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SMD code MU 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.

Not sure which one you have?

Answer up to 4 quick questions and these 20 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • M1MA152WKSOT-23onsemiNot recordedonsemi
    What it is
    Not recorded
    Maker
    onsemi
    Package
    SOT-23
    Pins
    3
    Details
    dual diode cc 80V 100mA
    Source
    Published code list

    Is it dead? The meter test is below: Silicon diode.

  • M1MA152WKT1SOT-23onsemiNot recordedonsemi
    What it is
    Not recorded
    Maker
    onsemi
    Package
    SOT-23
    Pins
    3
    Source
    Published code list

    Is it dead? The meter test is below: This part.

  • PT7M6244NLTA3ESOT-23Voltage supervisor, Pericom TechnologyVoltage supervisorPericom Technology
    What it is
    Voltage supervisor
    Maker
    Pericom Technology
    Package
    SOT-23
    Pins
    3
    Details
    Voltage detector IC: 4.4V±1.5%, -Reset ODO, L-free
    Source
    Published code list

    Is it dead? The meter test is below: Integrated circuit.

  • RT9818D-35GVSOT-23Voltage supervisor, RichtekVoltage supervisorRichtek
    What it is
    Voltage supervisor
    Maker
    Richtek
    Package
    SOT-23
    Pins
    3
    Details
    Voltage Detector
    Source
    Published code list

    Is it dead? The meter test is below: Integrated circuit.

  • ZVN3320FSOT-23Not recordedNot recorded
    What it is
    Not recorded
    Maker
    Not recorded
    Package
    SOT-23
    Pins
    3
    Details
    n-ch mosfet 200V 60mA
    Source
    Published code list

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

  • 10 more parts have no package on record. Nothing rules them out, so they stay.
    • LFCN-1000+RF filter, Mini-CircuitsRF filterMini-Circuits
      What it is
      RF filter
      Maker
      Mini-Circuits
      Package
      Not recorded
      Pins
      Not recorded
      Details
      LTCC filter
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: This part.

    • NCP163AMX250LDO regulator, onsemiLDO regulatoronsemi
      What it is
      LDO regulator
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      LDO Regulator - Ultra-Low Noise, High PSRR, RF and Analog Circuits
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: Voltage regulator.

    • NCV8163AMX250LDO regulator, onsemiLDO regulatoronsemi
      What it is
      LDO regulator
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      LDO Regulator - Ultra-Low Noise, High PSRR, RF and Analog Circuits
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: Voltage regulator.

    • NCV8570MN250LDO regulator, onsemiLDO regulatoronsemi
      What it is
      LDO regulator
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      200 mA, Ultra Low Noise, High PSRR, BiCMOS RF LDO Regulator
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: Voltage regulator.

    • 74AUP2G3404FW3Diodes IncorporatedNot recordedDiodes Incorporated
      What it is
      Not recorded
      Maker
      Diodes Incorporated
      Package
      Not recorded
      Pins
      Not recorded
      Details
      CMOS logic IC: Inverting buffer with open-drain and inverter
      Source
      Published code list

      Is it dead? The meter test is below: Integrated circuit.

    • BD5238FVEVoltage supervisor, ROHMVoltage supervisorROHM
      What it is
      Voltage supervisor
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      CMOS-IC: Voltage Detector 3,8V, Reset Open drain output
      Source
      Published code list

      Is it dead? The meter test is below: Integrated circuit.

    • BD5238GVoltage supervisor, ROHMVoltage supervisorROHM
      What it is
      Voltage supervisor
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      CMOS-IC: Voltage Detector 3,8V, Reset Open drain output
      Source
      Published code list

      Is it dead? The meter test is below: Integrated circuit.

    • IXD5109N25ANVoltage supervisor, IXYSVoltage supervisorIXYS
      What it is
      Voltage supervisor
      Maker
      IXYS
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Voltage detector IC: 2.5V±2%, +Reset ODO
      Source
      Published code list

      Is it dead? The meter test is below: Integrated circuit.

    • IXD5127N46KNRVoltage supervisor, IXYSVoltage supervisorIXYS
      What it is
      Voltage supervisor
      Maker
      IXYS
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Voltage detector IC: 4.6V±0.8%, +Reset ODO, -MR, 800ms Rt delay
      Source
      Published code list

      Is it dead? The meter test is below: Integrated circuit.

    • R1118K241BRicohNot recordedRicoh
      What it is
      Not recorded
      Maker
      Ricoh
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Linear voltage regulator IC: 2.4V±1%, 150mA, +CE
      Source
      Published code list

      Is it dead? The meter test is below: Voltage regulator.

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.

Silicon diode

Diode range, part lifted or one leg off the pad. Red probe on the anode.

Working, it reads

About 0.5 to 0.8 V anode to cathode, and open the other way. Small switching diodes read about 0.6 to 0.7 V; large rectifiers can read a little lower.

Dead, it reads

  • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
  • Open both ways: failed open.
  • A reading the wrong way round as well: leaky.
On the board
this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
A three-pin body can hold two diodes. With a common pin they read two junctions from that pin, just like a transistor; in series they read two drops end to end. Test each pair the datasheet names.

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

This part

Diode range and ohms range, part lifted.

Working, it reads

Depends on what it is. The datasheet, or an identical part, says.

Dead, it reads

  • Between two pins, the same reading both ways, near 0 V with a continuous beep: shorted.
  • Open between every pair of pins: failed open, or a part that reads open when working.
On the board
this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.

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

Integrated circuit

Voltage with the board powered; ohms from each pin to ground with it off.

Working, it reads

Supply pin at its voltage and the output doing what the datasheet says. Readings between pins depend on the part.

Dead, it reads

  • A pin near 0 Ω to ground or to the supply pin where an identical part does not read that: failed short.
  • Supply present, output stuck: failed, or its load has.
On the board:
A pin shorted to ground on the board can be anything on that net. Lift the pin to be sure.
Compare:
The surest reference is the same IC on a working board, measured pin by pin.
Watch for:
Its protection diodes can read like junctions between pins, even like a transistor. That proves nothing either way.

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

N-channel MOSFET

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

Working, it reads

Red probe on the source, black on the drain: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.

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. Often all three pins end up shorted together.
  • No body diode at all: failed open.
On the board
the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. A drain short can be the load. 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.

Voltage regulator

Voltage, board powered, black probe on ground. Then ohms with the power off.

Working, it reads

Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

Dead, it reads

  • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
  • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
  • Power off, input to output near 0 Ω: shorted.
On the board:
An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
Compare:
The same regulator on another rail or another board shows the right voltages and the right resistances.
Watch for:
Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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 MU

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

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