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TLV70233DBVR Stops regulating

user4721001
Prodigy 40 points

Hi there,

We are using the TLV70233DBVR with +5V in the input. We have two 1uF/6V3 X7R, one on the input and other on the output. The load capacitance at the output is composed by a 10uF/100nF/10nF/1nF in parallel.

What we are experiencing is that at startup the regulator works ok, regulating the output for 3V3, after a few seconds(1~2) it ramps up to +5v, after some seconds it starts to regulate again, and it keeps doing this over and over.

We have some other product that is using this regulator with exactly the same load and no issues are seen.

We suspected gnd coupling issues so we improved the ground plane of the chip, even so the problem persists.

Can anyone help in any way? 

I tried 100nF in the input and 1uF/X7r in the output, both 1uF, the issue presists....

Thanks!

  • 0
    TI__Intellectual 960 points
    Hi,

    With the information you provided, it looks to me like you have a other part on the 3V3 rail, which is causing a leakage. Since we do not have LDO, which can sink voltage from the output, that would explain why it's only regulating at 3V3.

    Are you powering any other device with the 3V3 rail, which is also connected to a 5V rail or higher?

    Best regards,
    Nicolás
  • 0 in reply to Nicolás Román
    Prodigy 40 points

    Hi Nicolás,

    "... other part on the 3V3 rail, which is causing a leakage"

    No, we just have on Chip with the load capacitance I described.

    "Are you powering any other device with the 3V3 rail, which is also connected to a 5V rail or higher?" 

    Also no. It's a SPI device that is supplied by the TLV70233. The SPI lines work at +5V. But as said, we have another product with the same schematic. regulator and chip to supply, that has the same SPI lines at +5V and everything works ok.

    Also, I removed all components from the 3V3 line, left just the regulator with the two 1uF caps, and the problem persists. It regulates to the 3V3 as it should, then ramps up to the 5V, then goes down again to the 3V3, for eternity. (so I think we can exclude load problems on the 3V3 line).

    Hammering the thing with a 3V3 zener on the output, we can catch this ramp up and avoid it, but don't know if is messing with the TI chip on the long run.

    I looked again at the PCB, and the gnd goes directly to the gnd source, so I also doubt PCB design faults. I'm running out f ideas.....

    Thanks for the reply!!!

  • 0 in reply to user4721001
    TI__Intellectual 960 points

    Hi,

    well to narrow down the problem I would suggest to perform a AB BA swap. Specially since you have an other board with the same power rail which is working. (AB BA swap = take the working LDO of the working board and swap it with the LDO witch is causing problems on the board which is causing problems) I would be interested if the 5V issue keeps happening on the same board or if it occurrence now on the board which was performing well.

    I also suggest to clean the board after soldering, since flux residues are a known cause for voltage leakage.

    Best regards,
    Nicolás