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LMV339: LMV339 Output status when only IN- is out of common mode range

Sopatopa
Intellectual 470 points
Part Number: LMV339
Other Parts Discussed in Thread: TLV1704, LM2901, LM339, , TLV1701

Hello,

My customer uses the LMV339, the state of IN- and IN+ is below.

IN- is out of common mode voltage range.(about 4.7V)

IN+ is the common mode voltage range.(about 2.5V)

Vcc is 5V.

There is no explanation in the data sheet.(9.2.2.1 Input Voltage Range)

> Is there any problem using it?

> What is the state of the output? Low?

Regards

Sopatopa

  • 0
    TI__Mastermind 49766 points
    Hello Sopatopa,

    The output is not specified when either of the inputs is outside the common mode range.

    The output will probably be correct, but it can "flip" at any time if there are changes in temperature or supply voltage and would be unreliable.

    Ideally it should be replaced with a rail-to-rail input device, such as the TLV1704, for proper operation under that condition.

    Will this condition occur during normal operation? Or as part of an occasional error condition?

    It is also possible to use the older LM339 (or LM2901 if you need the same temp range), which should still work correctly, but it would be operated outside of specified input conditions and is not guaranteed (you take the risk - but it may be suitable for a one-time error). See section 9.2.2.1 of the LM339 datasheet. The legal input range of the LM339 would be 0 to 3.5V on a 5V supply.
  • 0 in reply to Paul Grohe
    Intellectual 470 points
    Hello Paul,
    Thank you for your fast reply.
    Currently, customer design the curcuite in progress, so we can not confirm the operation.
    I would like to consider R2R products as well.

    Regards.
    Sopatopa
  • 0 in reply to Sopatopa
    Intellectual 470 points
    Hello paul,

    I found my mistake.
    The data sheet has the following description.
    9.2.2.1 Input Voltage Range
    2. When IN- is higher than common mode and IN+ is within common mode, the output is low and the output
    transistor is sinking current.
    This explanation is consistent with the following conditions.
    > IN- is out of common mode voltage range.(about 4.7V)
    > IN+ is the common mode voltage range.(about 2.5V)
    > Vcc is 5V
    In the explanation of 2, it says that it becomes LOW as a function, is not it a guaranteed value?
    Are the conditions 1, 3 and 4 not guaranteed?

    Regards,
    Sopatopa
  • 0 in reply to Sopatopa
    TI__Mastermind 49766 points

    Hello Sopatopa,

    If the IN- (negative) input is above the IN+ (positive) input, then the output will be low (output sinking to GND). If the positive input is higher than the negative input, the output will be high (output transistor NOT sinking, output pulled high by pull-up resistor).

    So in your conditions above, yes, the output should be low.

    It seems you are confusing the LM339 (30V max) and the LMV339 (5V max).  Even though they have the same pinput and function - THEY ARE DIFFERENT DEVICES and behave differently when operated outside of specifications.

    The section 9.2.2.1 you are referring to is for the LM339. The LM339 has a unique ability to maintain the proper output if one input is still within common mode range. This is what section 9.2.2.1 is referring. This does not apply to the LMV339.

    The LMV339 does NOT have this ability - and will not have a defined output if any input is outside the common mode range.

    ANY OPERATION outside of any specified limits are not guaranteed.

    That is why it is better to use the R-R input TLV1701 to assure proper operation.

  • 0 in reply to Paul Grohe
    Intellectual 470 points

    Hello Paul,


    Thank you for your reply.

    I referred to the following data sheet.

    SLCS136T –AUGUST 1999–REVISED JANUARY 2015

    www.tij.co.jp/.../lmv339.pdf

    In this data sheet, 9.2.2.1 Input Voltage Range is described.

    Is it wrong that referred datasheet?

    Regards,

    sopatopa