Post by thread:[EE]: Voltage Regulator Trouble

I have had trouble figuring out the problem with a 5V voltage regulator circuit I am building. I soldered it together and at first it didn't work. I realized it was a soldering error on my part and there was a short. I got it working and didn't think any thing of it. The next day I test it to find that it is not working properly. There is a very small voltage on the output of the regulator that quickly drops to 0 when I test it. Suspecting another short I use a continuity test and find nothing. I test it many times with no results. Then out of nowhere it starts working again. This has got me baffled. I am wondering if it could be a fault with the regulator itself. I am sure that none of the other circuitry and ICs are to blame. Perhaps the regulator got to hot during soldering even though I used a heat sink. Here is the regulator circuit: _______ | | Vin ---+-------+----| IC1 |----+------- Vout | | |_______| | | | | | --- --- | --- C1--- C2--- | --- C3 | | | | +-------+--------|--------+ Gnd C1 - 100uF electrolytic cap C2, C3 - 0.1uF tantalum IC1 - L4940V5 low drop out voltage regulator The drop out voltage of the regulator is 0.5V. Any ideas on what the problem is? Thanks -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Sorry, for some reason the schematic is totally messed up. -----Original Message----- From: pic microcontroller discussion list [spam_OUTPICLISTTakeThisOuTMITVMA.MIT.EDU]On Behalf Of Richard Mellina Sent: Tuesday, July 23, 2002 1:42 PM To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU Subject: [EE]: Voltage Regulator Trouble I have had trouble figuring out the problem with a 5V voltage regulator circuit I am building. I soldered it together and at first it didn't work. I realized it was a soldering error on my part and there was a short. I got it working and didn't think any thing of it. The next day I test it to find that it is not working properly. There is a very small voltage on the output of the regulator that quickly drops to 0 when I test it. Suspecting another short I use a continuity test and find nothing. I test it many times with no results. Then out of nowhere it starts working again. This has got me baffled. I am wondering if it could be a fault with the regulator itself. I am sure that none of the other circuitry and ICs are to blame. Perhaps the regulator got to hot during soldering even though I used a heat sink. Here is the regulator circuit: _______ | | Vin ---+-------+----| IC1 |----+------- Vout | | |_______| | | | | | --- --- | --- C1--- C2--- | --- C3 | | | | +-------+--------|--------+ Gnd C1 - 100uF electrolytic cap C2, C3 - 0.1uF tantalum IC1 - L4940V5 low drop out voltage regulator The drop out voltage of the regulator is 0.5V. Any ideas on what the problem is? Thanks -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.