• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 62 subscribers
  • Views 89 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLV840: TLV840MADL32DBVRQ1 Pin 1 o/p not coming initially and after power off & on , output coming

Sooraj Surendran
Prodigy 80 points
Part Number: TLV840

Hi 
Am using TLV840MADL32DBVRQ1 IC for Reset & Voltage Monitoring in my circuit . Below is my circuit .. 

Problem am facing is Initially i power on the board , at pin 1 am not getting the 3.3V . If i switch off and on again , it will give 3.3 v at pin 1 . Please check the circuit and let me know whether circuit is correct .. 

  • 0
    TI__Prodigy 500 points

    Hi Sooraj,

    Thank you for your question!

    The circuit looks correct, but just to confirm, are you switching VDD off and on? 

    The timing of the TLV840 during the power on phase is shown below; the expected output is for the active low RESET signal to be held low (asserted) until VDD goes above VIT+.

    I also noticed that the device threshold voltage is 3.2V while the nominal is 3.3V. With a 5% typical hysteresis, VIT+ = 3.2V + (0.05 * 3.2V) = 3.36V which is greater than the nominal voltage of 3.3V. As a result, when RESET is asserted (VDD drops below 3.2V) it will be difficult to deassert it since it would require VDD to go above nominal. This may be a reason that you are seeing inconsistent results when you power on at different times.

    I hope this helps, and if you have anymore questions, please let me know!

    Best Regards,

    Andrew Li

  • 0 in reply to Andrew Li
    Prodigy 80 points

    Hi 
    Thanks for the reply . 
    Here am using this IC as reset for Microcontroller . So my problem is when board power is on for first time , from this ic pin 1 3.3v is not coming to controller , so controller is reset ... and if again turn on and off power of board , then am getting 3.3v output from pin 1 of this ic .. how can i cover this like during first time itself i should get 3.3v from pin 1 ... 

  • 0 in reply to Sooraj Surendran
    TI__Prodigy 500 points

    Hi Sooraj,

    I think I'm having a little bit of trouble understanding the problem. When you power the board on the first time, are you seeing that the RESET signal never deasserts, even when it should be powered on properly? Then when you turn it off and on the second time, the TLV840 operates as normal?

    If this is the case, I think a good test is to leave the manual reset (MR) pin floating to see if the circuitry you have connected to it is manually asserting the reset. If you are still having trouble, it would be helpful to have some oscilloscope shots to help me understand what problem you are having.

    I hope this helps!

    Best Regards,

    Andrew Li