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TPS3780: Early Warning Detection in TPS3780

Bhargav Jyoti Saikia
Intellectual 420 points
Part Number: TPS3780
Other Parts Discussed in Thread: TPS3779

Hi,

As described in the datasheet, for Early Warning Detection, TPS3779 is recommended. However, I am thinking of using TPS3780  because I need the output high logic level at 4.2V which is greater than Vdd of 1.8V. But, in the datasheet the recommended application for TPS3780 is Monitoring Two Separate Rails with four resistors. So, can I use the TPS3780 for Early Warning Detection using three resistors?

Thanks.

  • 0
    TI__Genius 12630 points
    Bhargav,

    Yes, you can use TPS3780 for Early Warning Detection using three resistors for between VDD of 1.8V and Sense1, between Sense1 and Sense2, and between Sense2 and GND. If you use TPS3780, you need the pull-up resistors on each output because these are open-drain output types so pull-up resistor is required.

    Please let me know if you have any other questions. Thanks!


    -Michael
  • 0 in reply to Michael_DeSando
    Intellectual 420 points

     Thanks Michael,

    That helped a lot. Also, in the recommended application circuit in the datasheet, the TPS3779 is powered with the same voltage to be monitored (Vmon). However, is it possible to power the TPS3780 (which we are using instead of TPS3779) using fixed 1.8V instead of the Vmon (varying between 3.3V and 4.2V) for the three-resistor application of Early Warning Detection.

    I am doubting this because there might be a slight delay in generation of 1.8V (few mS). So there might be a small instance of time when the TPS3780 is not powered but voltage is available at the input pins. There is 2.2Meg external input resistance though. Please help.

    Thanks.

  • 0 in reply to Bhargav Jyoti Saikia
    TI__Genius 12630 points

    The voltage at VDD pin must be between 0V and 6.5V. The voltage at either SENSE pin must be between 0V and 6.5V. It doesn't matter which is higher or if one comes on before the other. Just respect the recommend operating condition specs found in Table 7.3 and the device will function properly.

    -Michael

  • 0 in reply to Michael_DeSando
    Intellectual 420 points

    Thanks Michael,

    That cleared a lot of doubts. Yes, the input voltages will not exceed 4.2V. Care has been taken about that.

    Thanks.