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DP83822IF: configure DP83822IF

Dam Cuong
Prodigy 40 points
Part Number: DP83822IF
Other Parts Discussed in Thread: DP83867IR

Dear all Experts,

Please explain how to use table 11 in datasheet to configure DP83822IF, such as: hard boot strap mode by hardware configuration (external resistor, pin need pull up/ down, default mode ...); soft boot strap mode by firmware configuration (access registers and configure by MDIO and MDC by MCU after power up and save configuration, hard configuration if need).

I do not know exactly what I have to do to get correctly configuration from datasheet!

In additional, what I can do to use LED on pin 17 and pin 24 if I use VDDIO = 1.8V because LED has forward voltage?

Please reply soon!

Thanks and Best regards!

Cuong

  • 0
    TI__Mastermind 23675 points
    Hi Cuong,

    You need to use table 11 to identify the mode of operation (MODE 1 - 4) required to get the PHY settings you want in tables 12-15.
    For instance, the CRS pin is a bootstrap pin and if you want to have both LED SPEED and LED CFG enabled, you set that pin to MODE 3.
    Then you see how MODE 4 is default. This means that CRS has an internal pull-up resistor.
    Based on that, you can use table 9 as a suggested starting point for external resistor selection.
    However, you should use the thresholds specified in table 10 to get the most centered value.

    All bootstrap settings can be overridden.

    For the case with 1.8V and LEDs, you can use a BJT or FET. The DP83867IR datasheet (figure 26) has an example of this method if you need help visualizing it.
  • 0 in reply to Ross Pimentel
    Prodigy 40 points

    Hi Ross Pimentel,

     

    Thanks a lot for your support!

    As you suggested "All bootstrap settings can be overridden", I want to use MDIO/MDC interface to configure DP83822 (strap function, ...) because I want reduce components on PCB.

    Please suggest the mandatory pins that I have to configure by external pull up/down resistors to DP83822 is ready for configuration from MCU by MDIO/MDC interface after power up ?

    Please reply soon!

    Best regards!

    Cuong

  • 0 in reply to Dam Cuong
    TI__Mastermind 23675 points
    Hi Cuong,

    The only one required is RX_DV strap since this affects the clock divider option.
    If you want MII operation, please put a pull down on this pin.
    If you want RMII operation with a 50MHz clock, please put a pull-up on this pin.
    If you want RMII operation with a 25MHz clock, please strap to mode 3 by placing a pull-up and pull-down as specified in table 9.
    pull-up around 5.76k ohm and pull-down around 2.49k ohm
  • 0 in reply to Ross Pimentel
    Prodigy 40 points

    Hi Ross Pimentel,

    Thanks for your support!

    If I use RGMII interface at 25MHz reference clock, I need configure RX_ER ( pin 28) to mode 3 and RX_DV (pin 26) to mode 1 (no external pull up/ down resistor) or mode 3 (external pull up and down resistor) ?

    Please reply soon!

    Best regards!

    Cuong

  • 0 in reply to Dam Cuong
    TI__Mastermind 23675 points
    Hi Cuong,

    Mode 1 is fine for RX_DV and mode 3 for RX_ER.
  • 0 in reply to Ross Pimentel
    Prodigy 40 points

    Hi Ross Pimentel,

    Thank you so much!

    I have final question about TPI network circuit:

    I supply for DP83822 AVD = 3.3VDC, refer to "9.2.1 TPI network circuit", " Center tap of the transformer must be connected to analog supply rail (AVD) with decoupling capacitors close to the transformer", please let me know that I can connect center tap of transformer to 3.3VDC source from other source on PCB (common GND with 3.3VDC supply to AVD of DP83822) ?

    please reply soon!

    Best regards!

    Cuong

  • 0 in reply to Dam Cuong
    TI__Mastermind 23675 points
    Hi Cuong,

    You can connect to a different supply, but both supplies must be on at the same time for the PHY to operate.
    Just make sure that AVD and the other 3.3V rail come up at the same time.