MPQ8626 Enable Input Current

DC-DC Power Converters
1

Hi MPS team,

Now, i use 3V3 to drive EN pin through 4.7k resistor. But i see in page 17 of MPQ8626 datasheet the equation to calculate Rup resistor. The resistor must be large enough to limit current come to EN pin does not exceed 50uA. It’s mean, if i use 3.3V to drive, i need use R pull up > 66k. is it correct ?
I think as normally, i will design to ensure that the voltage in EN pin does not exceed 4.5V, and dont care about R pull up resistor.

2

Hello,
Welcome to the forum.

Yes, you are correct. Typically, we recommend using 100k pull up resistor.

Let me know if any further questions.

Regards,

Yash Shah

1 Like
3

Hi Yash,

Thank you for your confirmation.
I have 2 more question:

  1. Could I use the 3V3 push-pull output to drive directly EN pin?
  2. In the case I use 12V and 2 resistor to implement voltage divider to 3.3V or 2V, should both 2 resistor > 100k ? now I use 17.4k and 4.7k resistor
4

Some rando on the internet, but to me it looks like you can use a voltage source to drive the Ven Up to 3.6V. So direct drive from 3.3V logic no problem. If your source is higher than 3.6V then they have to worry about limiting the current to under 50uA. It looks like the internal logic of the chip runs off 3.3V so the 3.6V is where the body diodes of the input gate are going to start conducting and lifting the 3.3V rail possibly causing harm.

1 Like
5

Hello,
Yes, you could use the push-pull to drive EN pin, but remember the part wont be powered on if the output of push-pull is not coming up.

It depends on your application, if you want the MPQ8626 to be powered on only if the push-pull is working fine, then you could go with it.

For the voltage divider resistors, I would suggest going with >100k.

Regards,

Yash Shah

1 Like