• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 124 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TL7702A: Issue with Example Circuit

Tarek Mhareb
Prodigy 10 points
Part Number: TL7702A

Tool/software:

Hello,

The example circuit might have a potential mistake that could damage the device.

The RESET output of the bottom TL77 is connected through a 10 kohm resistor that limits the current through the diode. The circuit in the datasheets works because when an undervoltage condition happens on -12V and the diode conducts, the voltage of the RESIN input goes to something around -0.6V to -0.8V and the absolute maximum ratings specification for this input RESIN  is -0.3 V. So, it seems to me that this circuit has the potential of damaging one of the TL77.

Can you please check the circuit and how to deal with two negative voltages at same time ?

Thank you,

TM

  • 0
    TI__Mastermind 18880 points

    Hi Tarek,

    The -.3V limit is based on a positive point of reference, so if either of the 2 top devices on the schematic detects below -.3V in the RESIN, those devices may get damage. On the other hand the bottom device has a negative point of reference which flips the sign of the limit as well.

    Also, this schematic has excited for years now and used by multiple customers. So far, there has been no significant issues reported that we are obligated to remove or configure the recommended schematic on our datasheet.

    Jesse  

  • 0 in reply to Jesse Villanueva
    Prodigy 10 points

    Hi Jesse,

    Yes, but if here is a power failure on the -12V, pin 5 will be low in reference to -12V and the diode will conduct. The voltage on pin 2 will be around -0.6V (diode VF) in respect to gnd.

    TM

  • 0 in reply to Tarek Mhareb
    TI__Mastermind 18880 points

    Hi Tarek,

    We are evaluating your inquiry, we will provide a response in 24hr.

    Jesse 

  • 0 in reply to Jesse Villanueva
    TI__Expert 4080 points

    Hi Tarek,

    We ran the simulation for the negative voltage monitoring output and it does show that the RESIN will see around -0.8V to -0.6V.

    Thanks for bringing this to our attention!

    I will be working with Jesse and the team to make any necessary changes to the datasheet.

    Best Regards,
    Andrew Li