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LSF0102: LSF pull up resistor questions

Mark Chen52
Expert 7245 points
Part Number: LSF0102

Hi Expert:

I have a design question that I want to confirm it with you.

Customer use a level shift IC (LSF0102) between BMC and LAN PHY (RTL8211F) for the management interface.

 

Q1: The level shift IC datasheet shows it needs pull-up resistors on A-side for both MDIO and MDC pins. Can you confirm it?

 

Q2: The datasheet said that No pull-up resistor is needed on the host side (3.3 V) if the LSF family is being driven by standard CMOS totem pole output driver.

If our BMC MDC pin is an output pin with CMOS type, does it mean we do not need add a pull-up on BMC side (B side of LSF0102)?

Regards,

Mark

  • 0
    Guru 299450 points

    The LSF requires pull-up resistors at all pins that can be outputs, and at pins that are inputs and are driven by open-drain outputs.

    If the MDC output of the BMC is open-drain, then a pull-up resistor is needed. If the MDC output is push/pull, then a pull-up resistor is not needed.