S32K I2C open drain FET resistance

[Alex_Raisle]

Hello everybody,

i use I2C at the S32K144 with external Pull Up Resistor.

Is there a specification about the Rds_on of the internal FET which pulls the line down to GND?

Best regards, Alex

[Daniel-Aguirre]

Hi,

Rds_on is not typically given on the MCU's datasheet. The specification given is the current it can handle.

UM10204 gives a brief explanation on how to calculate the minimum and the maximum Pull-up resistor [Page 50, UM10204, Rev 7.0, 10/2021] with typically given electrical specifications.

Please, let us know if this information was helpful or not.

[Alex_Raisle_]

Hello,

in the UM10204 chapter 4.2.3 is written "NXP devices have a higher power set of electircal characteristics than SMBus 1.0. The main difference is the current sink capability with Vol = 0.4V."

Due to the Reference Manual Rev. 10 chapter 50.2 "The LPI2C module also compiles [..] (SMBus) Specification, version 2.

So due to this I assume that Vol = 0.4V at this µC if I limit the current to 3mA?

Best regards, Alexander

[Daniel-Aguirre]

Hi,

For the case of S32K1xx, datasheet shows V_OL(max) as 0.8V and I_OL as 5mA (Whitin IolGPIO-HD_DSE_0 @ 5V). With this, you will have the minimum value for Rp, anything above that (and below the maximum Rp calculated with Eq 1) should be fine.

These should be the values that UM10204 refers to.

Please, let us know.

[Alex_Raisle_]

Hello Daniel,

thank you for the information.

In the datasheet I only find the information that at 0.8V the min. current is 5mA.

How high is the voltage for example at 3mA?

Is there a graph or a data table available?

Best regards, Alexander