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REF4132: VIN input slew late

Shuji Ishiwata
Mastermind 7885 points
Part Number: REF4132

Hi All,

I have a question about REF4132.

If VIN has already been input, I think that it is possible to input to EN with resistive voltage division. is my understanding correct?

Also, according to the data sheet below, the rise of VIN is 6V/msec. Don't you need 6V/msec slew rate if you input EN later?

Does this condition assume that VIN and EN are entered at the same time or EN is entered first?

Best Regards,
Ishiwata

  • 0
    TI__Genius 11401 points

    Hi Ishiwata 

    Vin should come either together or before EN. 

    Slew rate for EN pin can be faster as it is digital pin. 

    Regards

    Trailokya

  • 0 in reply to Trailokya Rai
    Mastermind 7885 points

    Hi Trailokya,

    Thank you for your reply.
    I understand that it is possible to input to EN with resistive division.
    Also, I understand that I don't need 6V/msec because I plan to input EN after VIN is slowly input.

    Is my understanding correct?

    What are the cases where VIN needs a slew rate of 6V/msec?

    Thank you for your wonderful support.

    Best Regards,
    Ishiwata

  • 0 in reply to Shuji Ishiwata
    TI__Genius 11401 points

    Hi Ishiwata 

    You may see overshoot if VIN has is <6V/ms. If it has faster then you will not see it. 

    Regards

    Trailokya 

  • 0 in reply to Trailokya Rai
    Mastermind 7885 points

    Hi Trailokya,

    Thank you for your reply.

    Will there be an overshoot if EN is entered after VIN is fully entered?
    I understand that the rise time of VIN is irrelevant if EN is not entered.
    Is my understanding correct?

    Best Regards,
    Ishiwata

  • 0 in reply to Shuji Ishiwata
    TI__Mastermind 18131 points

    Ishiwata-san,

    We will respond on Feb 28. Thanks.

  • 0 in reply to Masoud Beheshti61
    TI__Genius 11401 points

    Hi Ishiwata San 

    The behavior of Enable pin startup is given in figure 13 (page 8)

    What is your turn on settling tiem ? 

    REF35  doesn't have any oveshoot. If you are specificly concern about overshoot. 

    Regards

    Trailokya 

  • 0 in reply to Trailokya Rai
    Mastermind 7885 points

    Hi Trailokya,

    Thank you for your reply.

    I understand that even if EN is input after VIN is input, a slight overshoot will occur.

    The customer is inputting the input to EN with a voltage divider resistor as in the circuit below.

    Overshoot occurs, but is there any particular problem with how the device is used?

    Best Regards,
    Ishiwata

  • 0 in reply to Shuji Ishiwata
    TI__Genius 11401 points

    Hi Ishiwata 

    • Thre will not be any problem with the overshoot. The device will work normaly. 

    Why you are using a resistor devider with EN pin?  You can diretly short wit with EN pin. Extra resistors will burn some current?  Can you please tell the values of the resistors. 

    Regards

    Trailokya 

  • 0 in reply to Trailokya Rai
    Mastermind 7885 points

    Hi Trailokya


    Thank you for your reply.

    Confirmed to my customer.
    The assumed resistance value is 30kΩ on the VIN side and 20 kΩ on the GND side.
    The reason for inputting to EN by resistance division is as follows.
    Because it delays the input to EN. I want to make the rise slower than VIN.

    I will always appreciate your kind support.


    Best Regards,
    Ishiwata

  • 0 in reply to Shuji Ishiwata
    TI__Genius 11401 points

    Ishiwata San 

    Thanks for your confirmation.  This should work fine. This should work fine if VIN is >=4.0V as EN ris is 1.6V. 

    Regards

    Trailokya