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LD1084 vs LM317 @ 24v
LD1084 vs LM317 @ 24v
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Old 10th January 2020, 01:52 AM   #11
dotneck335 is online now dotneck335  United States
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Join Date: Dec 2012
The LM317 is rated for a maximum of 40 volts of input-output differential---ONLY. There is no 30 volt maximum input as has been suggested. An allowance for a 3 volt dropout is indeed desirable. The LD1084, however, DOES have a 30 volt max input, but offers a 1.3 volt dropout----which could be a critical requirement in some applications.
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Old 10th January 2020, 11:46 AM   #12
MorbidFractal is offline MorbidFractal
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Use the 317 and check the resulting voltages in circuit when actually used in the target application. If the measurements say the 1084 can hack it replace the 317 with the 1084.
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Old 10th January 2020, 03:13 PM   #13
soundwavesteve is offline soundwavesteve  United States
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Thanks for the additional info - I will probably have it powered up this weekend
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Old 10th January 2020, 04:34 PM   #14
keilau is offline keilau  United States
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Join Date: Mar 2013
Location: Windy City, US
Originally Posted by soundwavesteve View Post
I am building the Dual/Biploar LV-Reg power supply from glassware/Tubecad and have two questions. I did email John@glassware a few days ago but I understand of course he might be really busy and hasn't had a chance to reply...I am itching to continue my build

I am confused which regulator to use. The bag the LM317 comes in says use if Raw V is >30. As I am building this supply for 24Vdc, raw input is about 22Vdc. In several places online and in the instructions, he states "If the output voltage is greater than 20Vdc, then the LM317-HV will have to be used as the LDO three-pin regulators present a 30V maximum input voltage". Since this kit is rated for 24V maximum output, input voltage will always be lower than 30V....so why use the LM317? I looked at the spec sheet for the LD1084 and it seems capable of 24Vdc output...the input voltage and output differential are within spec.

I would just use the LM317 and keep building, but he states the LD1084 is a great positive regulator and I am curious why it cannot be used in this application.

I am running the FirstWatt BA-3 as a preamp and I don't know what load it presents, but the article talks only about mA's....

Second question, which you may not be able to answer without seeing the schematic, but R3 is part of a CRC filter but also reveals the current flowing into the load via measuring voltage drop. R3 can be .33, 1, 3.3 or 10 via the provided parts. The instructions state I could use 10ohms if the load is light. What is 'light' exactly? How do I pick which resister to use?
Check out the The LTŪ1083 series from Analogue Device. 30 volts rating up to 7.5 amperes.

Last edited by keilau; 10th January 2020 at 04:39 PM.
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