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LMV331: LMV331IDBV

James Liu2
Prodigy 50 points
Part Number: LMV331
Other Parts Discussed in Thread: LMV7275, TLV1701

Hello,

I have question to ask about LMV331
The circuit design is as follows

When V+ > V-, Vo = VCC
When V+ < V-, Vo = GND

But an abnormal phenomenon occurs, when V+ < V-, Vo = VCC


Test 14pcs, normal 7pcs, abnormal 7pcs

Is there a problem with the design?
thanks

  • +1
    Guru 297030 points

    The LMV331 does not have rail-to-rail inputs; the valid input common-mode range ends 0.8 V below the positive supply.

    Use another comparator like the TLV1701 or LMV7275.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 24850 points

    Thanks James for your post and Clemens for your support.

    As Clemens correctly noted, there is a problem with the circuit since the comparator does not have an input stage that is rail to rail.  One thing also worth pointing out is that in the case of a comparator, the common mode range applies to both inputs independently.  For the LMV331 to operate properly where the output reflects the input conditions, both inputs need to be a minimum of 0.8V below VCC.  In your use case of VCC = 3.3V, both inputs need to be less than 2.5V.

    Chuck

  • 0 in reply to Chuck Sins
    Prodigy 50 points

    I understand.

    I try TLV1701 for my issue.

    It can solve this issue.

    Thanks