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ptn78060wad

Karina Espejo
Prodigy 40 points

Hi,

I placed 2 trimmer in order to regulate the output voltage of the PTN78060WAD. Both trimmer are 10% 100ppm with values 10e5 and 1e3. I supposed this may cause variation at the output and for a 5.5V, I think I should have around 14mV variation for 10°C variation of temperature. However, when I measure I got 200mV for 10°C variation in temperature (20°C-30°C). That is a huge variation for my application. Do you think that these trimmers may cause this variation?

As an aditional comment voltage output is connected through a voltage divider to a microcontroller in order to measure the voltage via software. But at the beginning the microcontroller is not programmed. Would this be a reason of the voltage output variation? Because when I just set the microcontroller in Reset mode, the output voltage variation from the PTN8060AWD is more stable but there is still a voltage output variation of 40mV for 10°C variation. I dont know if you have experienced this before.

Then something that I also observed is that when Rset is mounted, its value is changed. Is there a parallel resitance between the Adjust pin and GND?

Kind regards,

Karina

  • 0
    TI__Mastermind 38230 points

    Karina:

    Trimmers have a poor thermal tolerance will easily drift with temperature.

    Any mV change in voltage applied to the Rset Adjust pin will immendately affect its output voltage.

    For example, if the Rset voltage varies by 30mV, then the output will vary by 250mV.

    There is an intenral 54.9kΩ resistor to ground.

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 40 points

    Hi Tom,

    According to Trimmer data sheet, they are 100ppm. Wouldn't that be ok to fullfill specification? Because according to the technical application, a resistance of 1% and 100ppm should be good enough.

    Karina

  • 0 in reply to Karina Espejo
    TI__Mastermind 38230 points

    Karina:

    We do not recommend or recomend  the use of a trimmer to adjust the Vout voltage.

    We only recommend a fixed preset 100PPM resistor on the adjustment pin .

    Any change in tehhe resitance or voltage on the Rset pin will vary the output voltage.

    Tom