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Original question:

TLV3401 open-drain pull-up voltage requirements

TLV3404: Not good for 1.8V low level?

Barry Klein
Prodigy 60 points
Part Number: TLV3404
Other Parts Discussed in Thread: TLV1851, , LM239

Looking at Figure 4, is this part generally a bad choice if the output pull-up voltage is 1.8V?

If so,what part would be recommended that would also be compatible with higher pull up voltages?

  • 0
    TI__Genius 11701 points

    Hi Barry,

    Thanks for reaching out. TLV3404 is fine for pulling up to 1.8V. Figure 4 just shows the output voltage when it is low (VOL), which is dependent on how much current is sinking through the pull up resistor.  With 1.8V pull up voltage and 4.5kohm pull up, then you would sink 0.4 mA and get a VOL of about 0.5V. If a smaller VOL is needed, then a larger pull up resistor is needed to sink less current. We have a new nanopower family of devices TLV1851/61 that has improved specs, however the quad channel has not released yet. 

  • 0 in reply to Chi Nguyen1
    Prodigy 60 points

    We intend to interface to a FPGA and I was concerned that it might be a weak signal for this.  I don't know enough about interfacing to fpga's....

  • 0 in reply to Barry Klein
    TI__Genius 11701 points

    Hi Barry,

    Can you tell me more about your application and what you are trying to accomplish? What are your inputs and supply voltages? TLV3404 is a nanopower comparator so it does not have a very strong drive capability as well as its response time would be slower as well with larger pull up resistances. Is speed a concern? 

  • 0 in reply to Chi Nguyen1
    Prodigy 60 points

    No speed is not a concern.  It might benefit from hysteresis though.  It is interfacing mechanical switches. The inputs have TVSD overvoltage protection and diode and series resistor to a voltage potential like +5V usually. Another part we have used is the LM239 which has a much higher open collector current like 4mA.

  • 0 in reply to Barry Klein
    TI__Genius 11701 points

    Yes LM239 does have stronger drive strength and can sink more current with lower VOL. The sinking current would be dependent the pull up voltage and pull up resistor.