TPS7A47: Change in functionality, stuck at 2.5V and pulls high current

Hey Jeremy,

Can you paste the image? I am unable to download the file.

Also, can you share the full orderable part number?

Thanks, Aaron

Hi Aaron, the full part number is TPS7A4700RGWR.

Hey James,

My apologies - the image is still not appearing. I spoke with my colleague and was told you need to first save the image and then insert it with the 'Insert/Edit Media' button.

Sorry for the inconvenience.

~ Aaron 

Hey Jeremy,

The schematics look good to me. Are you seeing the LDOs sourcing current even without a load connected to the output? 

If so, you may want to look into the possibility of a short. These packages can be tricky to solder. I usually apply a heat gun to make sure the solder underneath is not extending beyond the pad. 

~ Aaron

Thanks Aaron. I agree these are tricky to solder by hand. In this case, we had the boards assembled by the PCB house. I'm also pretty sure this isn't due to a short - in addition to the continuity and isolation measurements looking as expected, we are seeing this same issue on both LDOs per board over all 5 boards. I was thinking maybe it was a bad batch of parts and others may be having similar problems. 

Another thing I plan to try is adding a diode to protect against reverse current. I do have a decent amount of capacitance on the outputs that could allow for current to flow back through the part. However, I built 12 of these exact same boards a year ago and everything worked as expected.

Hey Jeremy,

If we rule out a short then the reverse current scenario is definitely worth checking out. Are there situations where VOUT is biased higher than VIN? 

I'll check the return history on this part but I don't think we've had anything of this nature. 

~ Aaron