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TMP390: Output configuration and need for pull-up resistors

franziskus
Expert 8479 points
Part Number: TMP390


Tool/software:

Hi,

The TMP390 has two outputs (OUTA and OUTB). The data sheet specifies them as open-drain active low outputs, but there are no resistance values specified for the open state.
Is it possible to connect both outputs together without any pull-up resistor to disable e.g. a connected IC.
The desired function should be the following: if one of the two outputs is activated (low) the connected IC will be deactivated by grounding it’s Enable Input.
Or is there a special need for a pull-up resistor?

Is there a block diagram of the TMP390 you can share?

Best regards

  • 0
    TI__Genius 12865 points

    Franziskus,

    I would not tie both OUTA & OUTB together, and since they are open drain outputs, they need a pull-up resistor if used. If you only want to use one channel, just connect the undesired output to GND. The datasheet says there is a minimum of 1KOhm for the pull up resistors on OUTA & OUTB. Below is an example schematic from the EVM where 10KOHm pull-ups are used:

    Regards

    -Alex Thompson

  • 0 in reply to Alex Thompson
    TI__Expert 8479 points

    Thanks Alex, however, that does not help.

    --------------------

    I would like to know, if it’s forbidden to connect both outputs together or if it’s allowed. I know that somewhere in the circuit a pull-up resistor > 1kOhm is necessary.

    And a block diagram would be very helpful.

    --------------------

    Best regards

  • 0 in reply to franziskus
    TI__Genius 12865 points

    Franziskus,

    I apologize for the confusion, I was mistaken about connecting the open drain outputs together. That is allowed, although I don't have a block diagram to share at this time. Setting the OUTA & OUTB with different resistors and connecting them together will allow you to create a window comparator. Again I am sorry for the confusion, the datasheet should explicitly say this is allowed.

    Regards

    Alex Thompson