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DP83867IR: LED Configuration

Kailyn Chen
Genius 9560 points

Part Number: DP83867IR

Hello,

Please help to check  the below connection is worked strap mode 1 for LED_0? Because 1.8-V supply results in dim LED lighting, so the customer referred to Figure 27 for a possible implementation of this functionality. 

Best regards

Kailyn

  • 0
    TI__Genius 11725 points

    Hi Kailyn,

    You mention this is a screenshot from Figure 27, which document is this captured from?

    Strap modes are determined by the voltage sensed on the strap pin. If the PHY is using a 1.8V supply for VDDIO, the strap pins, including LEDs should be pulled up to 1.8V. Pulling the LED pin up to 3.3V while a 1.8V supply is used for VDDIO will result in an incorrect strap mode.

    Thank you,

    Nikhil

  • 0 in reply to Nikhil Menon
    TI__Genius 9560 points

    Hello Nikhil,

    Thank you for your reply, and the Figure27 is from datasheet of 8.5.3 section, please refer to the below picture.

    Best regards

    Kailyn

  • 0 in reply to Kailyn Chen
    TI__Genius 11725 points

    Hi Kailyn,

    Yes this configuration you have shown should be ok.

    Thank you,

    Nikhil

  • 0 in reply to Nikhil Menon
    TI__Genius 9560 points

    Hello Nikhil,

    This configuration of LED_0 is strap mode 0 or strap mode 3?Because  the datasheet describes the strap mode 0 of LED_0 is pulled down to GND. 

    Best regards

    Kailyn

  • 0 in reply to Kailyn Chen
    TI__Genius 11725 points

    Hi Kailyn,

    To clarify, DP8386IR/CR datasheet defines the strap modes as mode 1-4. The strap settings can be found in section 8.5 of the datasheet. The image you have shown above would be consistent with a mode 1 setting. Figure 27 shows a mode 2 setting. To convert Figure 27 to mode 3, the 10k resistor should be replaced by a 5.76k resistor. 

    Figure 26 in the datasheet, showing the direct pull-down to GND, is the mode 1 configuration used for a higher VDDIO level. As you mentioned the desired VDDIO level is 1.8V, the recommended mode 1 configuration would be as you have shown above, to ensure the LED will illuminate as expected. 

    Please let me know if you have any further questions.

    Thank you,

    Nikhil