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TLC7705M: Threshold Voltage (VIT+) of TLC7705

May
Genius 9880 points
Part Number: TLC7705M

Hi Team, 

Customer is looking for the Threshold Voltage (VIT+) of TLC7705. Below is the inquiry.

"I am trying to find the upper threshold voltage, VIT+, of the SENSE pin that causes the RESET outputs to change value. I have only been able to find a value for VIT- on the datasheet. And how long of a time does the input to SENSE need to be above the threshold for it to trigger the RESET outputs to change?"

Regards,

Maynard

  • +1
    TI__Mastermind 38435 points

    Hi Maynard,

    TLC7705 has a threshold voltage of 4.55V.  It is defined, although it is not stated in the datasheet for some odd reason, that VIT+ = VIT- + Vhys.  Therefore, the TLC7705 has a VIT+ = 4.55V + 70mV = 4.62V.

    I hope I have answered your question.  Please click on "resolved" if there are no further questions.  Thanks!

    Ben

  • +1 in reply to Ben C
    TI__Mastermind 38435 points

    Hi Maynard,

    I forgot about your second question.  See below:

    Ben

  • 0 in reply to Ben C
    TI__Genius 9880 points

    Hi Ben, 

    Thank you for your kind response. Customer has a follow up question regarding this. 

    "Follow-up question: we have a product with a 5V supply feeding into the TLC7705MJG. It is constantly between 4.8 and 5.3Vdc, well above the 4.62 threshold. I am monitoring pin 5 which is always high when the input stays in this range. From what I understand, the pin 7 voltage is above threshold and should drive pin 5 low, but it does not. So I must be misunderstanding something. However, when we get noise on our circuit that causes the supply voltage (pin 7) to spike over 6Vdc, the output of pin 5 goes low ~300us later. Do you know why pin 5 only drives low after these large spikes rather than constantly?"

    Thank you in advance.

    Regards,

    Maynard

  • +1 in reply to May
    TI__Mastermind 38435 points

    Hi Maynard,

    I believe the customer is not understanding the functionality of the part.  When the SENSE pin goes above VIT+, the /RESET (pin 5) signal should be high which signifies not asserted.  If the SENSE voltage falls below VIT-, then pin 5 should go low (asserted).

    Regarding the voltage spike on pin 7, I am not sure why the /RESET is asserted for 300us.  Can the customer provide a scope shot?  Also, it is advised that if the SENSE line is noisy, a 0.1uF capacitor can be used to filter out the spikes.

    Ben

  • 0 in reply to Ben C
    TI__Mastermind 38435 points

    Hi Maynard,

    Any updates from the customer on this issue?

    Ben

  • 0 in reply to Ben C
    TI__Genius 9880 points

    Hi Ben,

    Thank you for your support.

    This answer the customer query.

    Regards,

    Maynard

  • 0 in reply to May
    TI__Mastermind 38435 points

    Hi Maynard,

    Glad to be help!  Good luck!

    Ben