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LM339: LM339 response time range

Shu-Cheng LIN
Guru 11785 points
Part Number: LM339
Other Parts Discussed in Thread: TLV1704

Hi Sirs,

Sorry to bother you.

Our response time need a micro level, but if use 13k/3.57k on R5264/R5265, there will be 295ms.

If use 13k/3.24k on R5264/R5265, there will be 200us. It's ok for us but this resistor didn't match for our end customer.


So, We would like to know how much difference between the positive and negative voltages of the comparator will affect the reaction time?

Thanks!!

  • 0
    Guru 140200 points

    Hi Shu,

    the common mode input voltage range of LM339 is 0V...Vcc-1.5V. Exceeding this range makes the LM339 slow down and behave unexpectedly.

    Kai

  • 0
    TI__Guru 53846 points
    Hello Shu-Cheng,

    As Kai said, the input common mode range is being violated.

    The maximum input voltage at room temp is 1.5V below V+, or +1.8V on a 3.3V supply.

    The reference voltage is +2.5V, which is beyond the 1.8V limit. Several specifications, such as offset voltage and propagation delay will deteriorate.

    Try replacing the LM339 with a TLV1704, or change the threshold to < 1.3V.