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Old 5th November 2003, 08:21 AM   #1
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Question Tl431

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 ...
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Old 5th November 2003, 08:30 AM   #2
dhaen is offline dhaen  Europe
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Check this post:
http://www.diyaudio.com/forums/showt...ht=#post111229
(The attachment is what you need)
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Old 5th November 2003, 08:59 AM   #3
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Default YEEES!

thanx man- you saved my life

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

thanx thanx thanx
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Old 5th November 2003, 09:33 AM   #4
Previously: Kuei Yang Wang
 
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Default 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
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Old 5th November 2003, 10:32 AM   #5
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Default 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
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Old 5th November 2003, 02:06 PM   #6
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Default 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
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Old 6th November 2003, 05:09 AM   #7
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Talking thanx

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 - VEEERY good.
Thanx guys
daniel
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Old 22nd February 2004, 12:31 PM   #8
ABO is offline ABO  Netherlands
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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.
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Old 22nd February 2004, 02:58 PM   #9
Bricolo is offline Bricolo  France
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what is a Pio cap?
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Old 22nd February 2004, 04:34 PM   #10
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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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