TL 431 regulator question

[JC951t]

Hi All,
Need some advice. Aside from low noise, how does the
TL431 sound with pre- regulation when used in a dac ?
Sorry, I know this is subjective but would like to hear
your opinions especially when applied to the TDA1541a
dac.

Thanks to all

 

[philpoole]

Well, my first 1541 DAC used single, 78xx based regulation, and it didn't sound as good as my second DAC, dual regulated lm3x7 followed by TL431.
There may well be better out there, and I haven't measured performance, but it does work well.

 

[JC951t]

Hi,


Thanks for sharing your experience

 

[AndrewT]

Hi,
the TL431 is a shunt regulator.
What limits the shunt current if the preceding regulator is a series type?

 

[philpoole]

Hi AndrewT,

If I understand the question correctly, I use a resistance to limit the current before the TL431. I think I use about 100R. Seems to work okay.

Is that what you mean?
Cheers,
Phil

 

[AndrewT]

I use a resistance to limit the current before the TL431. I think I use about 100R. Seems to work okay.

Is that what you mean?

yes, a resistor will do just fine.
Alternatively, set up the LM317 as a current source to replace both the pre-regulator and the resistor.

 

[philpoole]

Unfortunately, the pre-regulator feeds other circuits, so using it as a current source isn't really an option.

Is the 317 a good current source?

 

[JC951t]

Hi Philpoole,

Actually I'm toying with that idea but using LT1085
& LT1033 as current source to power the 24 TL431.
Planning to built EC Design DI8M dac.

 

[martin clark]

Is the 317 a good current source?

Actually it appears, really quite good: and if you cascode two, they perform superbly well. See for yourself in Walt Jung's two 'Sources 101' papers on current-sources here:

http://waltjung.org/Late_Articles.html

As usual, excellent reading!

 

[ridwans]

ask to calculate r Value

Hallo.
i want to ask anyone whose know
how to calculate R
(R1,R2,R3 /R1A,R2A,R2B) value of combination Reg LM317/337 and TL 341

i plant to use for reg +15 -15 output current 300Ma.
input volate +- 20V dc
output 15V
output current 300Ma
this the schematic.

please heelp anyone.
thx

 

[AndrewT]

Re: ask to calculate r Value

how to calculate R
(R1,R2,R3 /R1A,R2A,R2B) value of combination Reg LM317/337 and TL 341

Hi,
first download the datasheets for the 317 and 431.
Set the 317 (CCS) to ~= Iload + Ishunt.
Then calculate according to the datasheets.