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ESR capacitor value for TPS76618

Christophe LEROUX
Prodigy 10 points

Dear,

We use a TPS76618 with 3,3V on input voltage. Current consumption on1V8 output is 100mA.

In the datasheet, there is no data for ESR value with 1V8 output. Is there a formula, because we have a ripple problem with an 3Ohms ESR, and we can see failure with PG signal. (voltage falls under minimum value)

There is only curves with instabily area outside 100mOhms and 20Ohms.

We use a 4.7µF tatalum capacitor (with 2Ohms ESR max) and 1Ohm series resistor.

We have replace 1Ohms resistor by 0 Ohms and it's works....

Have you a formula ?

Thanks

 

  • 0
    TI__Guru 55940 points
    Please excuse a delay in response due to the US Holiday.

    Very Respectfully,
    Ryan
  • 0
    TI__Guru 50170 points
    HI Christophe,

    The application recommendation is to have an effective ESR of 0.3Ohms. 10Ohms may be stable but would induce a lot of ripple as a function of the change in load current. If you are using a tantalum capacitor, there is no need to add a series resistor. Normally this would be done if you were using a ceramic capacitors. This is why it works when you use a zero Ohm resistor.

    I hope this helps.