This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM393: replacement

Part Number: LM393
Other Parts Discussed in Thread: LM2903, TLV1702-Q1

Hi Team,

I am currently using the LM393AD on a split power super +-12 and I have just noticed this part only works in temperature range 0C -to 70C.  I am now looking for a new comparator, and I have seen the LM2903M that operates between -45C to 80C.  Would this be considered a good replacement or would another part be recommend?

Look forward to your reply.

RocketMan46

  • The LM2903 is a higher-temperature variant of the LM393; that's why it is described in the same datasheet.

    Anyway, just plug your requirements (dual, open collector, 24 V, 80 °C) into the search function to see which devices would match. (The LM2903 is the cheapest …)

  • Hi,

    Thanks for your reply.

    I am a little weak on comparators but i think i have spotted a problem.

    If the LM2903 is powered by +-12V, and the input into the comparator swings between -12V to +12V. Does this therefore mean the comparator is out of its common mode range. The datasheet quotes "Operation from dual supplies also is possible as long as the difference between the two supplies is 2 V to 36 V, and VCC is at least 1.5 V more positive than the input common-mode voltage". Does this mean i should select a rail-rail comparator like the TLV1702-Q1?

    Thanks,

    Rocketman46
  • Both the LM393 and the LM2903 require that the inputs are more than two diode drops below the positive supply:

    If your input voltages are higher, then you must indeed use a comparator with rail-to-rail inputs. (And then your old circuit did not work either.)

    (And why are you asking for automotive rating? Sort by price.)

  • Hi,

    Thanks for your reply.

    Just to confirm my misunderstanding, searching on Farnell and RS sometimes the search can be misleading.

    Can you just confirm the below chips are the same function and can run from +-12V and are rail-rail, but one is automotive spec and the second is standard spec.

    * TLV1702AQDGKRQ1 - Automotive

    * TLV1702AIDGKR - Standard

    Thanks,

    RocketMan46

  • Yes, "I"/"Q" is the same temperature range, and "Q1" means automotive.
  • Hi Team,

    Can I just confirm I am reading the datasheet correctly and the below logic is correct?

    * (Vin- > Vin+) then Vout pulled high

    * (Vin- < Vin+) then Vout powered low

    Thanks,

    Rocketman46

  • No, when the positive input is more positive, the output is positive.

    Where did you read that in the datasheet?