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DP83822I: What kind of problem is coming when 2.2Kohm PU or PD resistor is co-existed with strapping resistor?

YoungYun Kim
Intellectual 410 points
Part Number: DP83822I

To the person concerned

Regarding strapping related pins on DP83822, I have question.

At pin fuction table, I found below notice relevant to strapping pins 

"f) Type: S-PU, S-PD - Strapping Pin (All strap pins have weak internal pullups or pulldowns. If the default strap value is needed to be changed then an external 2.2-kΩ resistor should be used)

In order to make intended operation , Datasheet recommends to apply 4-Level bootstrap and specifies PD or PU resistor values for each of 4-Level cases.

qustion is that what happen if external 2.2-kΩ resistor is co-existed with resistor matrix for 4-level strapping.

For example, in case of BOOSTXL-ETHERCAT reference circuit, external 2.2-kΩ resistors are existed on pins for the strapping. if customer adds another external resistor for 4-Level strapping, What kind of problem can be coming?

in addition, Could you explain when external 2.2-kΩ resistor is needed?

thank you

Best Regards

Mark Kim

  • 0
    TI__Mastermind 23675 points

    You can use any resistor value so long that the resistor combination you use will result in the bootstrap threshold falling within the mode of operation you want.

    A 2.2k ohm is not required. If you are strapping to mode 4, typically, a 2.2k ohm is used, but it is not required. If you are strapping to mode 2 or mode 3, a 2.2k ohm should not be used because you need to set the threshold to get the bootstrap in the correct range.

    Please follow the bootstrap threshold table in the datasheet.