Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Options
View
Go to last post Go to first unread
Florianderton  
#1 Posted : Tuesday, July 23, 2013 2:48:18 PM(UTC)
Florianderton

Rank: Member

Groups: Member
Joined: 7/8/2013(UTC)
Posts: 43
Austria
Location: Bad Ischl

Hello,

hope somebody can help me. I am building my Buffalo DAC, and I need a 3,3V supply for my clock for the I²S source. So I have bought an extra Trident 3,3V. It's perfect 3,297V, but as soon I attach it to the load (= clock oscillator board, roughly 30mA) the voltage drops down to 2,1V and it doesnt work any more.

R4 is 20 Ohms. Can I change this resistor in order to get more CCS current? Or what do you think is the problem?

Thanks for your help!

Florian



avr300  
#2 Posted : Tuesday, July 23, 2013 7:23:58 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
Brian Donegan  
#3 Posted : Tuesday, July 23, 2013 8:33:58 PM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,784
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 126 time(s) in 121 post(s)
10R would be a better value. You can solder a TH 20R in parallel with the SMD 20R. Another option would be to solder a small trimmer to the TH pads and adjust as needed.
Florianderton  
#4 Posted : Tuesday, July 23, 2013 9:07:42 PM(UTC)
Florianderton

Rank: Member

Groups: Member
Joined: 7/8/2013(UTC)
Posts: 43
Austria
Location: Bad Ischl

Thank you, I have already known this document. I have tried now the following:

I decreased R4 from 20,4 to 15Ohms - but still only 2,4V output under load. I have measured again, I need only 36mA. So plus 20mA shunt current would give roughly 60mA CCS current - not too much.

I noticed something: across R4 I measure 1,31V - that is not in between the described range from 1,35V - 1,4V. - So do I have to change something else perhaps?

Thank you,

Florian
Florianderton  
#5 Posted : Tuesday, July 23, 2013 9:19:35 PM(UTC)
Florianderton

Rank: Member

Groups: Member
Joined: 7/8/2013(UTC)
Posts: 43
Austria
Location: Bad Ischl

Thanks Brian,

I have tried now 9 Ohms, and it's working now. But, there is still a voltage drop from 3,289 without load to 3,265 with load now. Is that normal and okay? Or does this still mean my oscillator suffers from a shortage of current supply? May I try less than 9 Ohms (as described in the pdf)? As my voltage across R4 is only 1,31V?

Thank you

Edited by user Tuesday, July 23, 2013 9:23:23 PM(UTC)  | Reason: Not specified

avr300  
#6 Posted : Wednesday, July 24, 2013 7:37:39 AM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
Have you measures the input voltage to the trident. Is that also dropping (that tiny fraction) ?

I would say that such amount of drop is insignificant. If it works, you're fine.
Florianderton  
#7 Posted : Wednesday, July 24, 2013 7:53:01 AM(UTC)
Florianderton

Rank: Member

Groups: Member
Joined: 7/8/2013(UTC)
Posts: 43
Austria
Location: Bad Ischl

It does, but only 0,05V, so by far not that amount....
Brian Donegan  
#8 Posted : Wednesday, July 24, 2013 6:19:29 PM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,784
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 126 time(s) in 121 post(s)
That might suggest that the supply sourcing the Trident is running short of current as well. What input voltage are you using?
Florianderton  
#9 Posted : Wednesday, July 24, 2013 8:10:20 PM(UTC)
Florianderton

Rank: Member

Groups: Member
Joined: 7/8/2013(UTC)
Posts: 43
Austria
Location: Bad Ischl

I use a Placid HD as source, CCS current = 630mA with bigger heat sinks, this Placid is also source for the Buffalo DAC IIISE. - Should be enough, isnt it? Voltage of Placid HD is 5,11V when warm. - Good?
avr300  
#10 Posted : Saturday, July 27, 2013 3:44:47 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
Sorry, I can't follow you.

Quote:
But, there is still a voltage drop from 3,289 without load to 3,265 with load now


That's 0.024v

and

Quote:
It does, but only 0,05V, so by far not that amount....


I might have missed the whole point - if so bare with me.
Florianderton  
#11 Posted : Saturday, July 27, 2013 5:05:45 PM(UTC)
Florianderton

Rank: Member

Groups: Member
Joined: 7/8/2013(UTC)
Posts: 43
Austria
Location: Bad Ischl

Thanks avr300 for your answer.

Sorry, perhaps I have described it a bit confusing. - My Placid HD is dropping 0,05V. And the Trident still 0,024V. - Is that normal and can be left like this? I am pretty green about this all, but I dont want to get worse performance, just because I am unable to set my supplies properly.... I mean, does a voltage drop mean less performance?

I made this calculations:

440mA is needed for the Buffalo IIISE + 50mA shunt = 490mA
36mA is needed for the clockboard + 20mA shunt = 60mA

-> 550mA

I have actually set 630mA CCS current at the Placid! - So where is the problem.... 5,11V to little? Or is such a voltage drop normal?

Thanks for your opinion/ help!

Florian
avr300  
#12 Posted : Saturday, July 27, 2013 5:59:45 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
To my eyes your setup is perfectly all right.
Florianderton  
#13 Posted : Saturday, July 27, 2013 6:08:31 PM(UTC)
Florianderton

Rank: Member

Groups: Member
Joined: 7/8/2013(UTC)
Posts: 43
Austria
Location: Bad Ischl

Okay, thanks! )
Rss Feed  Atom Feed
Users browsing this topic
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.