PF8200 pull up resistor strength

[adevries]

Hello,

I'm using the PF8200 in a design, and I had some questions about the pull-up resistors recommended by the PF8200 datasheet. For signal pins INTB and PGOOD, the datasheet recommends pulling the signals high with a 100k resistor, and for signal FSOB, the datasheet recommends pulling the signal high with a 470k resistor. How were these recommended resistance values originally determined? Why is the FSOB pull-up resistor value different than the INTB and PGOOD pull-up resistor value? For my application, I initially followed the suggestion of the datasheet and used 100k resistors and a 470k resistor, but it now appears that the input pins sensing these signals have large leakage currents, so I may need a stronger pull-up resistor on these lines. Would it be acceptable to pull these lines high with 10k resistors? What about 1k resistors?

Thanks

[guoweisun]

Hi

What do you mean about -input pins sensing these signals have large leakage currents?

Do you have more information about that?

[adevries]

Hi G.w. Sun,

Please see the image below for a simplified example. In this example, I have FSOB, PGOOD, and INTB pulled high by the recommended resistor values. I then have them being sensed by the GPIO pins of an i.MX 8M Mini. However, when configured as an input, the leakage current into these pins is about 15uA. Because of the high resistance, the leakage current is causing there to be a 1.5V drop across the pull-up resistor (15uA * 100k ohms = 1.5V), making it appear as though the lines are low when they aren't.

Does that help explain what I mean when I said that my input pins have large leakage currents?

Thanks

[guoweisun]

HI

I don't know more information about structure GPIO inside of I.MX,if the 13uA is normal after configure it as input function,I think you can reduce the pull up resistor to 10K to try,but this will bring your more current consumption.

[adevries]

Hi G.w. Sun,

Thanks for the response. Increased current consumption is acceptable in my design as long as the PF8200 can handle the stronger pull-up resistors. This leads back to my original questions:

How were these recommended resistance values originally determined? Why is the FSOB pull-up resistor value different than the INTB and PGOOD pull-up resistor value? Would it be acceptable to pull these lines high with 10k resistors? What about 1k resistors?

Thanks

[guoweisun]

The INTB/FSOB/PGOOD are open drain structure,they are similar inside circuit.

Suggest you limit the carry current 1mA then to calculate pull up resistor.