2.5v Voltage Regulator. Output is only 1v????

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Almazick

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I just received from Digi-Key link https://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=47431&Row=208451&Site=US
2.5V 250ma TO-92 3 pins and I only get 1 volt output from Regulator. I use 4AA batteries. Vin is 5.7v to pin3, ground pin2 and Vout pin1. I tried with 1k and 0.2K load and I still get 1v on Vout pin1. Also I used with and without Capacitors 2.2uf and 0.1uf. What is going on? On chip it says L4931; st 25; yo247. I bought from digikey 10 of these regulators and they are all the same. Please help
 
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Are you absolutely, 100%, definately, positive - you've connected them the right way round?.

No disrespect, but sometimes it's SO easy to get it wrong, it often helps to get someone else to have a look!.
 
Nigel Goodwin said:
Are you absolutely, 100%, definately, positive - you've connected them the right way round?.

No disrespect, but sometimes it's SO easy to get it wrong, it often helps to get someone else to have a look!.
Click to expand...

Yep I'm pretty sure
 
It doesn't figure that all ten would be bad. If you are using a breadboard, reverse the device and see what happens.
 
AllVol said:
It doesn't figure that all ten would be bad. If you are using a breadboard, reverse the device and see what happens.
Click to expand...


Well I just did and reversed regulator. It became very hot as expected. In the first place everything seems to be connected the right way. Anyway the funny thing is that I can't believe that digikey would send me 10 of them and they can be defective and I still can't prove that I'm an idiot and doing something wrong. Any ideas?
 
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Almazick said:
Any ideas?
Click to expand...

Try to eliminate the possibility that the meter is bad.

ST datasheet quoted correct part number for 2.5V as L4931CZ25 or L4931ABZ25 on T0-92 packaging.
 
Very strange Don't remove the output capacitor (2.2 uF, right?) or the LDO regulator may oscillate.
 
You could also try increasing the value of the output capacitor from 2.2uF to at least 10uF (2.2uF is the absolute minimum value on the datasheet).
 
picasm said:
You could also try increasing the value of the output capacitor from 2.2uF to at least 10uF (2.2uF is the absolute minimum value on the datasheet).
Click to expand...


Just took a brand new Regulator from the bag, replaced 2.2uf with 10uf and the same thing. 1V output. aaaaaaaaaaaaaaaaahhhhhhhhhhh. What's going on?????? Well, I'll be calling DigiKey on Monday.
 
Almazick said:
Just took a brand new Regulator from the bag, replaced 2.2uf with 10uf and the same thing. 1V output. aaaaaaaaaaaaaaaaahhhhhhhhhhh. What's going on?????? Well, I'll be calling DigiKey on Monday.
Click to expand...
Check the number on the chip...We have had a LOT if trouble with Digikey sending the wrong parts.

D.
 
It's odd, because they don't make 1.0 volt regulators. The lowest that series goes to is 1.5 volts. Something is definitly wrong someplace.
 
Sceadwian said:
It's odd, because they don't make 1.0 volt regulators. The lowest that series goes to is 1.5 volts. Something is definitly wrong someplace.
Click to expand...


Well, assuming by datasheet the drop voltage is 0.4 it could be 1.5v voltage regulator but on the chip says ST 25. Anyway I'm going nuts because I really need 2.5 voltage regulator for my project. I need to run 7 led display and Pic chip for ADC. I'll be using one power supply for pic chip, led and adc reference
 
Make sure there isn't anything weird with the breadboard - better yet, grab some alligator clips, a 9V battery, and test the part directly.
 
might want to apply some sort of minimal load to the regulator too, maybe it needs to see 1ma or something to go into regulation

if you're set on calling someone, I'd call ST Microelectronics, not Digikey.
 
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