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PROCESSOR-SDK-AM335X: I2C Low MAX Input Current

howard shih
Intellectual 260 points
Part Number: PROCESSOR-SDK-AM335X

Hi,

Our hardware member wants to know the MAX current injected into am335x I2C pins while the bus is pulling low.

The pins are D17, D18, and VDDSHV6 is 3.3V.

We've read datasheet  p.89 - DC Electrical Characteristics (continued), and the I2C user guide p.14 - Signal Descriptions parts.

But still not sure which value is the right one.

*We use a photo to separate the primary and secondary side. However, there are some issues on the I2C bus. (w/o photo, everything is OK.) 

 

- Howard

  • 0
    TI__Guru 55375 points

    Are you asking current sinking capability of these pins when driving low? If so, this is defined to be 4mA in the Pin Attributes table found in the datasheet.

    I'm also not sure what "use a photo to separate primary an secondary side" means. Are you say the customer is inserting an photocoupler in the path? Can you provide a snapshot of their schematic showing photocoupler connectivity and part number?

    Regards,
    Paul  

  • 0 in reply to peaves
    Intellectual 260 points

    Are you asking current sinking capability of these pins when driving low? 

    > OK, so 4mA is confirmed. It seems that IOH = 4 mA and IOL = 4 mA are both constant, so it is not configurable?

    - Howard

  • +1 in reply to howard shih
    TI__Guru 55375 points

    The output buffers were never expected to source/sink steady-state loads. However, they should be able to source/sink steady-state loads up to 4mA. This limit is not configurable. We prefer external buffers to be used when needing to source/sink steady-state loads as this minimizes power dissipation in the device.

    Regards,
    Paul