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LM140QML: Quiescent current for LM140H-12/883

Chris Cooper
Prodigy 50 points
Part Number: LM140QML


If I’m understanding this part, a NPN linear regulator, the Iq current should be some gain factor of the current to the load. Thus as the current to the load increases the Iq current should increase. Upon testing a part made per MIL-M-38510/10703BX, just the opposite happens. Iscd decreases based on the load current increasing. This Mil spec lists the LM140 as a generic PN to this specification. TI is not listed on the QML for this part. I would like to know how this part reacts in the circuit to see if it would work in my existing circuit.

  • 0
    TI__Genius 17125 points
    Hello Chris,

    Iq is the current needed to power the circuit. It is also called ground current. It is typically tested in our test systems by placing an ammeter between the ground pin and ground, although it can also be measured by subtracting the load current from the input current. To get an accurate reading from the method of testing, the ammeters need to be right at the pins to be sure all current is being measured and that current to external circuits is not being ignored.

    Iq is an absolute, measured value. It is not a ratio or gain calculation. Iq will increase with increasing load current.

    The LM140QML from Texas Instruments is essentially the same product as the MIL-M-38510/10703BX supplied by National Semiconductor. National stopped supplying the LM140 per MIL-PRF-38510 and that slash sheet, but switched over to meeting Q class requirements of MIL-PRF-38535. While the part is the same, some of the test conditions may have changed. Also, the part has been transferred to a newer wafer fab. TI bought National in 2011, but the part is still manufactured in the old National fab.