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Old 26th January 2006, 03:10 PM   #1
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Default ALW Regulator Current Limit?

I have just tried a fully tested 12V unit to power a dac with a current requirement of 670mA but the unit just shuts down. I can find nonreference in the literature on current limit.

Am I overdrawing current?
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Old 26th January 2006, 04:45 PM   #2
Whit is offline Whit  United States
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Andrew told me a few weeks ago that the current is limited by the preregulator.
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Old 26th January 2006, 05:08 PM   #3
Darry is offline Darry  France
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Between 200 and 500mA
To see : Alwsr rev2.9rev0051.pdf
just above figure 2 ( page10 )

Darry
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Old 26th January 2006, 08:06 PM   #4
Whit is offline Whit  United States
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Look here at post #206.

http://63.99.108.232/forum/showthread.php?p=194356
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Old 26th January 2006, 08:42 PM   #5
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Default Re: ALW Regulator Current Limit?

Quote:
Originally posted by fmak
I have just tried a fully tested 12V unit to power a dac with a current requirement of 670mA but the unit just shuts down. I can find nonreference in the literature on current limit.

Am I overdrawing current?
What is your input voltage?

Do you have cooling, not LM317 or D44H11?

Max current can be calculated backwards.

Hfe 25 min, typ 100 of the D44H11

Current through driver 1V/R1 => 10 mA

That gives max current somewhere between 250-1000 mA but more like the higher value.

The very current limit is set by the LM317, check datasheet for this (1-1.5 A)
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Old 27th January 2006, 04:57 AM   #6
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Default Re: Re: ALW Regulator Current Limit?

What is your input voltage?

------------------------------------------------------------------------------------15-17V
------------------------------------------------------------------------------------

Do you have cooling, not LM317 or D44H11? -YES
------------------------------------------------------------------------------------

Max current can be calculated backwards.

Hfe 25 min, typ 100 of the D44H11

Current through driver 1V/R1 => 10 mA

That gives max current somewhere between 250-1000 mA but more like the higher value.
------------------------------------------------------------------------------------

These values are about right; so why does my regulator shut down at 600mA?


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Old 27th January 2006, 06:09 AM   #7
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Notice at least 250 mA but how much load can it take then?

What does "shut down" mean? A bit voltage drop or what?

Your input voltage with ripple taken into account, min voltage? It must be 15-16 V at least plus ripple.
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Old 27th January 2006, 08:38 AM   #8
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Quote:
Originally posted by peranders
Notice at least 250 mA but how much load can it take then?

What does "shut down" mean? A bit voltage drop or what?

Your input voltage with ripple taken into account, min voltage? It must be 15-16 V at least plus ripple.
------------------------------------------------------------------------------------
My apology; I treated a 15V regulator as though it was 12V; the thing never started even though the LED was on.

Happilly now getting 650 mA on 12 V with 18V input. Now testing geat sink temperature.

My rme dac sounds much better on ALW than LT1085 variable or manufacturer's 'good' switching supply. No hf fixx and more open!.
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