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Original question:

TPS7A8500 sequence requirement

TPS7A85: Max voltage on EN pin

Jeff Xie
Intellectual 1780 points
Part Number: TPS7A85

Hi team,

See figure 1, the maximum value of Ven is VIN, is the VIN input voltage must be less than or equal to VIN? But the second figure VIH can reach 6.5V.

If our Vin is connected to 2.5V, can the EN pin be connected to 3.3V signal input?

thank you!

  • 0
    TI__Mastermind 43580 points

    HI Jeff,

    This is correct for the TPS7A85. VEN should not be higher than VIN. However, we removed this restriction on the TPS7A85A. 

    This is a pin to pin drop in enhancement. 

    I hope this answers your question. 

  • 0 in reply to JCHK
    TI__Intellectual 1620 points

    Hello,

    This topic is confusing despite running circles around it for a while now.

    The table shown under 6.1 is for Abs Max Rating. EN<7V
    By definition this is not recommended for the normal part usage.

    Under the 6.3 Recommended Operating Conditions - which should govern the design - the VEN is still maxed the VIN.

    On page3, under Pin Functions EN can be connected to VIN or VBIAS.

    As a use case when VIN=1.1V, VBIAS= 3.1V and EN comes from say a UCD90k sequencer, the drive is 3.3Vwhich is a spec violation.

    Could you please clarify and correct the datasheets for the TPS7A8xA family.

    Thank you

  • 0 in reply to Cosmin P
    TI__Mastermind 43580 points

    Hi Jeff,

    I can see how this can be a bit confusing. The recommended section is making a practical recommendation. Meaning, what are the benefits of driving EN higher than VIN?

    Page 3 is correct in that you can tie EN to either VIN or VBIAS. For the TPS7A8xA series, it is really up to you. 

    The Abs Max Ratings are simply lines that you should not cross. Meaning, if used above the abs max ratings, the device could be damaged. We like to have some margin between the recommended max rating and the abs max rating. 

    Does this help to clarify?

  • 0 in reply to JCHK
    TI__Intellectual 1620 points

    Thank you, but not really...

    As per the post, this is a real case:

    VIN=1.1V, VBIAS= 3.0V and EN comes from say a UCD90k sequencer, the drive is 3.3Vwhich is a spec violation.

    What if the EN drive would come from an upstream switcher with the PG pull-up resistor connected to 5V?

    This is against the spec, and formally holds a product release.

    What is the limitation for the EN input - a high impedance input.

    Is there an ESD element clamping the voltage to VBIAS or VIN?
    Is there a current limit for this element? - this can be solved with a resistor in series with EN as long as the pull-up voltage is less than Abs Max specified 7V


    Can we get a clear answer for this topic please which can actually lead to a solution.

    Thank you

  • 0 in reply to Cosmin P
    TI__Mastermind 43580 points

    I confirmed that the VIN=1.1V, VBIAS= 3.0V and EN  being driven at 3.3V is absolutely not a spec violation. This is a datasheet error.

    I hope this clears this up.