• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 63 subscribers
  • Views 848 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS61200 VAUX supplied from VOUT?

Markus Schneider58
Prodigy 30 points
Other Parts Discussed in Thread: TPS61200

Hi,

I'm using the TPS61200-EVM with a solar module(3W, max 5V) as source and a 35F / 2.7V Supercap as output.

UVLO-Divider is set to 3V switch on.

At low light condition the device stucks with a VIN-voltage of .25V. But VAUX remains at 1-1.8V.

Even when I remove the solar module VAUX is still at this level.

Is VAUX supplied from Supercap through VOUT-pin?

Should the UVLO setting prevent the IC to stuck at such low input voltage?

When I connect the solar module directly to VIN , "behind" the 100Ohm resistor, the device tends not to stuck. What is the reason?

Thanks for help, best regards

  • 0
    TI__Intellectual 2270 points
    Hi markus

    VAUX is from the max(VIN VOUT), If Vin is too low whle Vout is still there VAUX can also hold the value. UVLO setting can't avoid the the situation you described, because in such a low VIN and VAUX, the whole device is no longer in normal operation, it's no longer in "shudown" state unless the VAUX is higher than 2.4V.

    what do you mean "behind" a 100 ohm resistor, can you post the schematic(both behind 100 ohm and before 100 ohm)

    Charles
  • 0 in reply to Charles Wong1
    Prodigy 30 points

    Thanks for your answer. That VAUX is supplied by VOUT is not mentioned in datasheet I think.

    The problem is that VAUX regulator soaks all the power from the supercap until it is empty. I measured ~330µA at 2.6V towards Pin VOUT.

    I tried to solve this with a schottky diode between 2x10uF caps and the supercap at J3.

    With behind 100 Ohm I meant the point between R1 and VIN-pin (red square). When I connect the solar module there

    doesn't stuck.

    Do you have any hint for me?

  • 0 in reply to Markus Schneider58
    TI__Intellectual 2270 points

    markus

    1.the block diagram has shiwn VAUX is form VIN or VOUT.

    2. what do you mean after "100 ohm resistor, not stuck"? what's the value of VIN and VAUX,Vout this time?

    3.you mean the UVLO is setted to 3V? but the supercap is only 2.7V, what's the output voltage?

    4.

    4. so from your application, you want to block the path from supercap to the chip, even VIN is very low, right? under such condition, VAUX will decrease below 2.4V and the chip will not work normally.

  • 0 in reply to Markus Schneider58
    TI__Intellectual 2270 points
    Hi

    If the problem has been solved, please close the thread;if not, I'm glad to provide further support.

    Charles
  • 0 in reply to Charles Wong1
    Prodigy 30 points
    Hi, is there any option to prevent VAUX is powered by VOUT?
    I assume only way is to disable tps61200 by EN=Low?
  • 0 in reply to Markus Schneider58
    TI__Guru**** 191445 points

    Per the datasheet, VOUT is internally connected to the VAUX regulator.  You could either disable the device, or possibly add a disconnect switch to your storage capacitor.