MP8795H with external bias

DC-DC Power Converters
1

A few questions I have:

  1. When using external 3.3V bias, do I just connect VCC directly to 3.3V?

  2. When VIN fluctuates from 3V to 6V, what is behavior of the internal VCC LDO when VCC is externally biased? Is it safe to do so?

  3. Is there power sequencing requirement between external 3.3V on VCC and VIN? In other words is it safe to have one supplied but the other is off?

  4. Copied from datasheet:
    “MP8795H is stable in the entire operating input and output voltage ranges with a proper design of the output L/C filter.”
    Question: do you have tool for L/C selection? do you have tool to calculate phase margin and cutoff frequency?

Thanks… Yang

2

Any comments MPS support staff?

3

Hello Yang,

  1. Yes, you may supply 3.3V directly to VCC pin from external bias.
  2. It would be safe to operate between 3-6V input range, if you have VCC externally supplied.
  3. Yes, if you are operating at low input thresholds, its best to have VCC powered before powering input. However, there are no issues if VCC is powered, while input is not. Otherwise, you will hit input UVLO.
  4. You may utilize page 15 of datasheet, and we have MPSmart simulation tool as well.

Best,
Nouman