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Original question:

TCA9517-Q1: EN behavior

TCA9517-Q1: Output behavior when EN=L

Yuto Kitamura
Expert 7155 points

Part Number: TCA9517-Q1

Hi team,

I posted the e2e below and got answer, when EN=L, Output becomes Hi-Z. But my customer says, it doesn't seems to work as answered in the e2e.

Can you please re-check output really becomes Hi-Z when EN=L?

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1228072/tca9517-q1-en-behavior?tisearch=e2e-sitesearch&keymatch=pca9517#

Best regards,
Yuto

  • 0
    Guru 320330 points

    The EN input must be low, not floating.

    What exactly did the customer measure? (The TCA9517-Q1 has open-drain outputs, so I guess a line was pulled low?)

  • 0
    TI__Guru 55808 points

    Hi Yuto,

    Yes output becomes Hi-Z when EN = L, but that doesn't stop the output node from being pulled up HIGH by a pull-up resistor in the system. The 9517 buffer is only able to drive a LOW signal logic towards GND. When the drivers turn off EN = L, the drivers simply release the bus and allow it to "float" to whatever voltage is being presented to the bus line. If a pull-up resistor exists, then that "floating node" would be pulled up to whatever voltage the resistor is connected to. 

    If the customer has a schematic on-hand, I can look over the device connections to see if there are any incorrect connections surrounding the EN pin.

    Regards,

    Tyler