I just received from Digi-Key link http://www.digikey.com/scripts/DkSea...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

 

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!.

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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.

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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?

 

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.

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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).

 

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.

 

Check the number on the chip...We have had a LOT if trouble with Digikey sending the wrong parts.

D.

 

chip says L4931; st 25; yo247

 

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.

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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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