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DP83TG720S-Q1: Schematic review

yuki kawamura
Prodigy 10 points

Part Number: DP83TG720S-Q1
Other Parts Discussed in Thread: DP83TG720EVM-MC

I have designed a media converter for 1000BASE-T1 and 1000BASE-T, and I have created the circuit diagram, so I would appreciate your review.
I based the circuit design on the DP83TG720EVM-MC, but the design assumes configuration via jumper settings only, without using a microcontroller.

Ethernet Media Converter.pdf 

  • 0
    TI__Expert 3546 points

    Hi Kawamura-san,

    I will review by the end of this week. 

    Best,

    Charles

  • 0
    Prodigy 10 points

    Hi Charles-san,

    Thank you. I hope to see your review.

    Regards,
    Kawamura

  • 0 in reply to yuki kawamura
    TI__Expert 3546 points

    Hi Kawamura-san,

    Please see my comments below:

    1. DP83TG720 should be strapped in autonomous mode (Pin 6 pull down). Please follow configuration of DP83TG720EVM-MC: 
    2. If you intend to set DP83TG720 in master mode, pin 35 should be pulled up with 2.49k resistor. Please follow circuit below: 
    3.  RGMII connections between DP83TG720 and DP83867 look OK. 
    4. DP83867 strapping looks OK. 
    5. Please double check your design with the schematic checklist of DP83TG720 and DP83867. This can be found on the device's respective product page.  

    We strongly recommend to use a microcontroller to access SMI registers of both devices. DP83TG720 requires a set of register writes for best interoperability and EMC performance. Also, having SMI access will be a great help for debugging if the need arises.  

    Best,

    Charles

  • 0
    Prodigy 10 points

    Hi Charles-san,

    >1

    According to the datasheet, when the strap mode is set to 1, the strap resistor is listed as open.
    Should this be configured as a pull-down resistor?

    >2

    Understood.

    >5

    Sure.

    Regards,

    Kawamura

  • 0 in reply to yuki kawamura
    TI__Expert 3546 points

    Hi  Kawamura-san,

    >1

    The logic level sampled by the strap determines the active state of the LED output driver. In Mode 1, strap will sample as pull-down because of pull-down internal to PHY. LED will not function correctly if it's pulled up as shown in your schematic: 

    Please follow figure 16.9 in the datasheet for strap config with LED.

     

    Best,

    Charles

  • 0 in reply to Charles Wang
    Prodigy 10 points

    Hi Charles-san,

    I understand. A pull-down resistor is required in parallel with the LED on pin 6.
    Since I intend to use pin 35 in slave mode, does that mean a pull-down resistor is required there as well?
    Also, I assume switching to pull-up mode via SW1 requires changing the pull-down resistor connected in parallel with the LED to a pull-up resistor as well?

    Regards,

    Kawamura

  • 0 in reply to yuki kawamura
    TI__Expert 3546 points

    Hi Kawamura-san,

    Please follow the strap configuration shown in Figure 6-19 for all LED pins that are use for bootstrapping.

    Since pin 6 and pin 35 on DP83TG720 should be strapped as pull-down, follow the pull-down strap with LED configuration shown on the left of Figure 6-19. 

    yuki kawamura said:
    Also, I assume switching to pull-up mode via SW1 requires changing the pull-down resistor connected in parallel with the LED to a pull-up resistor as well?

    I'm not sure where SW1 is on your schematic. If SW1 is an LED pin with strap capability, please follow LED configuration shown in Figure 6-19. 

    Best,

    Charles