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DS26LV31T: DS26LV31T EN and EN*

Moshe Levy
Prodigy 230 points

Part Number: DS26LV31T

Hello, 

I would like to ask the following questions:

1. In the company i work, i saw a design of this IC with both the EN and EN* tied to GND. Is such case being correct? I mean, from Table 8-1. Truth Table of the datasheet

i might be correct (and it does on the field). but is such connection is correct one or need only to connect say the EN to high?

2. should the EN (or EN*) be connected to Vcc via a 4.7K resistor (or 4.7K P.D for EN* ) In order to keep the driver high-impedance during power-up (when the MCU I/Os are commonly high-impedance too)?

thank you

  • +1
    TI__Guru 74302 points

    Moshe,

    Thanks for bringing this to E2E.

    1. Yes, this is a correct configuration. The EN and EN* feed into a logical OR, so if either is tied to the correct voltage, the device will be enabled fully.

    2. A pull-up or pull-down is not required, but will only further protect the logic pin in the case that you mentioned, or in case there is inrush current at power up.

    Please let us know if you have any other questions.

    Regards,

    Eric Hackett 

  • +1
    Prodigy 230 points

    Hi Eric,

    Thank you for the prompt reply. 

    1. you say "if either..." but in the design both are tied to GND. Is this a good connectivity? design wise?

    Thank you...

  • 0 in reply to Moshe Levy
    TI__Guru 74302 points

    Moshe,

    Yes, since the EN* is active low, and the logic for enabling using the EN and EN* is a logical OR, if one is correctly enabled, then the device is correctly enabled. If both were tied to a logic high voltage, the case would be the same, since EN is active high, the voltage on it would enable the device correctly while EN* would not.

    Regards,

    Eric Hackett