I??
(Just some free advice to confuse the forum members )

[Upupa Epops]

Brian, you must do wider traces in " main current rail ", you get lower output impedance.