Not able to raise voltage to assembled components

[ananth]

Hello everyone,
I'm trying to use an LTC3440 buck/boost regulator IC on my PCB board to work with a PIC controller.

A board assembled by someone else works just fine but the one I'm trying to assemble doesn't. I found that the regulator was not giving me the desired output.

Now, I'm just trying to use the regulator in its basic application form given in the datasheet and it still doesn't work inspite of all the components being the same from the previous assembly and the board being the same too. (Do I absolutely need to drive a load with the o/p pin? I've tried with and without to no avail)

I found that I can't raise the voltage input to the board with components beyond 2.3 Volts where I need the input to be at least 2.5 volts for operation. What could be the reason for the voltage not being allowed to rise? The current rises a lot but the voltage doesn't as I try to increase the voltage.

Am I shorting something? Anybody ever have a problem like this?

Any help is appreciated.
Ananth.

 

[VVV]

It's hard to say, without seeing a schematic. However, since the other board works, you clearly have a problem with the layout.
2.3V and an increasing current sounds a lot like the input cap is backwards. Check that, as well as the output cap and make sure they are properly installed.

 

[ananth]

Hello VVV,
Thanks for your input.
I tried the same board in the morning today out of exasperation and it worked! but then it conked off again.. I'll try your suggestions and let you know.
Thanks again.

 

[som_raparty]

hi
i am not sure
but similar problem i faced when i kept floating the o/p gnd
may be something similar
as u r saying the other board works fine, just check up all the components and connections

thnx
som