voltage problem in my PCB

[fallingrain_83]

Hi all friends
I do not know if here is the right place to post this I do apologize in advance
I designed a PCB board that has 2 A/Ds, 1 Microcontroller, 1 FPGA chip, and other elements the problem is with the voltage supply
I have a regulator that converts 5 volt to 3.3 and this voltage supplies other elements of my circuit. as I plug my populated PCB board I have just 3 volts over my board (instead of 3.3v) however the output of my regulator is 3.3 and it warms up and two A/Ds get some how warm too but not that much.
I have a bare PCB board which is not populated and I tried to populate just the power supply part (regulator with related resistors and capacitors) and plug it to see if I have 3.3 over the bare board. the answer is yes I have a nice and clean 3.3 over my bare board.
the other thing that I considered was the resistance between my 5 volt and GND which was 4.5kohm and I think that is normal and the load of my circuit is ok too.
I do not know where to start checking my board and if I plug it for short time to check voltages and all that may it hurts components on my circuit?
I do not know how to search for this problem to find similar situation and solution.:|
I need some suggestions regarding this problem
I appreciate your help and response
let me know if you need more information to help me

 

[IanP]

“I have just 3 volts over my board (instead of 3.3v) however the output of my regulator is 3.3 and it warms up”

It looks like the track that you use as the 3.3V rail is to thin and (working as a low-ohm resistor) causes the voltage to drop from 3.3V to 3.0V ..

Linear regulators can be warm as they dissipate power, in your case (from 5V to 3.3V) * current ..
Maybe this regulator is undersized (comparing with the “appetite” of these 2 A/Ds) and just starts going into current-limit mode, or there is no ceramic cap in the vicinity of the regulator and it starts to oscillate, or .. and or .. and or ..

Rgds,
IanP

 

[karesz]

Yea_all are possible, but tell us some more details pls!
2 ADCs can mean only i.e. 30mW, FPGA canbe other 30/ but 400mW too & the uP the same.
Other question is Dynamic?, maybe you have the over current as static system yet?
Are the polarized capacitors right populated, or some IC maybe rotated!?
Are your solderings all ok?
To end, as IanP wrote too_how big is your regulator dimensioned, has these enough capacity & cooling too?
K.

 

[rajudp]

took like some current related problem,

 

[cameo_2007]

you said you assembled just the power supply part alone and it worked fine.

now start assmebling the other circutry one by one.
First the microcontroller, then the ADC 1 ,2,other chips and not necessary in that order.

you should be getting a more clear picture of which section is creating the problem.

 

[wowo1215]

The first thing I can suggest is you must post some related information, like the schematic and layout, then you can get some useful analysis soon.
Another thing you can do is what cameo_2007 said. or just do the opposite like i usually did.