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LM317: detail specification

Yen Ting Chu
Intellectual 1350 points
Part Number: LM317

Dear Team,

May I know if the following spec for LM317 is available? I see it is not shown in the datasheet. Thanks.

1. Dropout Voltage vs Output Current

2. Quiescent Current

Best regards,

Andy Chu

  • 0
    Guru 140200 points
    Hi Yen,

    have a look at figure 4 of datasheet of LM317-N to see the dropout voltage versus output current performance.

    The LM317 does not have a quiescent current in the usual sense. There's a minimum load current which must flow to maintain regulation. This is well explained in section 8.1 of datasheet of LM317-N.

    Kai
  • 0 in reply to kai klaas69
    TI__Intellectual 1350 points
    Hi Kai,

    So there is no specification for quiescent current spec for LM317?

    Andy
  • 0 in reply to Yen Ting Chu
    TI__Mastermind 23361 points
    Hi Andy,

    LM317 is an old design, it's a regulator only. It's not even a low drop output regulator (LDO). As you can notice in the datasheet, the minimum Vin - Vout needs to be at least 3V. That's why we don't care the dropout since you need to have 3V minimum margin.

    For the quiescent spec, this device does require to have 3.5mA minimum load. It cannot regulate without load. Quiescent current is usually defined and speced at zero or small load. It's not applied to the case of LM317.

    Regards,
    Jason Song