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sparkle 5th November 2003 08:21 AM

Tl431
 
2 Attachment(s)
hello guys!

i have a questino. few days ago I made TDA1543/CS8412 DAC. Powe supply on my DAC (TDA chip) is like in picture. I tought that I would be able to set the voltage on my TDA but it is not working. Only if I chenge the 82R the voltage is going up or down. Is this o.k. or I made it wrong?
Maybe it is stupid question but ...:bawling:

dhaen 5th November 2003 08:30 AM

Check this post:
http://www.diyaudio.com/forums/showt...ht=#post111229
(The attachment is what you need) ;)

sparkle 5th November 2003 08:59 AM

YEEES!
 
thanx man- you saved my life:D :D :D :D :D :clown:

please tell me what is Idiv/Iref what value should I use there

thanx thanx thanx:D

ThorstenL 5th November 2003 09:33 AM

Re: Tl431
 
Konnichiwa,

Quote:

Originally posted by sparkle

few days ago I made TDA1543/CS8412 DAC. Powe supply on my DAC (TDA chip) is like in picture. I tought that I would be able to set the voltage on my TDA but it is not working. Only if I chenge the 82R the voltage is going up or down. Is this o.k. or I made it wrong?

You made a fundamental mistake.

The TDA1543 draws around 60 - 80mA Per chip @ 5V, more at higher voltages. If you are dropping 5V across your series resistor and you have 120mA Flowing (60mA in the DAC & 60mA in Shunt) you resistor needs to be around 39R, not 82R. For 6.66V & 160mA the series resistor should be around 22R.

Also, you might consider changing the 100nF Capacitor to a 22uF or larger value one (recommended Sanyo Os-Con SH Series) and to connect it directly to the Pot's wiper. The load capacitor should also be Os-Con SH 22uF.

Sayonara

sparkle 5th November 2003 10:32 AM

mr wang
 
thanx I see it now- i guess i need that;)

I have tought before to connect that 100nF cap to pot's wiper but also tought that larger value would be to high. i will try to put 22uF. my output cap (one with no value on the picture) is 22uF ELNA.
I tought that my TL431 is not working right because the sound was not good.

thanx guys:)

ThorstenL 5th November 2003 02:06 PM

Re: mr wang
 
Konnichiwa,

Quote:

Originally posted by sparkle

I have tought before to connect that 100nF cap to pot's wiper but also tought that larger value would be to high.

No, you need a value large enough to "couple" the AC signal on the rail into a 1K impedance. Now 22uF/1k is equivalent to a 7Hz -3db point or a rise of the dynamic impedance to around 1.414 the value per datasheet compared to higher frequencies.


Quote:

Originally posted by sparkle

my output cap (one with no value on the picture) is 22uF ELNA.

Make sure it has an ESR of around 0.15R and is well bypassed. I prefer Sanyo Os Con SH Series over most other Cap's simply because more like a capacitor at high frequencies than most other elcap's.

Quote:

Originally posted by sparkle

I tought that my TL431 is not working right because the sound was not good.

It is not working. There is no current left for it to work with....

Sayonara

sparkle 6th November 2003 05:09 AM

thanx
 
2 Attachment(s)
Dear mr. Wang- thanx
You were very helpful. I connected everything like in the picture. I will turn resistor 56R (I am working on 6,0V output voltage now) further down and connect 22uF capacitor on the 100nF. Only 100nF would be connected like You said ( pot's wiper and resistor)- I have no time yesterday to do more changes - but the good news is that TL431 is working allready and I can hear it to. After I did that I put an Riken resistors on I/V an ref. and tantal resistor on output to gnd. Also I have 0,1uF russian silver PiO in parralel with 4,4uF MKP from Rifa. It is working like :bigeyes: - VEEERY good.
Thanx guys
daniel

ABO 22nd February 2004 12:31 PM

If you look at the datasheet for TL431 you'll find that the device has a pole at 8 kHz. It makes sense to compensate for this pole by creating a zero in the feedback on that same frequency. This is done by the 100 nF cap. If the zero is at too low a frequency the feedbackloop may become less stable and show some ringing on transients.

In this case I would use a 15-18 nF cap. Combined with the 1200 ohm feedback resistor puts the zero in the right place.

Bricolo 22nd February 2004 02:58 PM

what is a Pio cap? :confused:

sparkle 22nd February 2004 04:34 PM

bricolo
maybe "paper in oil" ;)

ABO
could You post some sch.. please
thanks (I don't get what You have in mind with 1200 ohm resistor)
daniel


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