TPS62142: Problem with output voltage regulation

Emmanuel Santiago Iglesias

Part Number: TPS62142

Hello,

I'm using a TPS62142 in order to provide 3.3V for a TI Lauchpad board and a custom logic board (max. load1.5A) from a 9.9V LiFePO battery. On the power supply board there's also a boost converter with an output voltage of 12V. My problem is that, when i connect the battery (~9.8V) the IC doesn't regulate the 3.3V at the output but ~0.228V. For the design i took as a reference the one given by the webench tool. What could be the problem? Thanks in advance!

Here are the schematic and pcb i'm using and the webench report. 3302.TPS62142_3V3.pdf

over 6 years ago

0 Chris Glaser over 6 years ago

TI__Guru*** 147320 points

Hi Emmanuel,

Is there a load connected to the 3.3V? Can you send waveforms of Vin, Vout, SW, and SS/TR?

0 Emmanuel Santiago Iglesias over 6 years ago in reply to Chris Glaser

Intellectual 280 points

Hi Chris,

thanks for the quick answer and sorry for the delay. Right now i don't have access to an oscilloscope. Tomorrow i can send you the waveforms. There was no load connected when i had an output voltage of 0.228V. I added a 220 Ohm resistor load and the output voltage went up to about 0.6 V.

Regards,
Emmanuel

0 Chris Glaser over 6 years ago in reply to Emmanuel Santiago Iglesias

TI__Guru*** 147320 points

Hi Emmanuel,

Were you able to take some waveforms or maybe even solve this on your own?

0 Emmanuel Santiago Iglesias over 6 years ago in reply to Chris Glaser

Intellectual 280 points

Hi Chris,

sorry for that, today i had access to an oscilloscope. But the waveforms are weird. All i'm getting are DC signals on the pins. Here are the images taken without a load at the output. With load the voltage decreases even further.

Vin:

Vout:

SW:

SS/TR:

0 Chris Glaser over 6 years ago in reply to Emmanuel Santiago Iglesias

TI__Guru*** 147320 points

Yes, this is odd. Was Vin measured across CIN2? Also, change that timescale to something reasonable, like 1 msec.

Do you have other boards or do they all work the same?

Please check your soldering of all components to make sure everything is connected properly with no shorts, etc.

0 Emmanuel Santiago Iglesias over 6 years ago in reply to Chris Glaser

Intellectual 280 points

Hi Chris,

just to let you know, the issue was solved. I rechecked everything, resoldered the component and had the same problem. But at the end it seems to be that the chip was damaged. After ordering new ones and replacing it, everything worked just fine. Thanks for your help!

Regards,
Emmanuel

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TPS62142: Problem with output voltage regulation