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TLC372: Input common mode range requirements for the TLC372

Carlos Silva85
Expert 4915 points
Part Number: TLC372

I'm looking for clarification as to the input common mode range requirements for the TLC372

My circuit drives a TLC372 comparator circuit through a voltage divider to output a change of state when a threshold level is reached. One input to the comparator is from a precision 2.5V reference.

Datasheet states Vdd – 1.5V  – some comparators state both inputs must comply, others that only one input must comply, but this is not clear on the TLC372.

If I’m using a 3V3 single sided supply then the ICM range is only 1.8V, and as I’ve got a 2.5V reference at one input and resistor divided input that may be as high as 7V at the other, I'm concerned the common mode requirement could be violated. Can I have some feedback regarding this matter?

  • 0
    TI__Mastermind 24330 points

    Sorry Carlos

    the TLC372 is different than the other devices you are describing where only one input pin needs to be in the recommended input common mode range.  the TLC372 is a CMOS device and the common mode voltage range needs to adhered to.  So what you have described will not work and should not be recommended.  there will be some variation in the threshold of the input transistor, so do not get fooled if the part you are experimenting with works closer to the rail than the 1.5V requirement.

    the best solution would be to use a lower voltage reference or you could use a resistor divider at the output of your reference.  the input to the comparator is high impedance and the input bias is quite low.  So a simple resistor divider should do the trick.  it burns a little power and introduces a little bit of error due to the resistor error but this is would create a working solution for you.

    Chuck