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SMD code 5409 in SOT-23

Marking codes are not standardised, and the same code is reused by unrelated makers for unrelated parts. Below is every part in our tables printed with it, and any printed with a code that is easy to misread as it, from the manufacturers' own marking tables and published code lists.

1 part in SOT-23 is printed 5409

Not sure which one you have?

Answer up to 4 quick questions and these 2 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • SMG5409-CSOT-23MOSFET, 3 pins, SeCoSMOSFET3 pinsSeCoS
    What it is
    MOSFET
    Maker
    SeCoS
    Package
    SOT-23
    Pins
    3
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: MOSFET.

    Datasheetfor SMG5409-C, opens in a new tab
  • 1 more part has no package on record. Nothing rules it out, so it stays.
    • G5409AS1ULoad switch, 12 pins, Global Mixed-mode TechnologyLoad switch12 pinsGlobal Mixed-mode Technology
      What it is
      Load switch
      Maker
      Global Mixed-mode Technology
      Package
      Not recorded
      Pins
      12
      Details
      5.5V, 7A Low RDSON Load Switch
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: Load switch.

      Datasheetfor G5409AS1U, opens in a new tab

Is it dead? One meter test per kind

Parts of the same kind are tested the same way, so each test is here once. Each part above points to its own.

MOSFET

Diode range, part lifted. Test drain to source first, then short gate to source and test again.

Working, it reads

One way between drain and source reads about 0.4 to 0.9 V, the body diode, and the other way open. The gate reads open to both other pins.

Dead, it reads

  • Drain to source the same both ways, near 0 V with a continuous beep, and still so after shorting gate to source: shorted. The classic failure.
  • The gate reads low to source or drain: gate shorted.
  • No body diode at all: failed open.
On the board
the gate usually has a resistor to the source, which reads as that resistor and is not a fault. Lift a leg to be sure.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
The diode range can charge the gate enough to turn the part on, and then drain to source reads near 0 both ways on a good part. Short gate to source and test again before you condemn it.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

Load switch

Voltage, board powered, black probe on ground.

Working, it reads

Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

Dead, it reads

  • Output at the input voltage while switched off: the pass element has shorted.
  • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
On the board:
An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

Codes that begin with 5409

For a marking with its end worn or burnt off. Each code has a page of its own.

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