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UCC27211A-Q1: ucc27211

user1980346
Prodigy 20 points
Part Number: UCC27211A-Q1
Other Parts Discussed in Thread: UCC27211, UCC27201

The datasheet of ucc27211 indicates that the pull-up and pull-down resistor both are 0.9R. However,what's the meaning of pull-up and pull-down resistor? Is it the Rdson of  totem-pole MOSFET? Or the driving resistor of external MOSFET built-in the ucc27211? Or other thing else?

When calculating the souring anf sinking current during miller effect,is it appropriate just considering the 0.9R and neglecting the Rdson of  totem-pole output stage MOSFET?

pls give the pull-up and pull-down resistor of ucc27201 for comparisn.

Hoping for your timely reply.

  • 0
    TI__Intellectual 2910 points

    user1980346,

    The pull-up and pull-down resistor value of 0.9R refers to the rDSON of the respective driver output stage MOSFETs. The equivalent for the UCC27201 is around 1.35R.

    I hope this post answers your question. If it has, please press the "Verify Answer" button below.

    - Daniel

  • 0 in reply to Daniel Ruiz
    Prodigy 20 points
    Thanks for your reply.
    Then I have another question about the 4A peak current. Wheather the ucc27211 integrate current limiting function to gurantee sourcing and sinking current not exceeding 4A?
    For example,
    If the power supply for ucc27211 is 12V and the miller voltage of external MOSFET is 4V. If the external gate resistor for driving MOSFET is 2R. Then the sourcing current during miller effect is (12-4)/(0.9+2)=2.7A. Is this calculating method right?
    However, If choosing 0.5R as gate resistor. The sourcing current during miller effect is (12-4)/(0.9+0.5)=5.7A,which exceeding the peak value 4A. Will the ucc27211 limit the sourcing current as 4A.
    Hoping for your timely reply.
    Thanks!
  • 0 in reply to user1980346
    TI__Intellectual 2910 points
    These UCC2720x and UCC2721x drivers do not have a current limiting function. The peak current spec is based on typical performance. Note that there is a capacitive load due to the gate of the MOSFET that affects the shape and timing of the max current output. Also, the driver's internal pull-up and pull-down are MOSFET devices with dynamic behavior unlike an ideal switch. The 0.9R descriptor for these output resistances is a DC spec that does not capture all the transient behavior of the driver output stage.