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TPS40170 Enable Pin Question

MikeH
Guru 15580 points
Other Parts Discussed in Thread: TPS40170

The TPS40170 data sheet says the ENABLE pin voltage should not exceed 8.8V (Absolute Maximum Ratings, page 3). However, in the Functional Description seciton you state

If the ENABLE function is not needed for the design, then it is suggested that the ENABLE pin be pulled up to VIN by a high value resistor ensuring that the current into the ENABLE pin does not exceed 10 µA.

Since VIN can go up to 62V, does this mean that the ENABLE pin can also go to 62V?

Also, requiring that the VDIS (ENABLE Disabled voltage) is below 100mV is a tough requirement! Is this the correct lower voltage limit?

 

  • 0
    TI__Mastermind 32360 points

    Hi Mike,

     

    If your Vin go above 8.8V, use a resistor divider as described in the datasheet as follows:  

     

     

    “The ENABLE pin must not be allowed to float. If the ENABLE function is not needed for the design, then it is suggested that the ENABLE pin be pulled up to VIN by a high value resistor ensuring that the current into the ENABLE pin does not exceed 10 μA. If it is not possible to meet this clamp current requirement, then it is suggested that a resistor divider from VIN to GND be used to connect to ENABLE pin. The resistor divider should be such that the ENABLE pin should be higher than VEN and lower than 8 V.”

     

    To disable the device Ven<Vdis=100mV

    To enable the device  8.8V>Ven>600mV

     

     

    Thanks!

    Tahar

  • 0 in reply to Tahar Allag
    Guru 15580 points

    Tahar,

    What we have here is a failure to communicate. My question was about the maximum allowable voltage on the ENABLE pin. The wording above seems to imply that ENABLE can be pulled up to Vin, which can go to 62V. The warning in this sentence is to limit the current to 10uA, but there is not warning to limit the voltage. Can ENABLE be pulled to 62V? Your comment about using a resistor divider does not tell me what the maximum allowable voltage on the ENABLE pin can be.

    MikeH

     

  • 0 in reply to MikeH
    TI__Mastermind 32360 points

    Hi Mike,

     

    The maximum allowable voltage on the enable pin (Ven) is 8.8V. You can not go above 8.8V based on the absolute maximum rating table on page 3 in the datasheet. You can connect your Ven directly to Vin if your Vin is below 8.8V. If Vin goes above 8.8V then use a resistor divider from Vin to GND as described in the datasheet.  

     

    Please let me know if you have more questions.

     

    Thanks!

    Tahar