Running one power supply in CV and the other in CC is a perfectly standard way of operating parallel power supplies, so I don't see the problem.
LM317 has a 3 V drop-out voltage
No, no it doesn't.
There are no specifications for operation with less than 3v input to output. A datasheet might give you a plot of
typical drop-out voltages against temperature and current which doesn't tell you how bad performance gets as you approach drop out or what maximums are. I wouldn't design a 317 into anything expecting less than 3v drop out.
LM317 has a 3 V drop-out voltage
No, no it doesn't.
There are no specifications for operation with less than 3v input to output. A datasheet might give you a plot of typical drop-out voltages against temperature and current which doesn't tell you how bad performance gets as you approach drop out or what maximums are. I wouldn't design a 317 into anything expecting less than 3v drop out.
And the 3V figure isn't listed anywhere (the specifications are actually at Vin - Vout = 5V), nor is any fixed dropout voltage. The dropout voltage varies and how close you can get depends on how you're using the regulator.
LM317 has a 3 V drop-out voltage
No, no it doesn't.
2.5 - 2.7 V @ full load (1.5 A) and max. junction temperature. Pretty close to 3 V.
But other specifications in the datasheets are often only specified at a range between 3.0 V <= VI-VO <= 40 V. Sometimes 2.5 V <= VI-VO <= 40 V.
Going under this regulation might get a lot worse than what's specified. Otherwise they would probably specify it down to a lower dropout voltage.
So you can tell what the specifications will be like below 3 V.
The dropout specs varies a bit depending on which manufactures datasheet you look in.
Also note Fairchild specs are only for a junction temperature between 0 and 125 deg C, while ST Micro is between -50 and 150 deg C.
And the 3V figure isn't listed anywhere...
It is at the top of page 3 in TI's LM317 datasheet:
http://www.ti.com/lit/ds/symlink/lm317.pdfRecommended Operating Conditions
VI – VO Input-to-output differential voltage: min. 3 V | max. 40 V
And the 3V figure isn't listed anywhere...
It is at the top of page 3 in TI's LM317 datasheet: http://www.ti.com/lit/ds/symlink/lm317.pdf
Recommended Operating Conditions
VI – VO Input-to-output differential voltage: min. 3 V | max. 40 V
And yet, not the datasheet for the LM317T, which is the TI part I typically use in TO-220.
Can we just agree that rather than blindly following figures which vary wildly between manufacturers, across the same manufacturer, and with the phase of the moon, we should actually design and test things?
And yet, not the datasheet for the LM317T, which is the TI part I typically use in TO-220.
Do you have a link for the TI LM317T datasheet? I can't find it at TI's website.
And yet, not the datasheet for the LM317T, which is the TI part I typically use in TO-220.
Do you have a link for the TI LM317T datasheet? I can't find it at TI's website.
It's under 117.
http://www.ti.com/lit/ds/symlink/lm117.pdfIt does reference 3V for some of the specs, having looked closer, but not in relation to dropout.
Test it and see is the best solution. Or move to a more modern regulator.
Also note Fairchild specs are only for a junction temperature between 0 and 125 deg C, while ST Micro is between -50 and 150 deg C.
They are not specifications they are typical characteristics giving guidance on what may happen if you operate outside the specifications.
Also note Fairchild specs are only for a junction temperature between 0 and 125 deg C, while ST Micro is between -50 and 150 deg C.
They are not specifications they are typical characteristics giving guidance on what may happen if you operate outside the specifications.
Correct. Junction temperature isn't specified to more than 125 deg C even though the curve goes all the way up to 150 deg. C.
And yet, not the datasheet for the LM317T, which is the TI part I typically use in TO-220.
Do you have a link for the TI LM317T datasheet? I can't find it at TI's website.
It's under 117. http://www.ti.com/lit/ds/symlink/lm117.pdf
It does reference 3V for some of the specs, having looked closer, but not in relation to dropout.
Test it and see is the best solution. Or move to a more modern regulator.
I haven't really looked into it, but what's the difference between LM317 and LM317T?
Is it a case of one being a design from the old National Semiconductor and the other being a design from the old TI?
And yet, not the datasheet for the LM317T, which is the TI part I typically use in TO-220.
Do you have a link for the TI LM317T datasheet? I can't find it at TI's website.
It's under 117. http://www.ti.com/lit/ds/symlink/lm117.pdf
It does reference 3V for some of the specs, having looked closer, but not in relation to dropout.
Test it and see is the best solution. Or move to a more modern regulator.
I haven't really looked into it, but what's the difference between LM317 and LM317T?
Is it a case of one being a design from the old National Semiconductor and the other being a design from the old TI?
Your guess is as good as mine. There are a lot of parts like that from TI, few have any difference in specification at all.
I've bought the T/AT because it often seems more readily available than the KCS, so I get a proper tab. I gave up on the lottery of ST parts from most distributers, and my experience with Fairchild has been popped parts and wild variation in specification compared to other manufacturers.
In the LM117 datasheet there's one table for LM117 and another table for LM317A + LM317-N.
I guess LM317-N just a placeholder for all the LM317 versions in the datasheet other than LM317A? E.g. LM317T, LM 317H, LM317K LM317M etc.
In the LM117 datasheet there's one table for LM117 and another table for LM317A + LM317-N.
I guess LM317-N just a placeholder for all the LM317 versions in the datasheet other than LM317A? E.g. LM317T, LM 317H, LM317K LM317M etc.
I believe so. The A is specified down to -40C, the other versions are not.
Can we just agree that rather than blindly following figures which vary wildly between manufacturers, across the same manufacturer, and with the phase of the moon, we should actually design and test things?
Rigol strongly disagrees
But I wouldn't run a part outside it's recommended operating range in a commercial product even if it tests fine there. You never know if it will be the same for the next batch. And you wouldn't be able make any kind of warranty claim against the manufacturer if you run them outside specs.
I know Rigol overclocked 40 MHz ADCs to 100 MHz with great success in the DS1xxxE scopes. They did so because there's 10 ADC in each device and lot of money to be saved for the 40 MHz vs. 100 MHz versions.
But they are from the same die as the 100 MHz parts. Not sure if Rigol tested and sorted each of them before use or if almost all or all of them worked overclocked and they just took the risk.
Bought my DP832 direct from Rigol on Nov 7th. Used it a dozen times or so. Powered it up 2 days ago, Channel 1 failed. Wouldn't source any current. Channel 2 & 3 work just fine. Just the way things go. Either they fail right away or they last for decades, right?
Contacted Rigol this morning (~12 hours ago) via email, explained the issue, etc. Within a few hours, got an RMA and shipping label. Dropped it off for shipping a couple hours ago. I've already got a tracking number for the new unit that's shipping back to me.
:-+You can't beat that kind of service...Can you?
Ok, sure, maybe it could NOT have failed within the first couple of weeks. But other than a handful of minutes packing up the old unit, email'ing, dropping it off, etc., how much am I out?
:-+You can't beat that kind of service...Can you?
Ok, sure, maybe it could NOT have failed within the first couple of weeks. But other than a handful of minutes packing up the old unit, email'ing, dropping it off, etc., how much am I out?
Not if you purchased dozens or hundredths of these that you're going to use in an industrial/commercial usage or worst to be used in your production benches testing lines, imagine how many productivity hours lost because of that.
I think all these DP832 fuss summarized it self pretty well, its suitable only for personal or enthusiast/hobbyist grade usage only, and definitely should be avoided in pro/commercial environment that need a product that just work reliably out of the box when newly bought, not too demanding I guess.
Still nothing for EU owners. I emailed them again, no response.
Who did you e-mail,
http://eu.rigol.com or a European distibutor?
Not if you purchased dozens or hundredths of these that you're going to use in an industrial/commercial usage or worst to be used in your production benches testing lines, imagine how many productivity hours lost because of that.
The same example is valid also for other manufacturers.
Not if you purchased dozens or hundredths of these that you're going to use in an industrial/commercial usage or worst to be used in your production benches testing lines, imagine how many productivity hours lost because of that.
I think all these DP832 fuss summarized it self pretty well, its suitable only for personal or enthusiast/hobbyist grade usage only, and definitely should be avoided in pro/commercial environment that need a product that just work reliably out of the box when newly bought, not too demanding I guess.
Well sure...can't argue that point.
But it wasn't and I'm happy...so...