i.MX8M - GPIO current source & sink capability - Drive Strength

[Haider_Ali]

Hello,

I have a basic question regarding the current source and sink capability of i.MX8M Quad processor.

What I understand from the datasheet & reference manual is we can configure some parameters for pad by writing to pad CTL register for I/O pins (IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO09 as example).

Now the drive strength (current source & sink capability) of GPIO pin is based on the value configured for DSE field of the register as shown in below picture:

So from this,

Q1: If DSE is 001 and VDD is 3.3V then the current I can source or sink through that pin would be equal to 3.3V/255Ohm = 12.9mA ? or is there more to it that needs to be considered?

Q2: Can this DSE be explained as a series resistor between the driver and the load that will be connected to the I/O pin? So in actual this resistor is acting as a current limiter?

link to the processor:

https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/i-mx-applications-proces...

Thank you

[JorgeCas]

Hello,

Q1: Yes, that is correct, and it is the only thing you need to consider. You can use this thread as reference.

Q2: We don't have an exact representation of the pre-driver structure but should be something like this:

But yes, something like that. The "series resistor" you mentioned is certain by the transistor array output impedance of the pre-driver.

Best regards.

[Haider_Ali]

Thank you.

So just to be clear, does this means that even if I connect 3.3V supply directly to I/O pin and set the pin as output and drive it as low (or vice versa i.e. connect GND to I/O pin and drive it high), the amount of current that will flow will limit by this series resistance / output impedance and will not be a short circuit?  

[JorgeCas]

Hello,

Yes, that is correct. But it is recommended to limit that current and do not "short circuit" the GPIO on that way.

Best regards.