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LMV7272: LMV7272 Max Input Current

Conrad Farnsworth
Prodigy 80 points
Part Number: LMV7272
Other Parts Discussed in Thread: OPA340

Hello, 

What are the rail clamping diodes rated for on the LMV7272 comparator? I need to size a resistor for current limiting to protect the IC when power is off. 

Thanks!

  • +1
    TI__Guru 52756 points

    Hello Conrad,

    Generally, we say Abs Max of 10mA, and recommend keeping the current below 1mA (the less the better).

    If this condition occurs as part of normal operation, external Schottky clamp diodes should be used.

  • 0 in reply to Paul Grohe
    Prodigy 80 points

    Thank you for the quick reply!

    I have a couple follow-up questions!

    1) The datasheet seems to suggest 100mVf protection diodes. Best a guy can do with Schottky clamps is ~200mV. Are 200mVf diodes sufficient? 

    2) This 10mA (abs max) value is relevant for the BGA package version of this amplifier?

    3) Slightly off topic: Why do some of your products have published max currents and others don't? For example this product does not have the abs max input current published but your OPA340 has a nice little note about current-limiting the input pins to 10mA. 

    Thanks!

    -Conrad

  • 0 in reply to Conrad Farnsworth
    TI__Genius 12940 points

    Hello Conrad,

    I would recommend that you use the TLV7012DSGR. The inputs to this device are diode clamped to Vee and the device comes in a WSON (2 × 2 mm2) package that is slightly larger. This device also encourages the 10mA current limiting that you just mentioned. It would save you the hassle of external diodes.

    Kind Regards,

    Joe

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (www.ti.com/.../important-notice.shtml)

  • 0 in reply to Conrad Farnsworth
    TI__Guru 52756 points

    Hi Conrad,

    1.) The internal ESD "diodes" look like a conventional P-N diode (~700mV Vf). They really start to conduct about 500mV. Schottky's are recommended so that the external diode starts to conduct before the internal diode. The LMV7272 100mV Abs Max is very conservative.

    2.) Yes.

    3.)  Depends on the team releasing the datasheet at the time. The problem is that because it is a diode, to get 10mA, you will have to severely violate the maximum voltage spec. If we only put the max current, then we encourage violating the max votlage. If we only put the votlage, then we get questions such as yours asking about the max current. Most of the newer datasheets will have both with a table note or Apps section note.