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TPS650250: Power off sequence of TPS650250

Lin_Charles
Expert 4260 points
Part Number: TPS650250

Hi, all. I saw in the document "Powering the AM335x With the TPS650250" that we use RC circuit to do the Power-Off Sequence for the TPS650250. We can see that the sequence will DCDC1 to DCDC3 to DCDC2. When SYS_EN=0, assume that Vf of diodes is 0.7V, larger than VIL=0.4 rated in the datasheet, will it be a risk for the customer to power off the Vo_1.1? Another question is that if EN=0, the voltage of EN3.3 will also larger than 0.4V. How can we make this power-off sequence right? 

  • 0
    TI__Mastermind 30260 points
    Lin,

    These are Schottky diodes (www.onsemi.com/.../MBR0540T1-D.PDF), which tend to have a much lower VF (forward voltage) than regular diodes.

    The forward voltage will likely be 0.4-0.5V under most circumstances (except at -40 degrees C), and the VIL value of most TPS650250 devices will actually recognize a low value above 0.4V

    This is why this design works, and the AM335x+TPS650250 has been thoroughly tested using these Schottky diodes, but if you want to guarantee VF is always <VIL then you would need to pick a different Schottky diode to ensure VF<VIL under all corner cases across temperature.