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Help choosing +15V reg: L7815CV or LM340T-15?

P

PeterD

Jan 1, 1970
0
Which do you think is the better +15V reg:

ST MicroElectronics L7815CV ... http://www.st.com/stonline/products/literature/ds/2143/l7815c.pdf
or
National Semiconductor LM340T-15 ... http://cache.national.com/ds/LM/LM340.pdf

Comparing their datasheets, it seems to me that the ST L7815CV is
slightly superior, but I'm not really sure as I'm not an expert at
reading datasheets. :) Could someone please help me verify this?

Thanks a lot! :)

Define 'better'...

Describe your application and its parameters...
 
Define 'better'...

Describe your application and its parameters...

Better would be more stable and clean output voltage under, say, 20%
to 50% load conditions. This reg is for the analog supply to the
opamps of a Delta 1010 soundcard/audio interface which has 8 analog
inputs A/D, 8 analog outputs D/A, 1 S/PDIF stereo input, and 1 S/PDIF
stereo output. The input voltage to the reg is 23V with a ripple of
about 1.2V. Thanks.
 
E

ehsjr

Jan 1, 1970
0
Better would be more stable and clean output voltage under, say, 20%
to 50% load conditions. This reg is for the analog supply to the
opamps of a Delta 1010 soundcard/audio interface which has 8 analog
inputs A/D, 8 analog outputs D/A, 1 S/PDIF stereo input, and 1 S/PDIF
stereo output. The input voltage to the reg is 23V with a ripple of
about 1.2V. Thanks.

The 340 has better line & load regulation shown on the
datasheet than the 7815. For load: The 340 shows 35 mV,
5mA to 1.5A. The 7815 datasheet shows 150 mV for the same
range. For line: the 340 shows 22 mV, the 7815 shows 150 mV

It may be that "better" as you defined it does not matter
in your circuit.

Ed
 
The 340 has better line & load regulation shown on the
datasheet than the 7815. For load:  The 340 shows 35 mV,
5mA to 1.5A. The 7815 datasheet shows 150 mV for the same
range. For line: the 340 shows 22 mV, the 7815 shows 150 mV

It may be that "better" as you defined it does not matter
in your circuit.

Ed

I think you are comparing the LM340A. This is what confuses me about
the datasheet. On the ordering info page, it lists the LM340A as
available only for 5V. However, on the LM340A electrical
characteristics (page 4) you can also see 12V and 15V. I did some
searching on National's site and Newark, and it looks like the 12V and
15V of the LM340A are no longer in production. Only the LM340 without
"A" is available for 12V and 15V. Therefore, the plain LM340 is what
I would like to compare. Looking at the LM340 electrical
characteristics on page 5 of the datasheet, it seems that the LM340
has inferior specs compared to the LM340A. Compared to the L7815, the
LM340 has slightly inferior output noise voltage and ripple rejection
specs. Based on this, I would like to confirm if you also think that
the L7815 is superior, however slightly, to the LM340. Thanks.
 
F

Fred Bloggs

Jan 1, 1970
0
I think you are comparing the LM340A. This is what confuses me about
the datasheet. On the ordering info page, it lists the LM340A as
available only for 5V. However, on the LM340A electrical
characteristics (page 4) you can also see 12V and 15V. I did some
searching on National's site and Newark, and it looks like the 12V and
15V of the LM340A are no longer in production. Only the LM340 without
"A" is available for 12V and 15V. Therefore, the plain LM340 is what
I would like to compare. Looking at the LM340 electrical
characteristics on page 5 of the datasheet, it seems that the LM340
has inferior specs compared to the LM340A. Compared to the L7815, the
LM340 has slightly inferior output noise voltage and ripple rejection
specs. Based on this, I would like to confirm if you also think that
the L7815 is superior, however slightly, to the LM340. Thanks.

Why don't you get a sample of both and compare their performance in the
actual circuit...I hope you have advanced measurement methodology
experience.
 
R

ram27

Jan 1, 1970
0
E

Eeyore

Jan 1, 1970
0
Better would be more stable and clean output voltage under, say, 20%
to 50% load conditions. This reg is for the analog supply to the
opamps of a Delta 1010 soundcard/audio interface which has 8 analog
inputs A/D, 8 analog outputs D/A, 1 S/PDIF stereo input, and 1 S/PDIF
stereo output. The input voltage to the reg is 23V with a ripple of
about 1.2V. Thanks.

Use an LM317. You can decouple the sense input ( 10uF cap with 220R in
series from sense to GND) which helps reduce ripple, although I bet that
won't matter much anyway to your circuitry, but it'll keep you happy
perhaps.

Graham
 
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