7815 and 7915, which type A or C? - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th December 2010, 11:43 PM   #11
diyAudio Member
 
Join Date: Oct 2006
The 10uF caps are after the big 6800uF filter caps but before the regulators, so maybe they are part of some bypass for the big filter caps.
The design is mur860's into 6800uF the into 10uF caps and the into 7815 and 7915, then out to 10uF, the to 47uF then to op-amp power rails. (btw this is on Behringer Truth B2031 powered monitors,with LM3886 amps)

out,
Robert
  Reply With Quote
Old 14th December 2010, 08:56 AM   #12
diyAudio Member
 
Join Date: Sep 2010
Location: Melbourne
Quote:
Originally Posted by nigelwright7557 View Post
The datasheet says you dont need a decoupling capacitor on the output.
Maybe so, but a board full of TTL with a 2 MHz clock and 10 ns rise times is not something I would hang off a slow regulator with no decoupling. The other advantage is the decoupling acts as a low pass filter reducing regulator noise.
  Reply With Quote
Old 15th December 2010, 12:50 AM   #13
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
I wouldn't base a design on spec. sheets that differ in age by maybe 30 years. Test methods change with time. Chip manufacturing processes change with time.
__________________
Kevin
  Reply With Quote
Old 15th December 2010, 08:21 PM   #14
diyAudio Member
 
Join Date: Oct 2006
Quote:
Originally Posted by Speedskater View Post
I wouldn't base a design on spec. sheets that differ in age by maybe 30 years. Test methods change with time. Chip manufacturing processes change with time.
Hello,

Is this referring to what I posted?

Thank You,

Robert
  Reply With Quote
Old 16th December 2010, 06:36 PM   #15
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
Quote:
Originally Posted by rfenergy View Post
Hello,
Is this referring to what I posted?
Thank You,
Robert
Yes, I think that you are putting too much faith in spec. sheets. Manufacturing techniques change with time, mfg. seldom update the spec. sheets.
__________________
Kevin
  Reply With Quote
Old 16th December 2010, 07:23 PM   #16
diyAudio Member
 
Join Date: Oct 2006
I get what you are saying.

The newer parts are probably an improvement, but the sheets do not reflect this fact.

out,
Robert
  Reply With Quote
Old 17th December 2010, 05:10 PM   #17
jitter is offline jitter  Netherlands
diyAudio Member
 
jitter's Avatar
 
Join Date: Aug 2004
Location: Eindhoven, The Netherlands
Quote:
Originally Posted by Speedskater View Post
Yes, I think that you are putting too much faith in spec. sheets. Manufacturing techniques change with time, mfg. seldom update the spec. sheets.
I wouldn't be too sure of that. Recently I downloaded some datasheets fom ST and others of some very standard components (78xx, LM317, etc). to answer a question in another thread (My Transistors, original or copy?) and actually found them to be very up to date. All of them had a revision date in 2010.
These were downloaded directly from the manufacturers and not at third party, though...
  Reply With Quote
Old 17th December 2010, 06:18 PM   #18
diyAudio Member
 
Join Date: Oct 2006
Jitter,

it looks like you are correct, I found new spec sheets at On-Semi. The newer 78XX and 79XX have different specs (and generally better) than some older spec sheets I found on the internet.

The newer 7915 form On-Semi has better specs than the older ones.

I guess the question I still have is the On-Semi NCP7815TG with 6.8uV/VO output noise voltage and 70db of ripple rejection better than the old LM7815A I have in there? The LM7815A is over 10 years old, the newer spec sheet I found on the LM7815A has a better noise spec of 90uV. but I do not know if this is the total noise or if it is measured in uV/VO.

Thank You,
Robert
  Reply With Quote
Old 18th December 2010, 06:54 AM   #19
jitter is offline jitter  Netherlands
diyAudio Member
 
jitter's Avatar
 
Join Date: Aug 2004
Location: Eindhoven, The Netherlands
The units tell you if it's total noise or noise per volt output.
total noise = uV
noise per volt output = uV/VO.
If the manufacturer used the units correctly, that means that 90 uV is total noise.

A bit of mathematics shows this is most likely true:
6.8 uV/VO * 15 VO = 102 uV (total noise for the NCP7815TG)
90 uV/15 VO = 6 uV/VO (noise per volt output for the LM7815A)

Last edited by jitter; 18th December 2010 at 06:59 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
7815/7915 dual supply hum problem Lenn Art Power Supplies 8 22nd March 2011 09:57 PM
Pin compatible 7815/7915 replacements? i-s Parts 9 26th October 2010 04:05 PM
7805 with adjR vs 7815 wleediy Power Supplies 0 30th March 2008 11:18 PM
7815 lopan Parts 4 14th November 2004 02:19 AM
7815 not regulating. JoeBob Solid State 16 8th September 2003 12:51 PM


New To Site? Need Help?

All times are GMT. The time now is 11:42 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2