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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
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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.
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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
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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)
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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.
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It does, but only 0,05V, so by far not that amount....
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That might suggest that the supply sourcing the Trident is running short of current as well. What input voltage are you using?
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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?
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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.
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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
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To my eyes your setup is perfectly all right.
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