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SMD marking

85in 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.

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.

  • TSM850N06CXSOT-23MOSFET, 3 pins, Taiwan Semiconductor
    What it is
    MOSFET
    Maker
    Taiwan Semiconductor
    Package
    SOT-23
    Pins
    3
    Source
    From the manufacturer's datasheet

    Is it dead?

    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:
    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.

  • 1 more part has no package on record. Nothing rules them out, so they stay.
    • BAT68-05Schottky diode, Infineon
      What it is
      Schottky diode
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      Is it dead?

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

      Working, it reads

      About 0.15 to 0.45 V anode to cathode, roughly half a silicon diode, and open the other way.

      Dead, it reads

      • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
      • A reading the wrong way round as well: leaky.
      • Open both ways: failed open.
      On the board:
      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 large Schottky can read about 0.1 V forward and beep like a short, and leaks a little the wrong way when good, more when warm. It is shorted only if it reads the same both ways. Measure it cold, beside an identical cold one.

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

11 more parts are printed with a code easy to misread as 85

Printed with a code easy to misread

One character differs, and it is one that is easy to confuse under a lamp. The odd one out is marked on each.

  • 2SC2412Kprinted BSSOT-23NPN transistor, 3 pins, JSCJ

    Printed BS on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

    What it is
    NPN transistor
    Maker
    JSCJ
    Package
    SOT-23
    Pins
    3
    Details
    Bipolar transistor, NPN, 50 V, 0.15 A
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted or its base leg off the pad.

    Working, it reads

    Red probe on the base reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
    • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
    • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
    • A reading the wrong way round, where it should be open: leaky.
    On the board:
    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 pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

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

  • AO3435printed B5SOT-23P-channel MOSFET, 3 pins, Alpha & Omega Semiconductor

    Printed B5 on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

    What it is
    P-channel MOSFET
    Maker
    Alpha & Omega Semiconductor
    Package
    SOT-23
    Pins
    3
    Details
    P-channel MOSFET (8-60 V)
    Source
    From the manufacturer's datasheet

    Is it dead?

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

    Working, it reads

    Red probe on the drain, black on the source: 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:
    On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.

  • AO3435Lprinted B5SOT-23P-channel MOSFET, 3 pins, Alpha & Omega Semiconductor

    Printed B5 on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

    What it is
    P-channel MOSFET
    Maker
    Alpha & Omega Semiconductor
    Package
    SOT-23
    Pins
    3
    Details
    P-channel MOSFET (8-60 V)
    Source
    From the manufacturer's datasheet

    Is it dead?

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

    Working, it reads

    Red probe on the drain, black on the source: 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:
    On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.

  • AO3453printed BSSOT-23P-channel MOSFET, 3 pins, Alpha & Omega Semiconductor

    Printed BS on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

    What it is
    P-channel MOSFET
    Maker
    Alpha & Omega Semiconductor
    Package
    SOT-23
    Pins
    3
    Details
    P-channel MOSFET (8-60 V)
    Source
    From the manufacturer's datasheet

    Is it dead?

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

    Working, it reads

    Red probe on the drain, black on the source: 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:
    On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.

  • BZX84-C47printed B5SOT-23Zener diode, 3 pins, Nexperia

    Printed B5 on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Nexperia
    Package
    SOT-23
    Pins
    3
    Details
    47 V approx. ±5% voltage regulator (Zener) diode
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.

    Working, it reads

    About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.

    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, forward too: failed open.
    • Holds well off its rated voltage on the supply test: drifted.
    • A soft knee, or a voltage that creeps on the supply test: leaky.
    On the board:
    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 meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.

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

  • 6 more parts have no package on record. Nothing rules them out, so they stay.
    • BBY58-05Wprinted B5Infineon

      Printed B5 on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

      What it is
      Not recorded
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      Is it dead?

      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:
      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.

    • BGA615L7printed BSRF amplifier (MMIC), Infineon

      Printed BS on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

      What it is
      RF amplifier (MMIC)
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      Is it dead?

      Voltage, board powered, on the output pin that the bias resistor or choke feeds.

      Working, it reads

      The output pin sits at the device voltage the datasheet gives, a few volts, below the supply.

      Dead, it reads

      • Output pin at 0 V, or near 0 Ω to ground with the power off: shorted inside.
      • Output pin at the full supply voltage: open inside, no current flowing.
      On the board:
      Measured on the board with power on; the bias network is part of the reading.
      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 figures depend on the part and its bias resistor. 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.

    • BSS670S2Lprinted BSsN-channel MOSFET, Infineon

      Printed BSs on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

      What it is
      N-channel MOSFET
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Small Signal MOSFET 55 V in SOT-23 package
      Source
      From the manufacturer's datasheet

      Is it dead?

      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:
      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.

    • BZX884B62Lprinted BSZener diode, Vishay

      Printed BS on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Vishay
      Package
      Not recorded
      Pins
      Not recorded
      Details
      62 V Zener diode
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.

      Working, it reads

      About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.

      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, forward too: failed open.
      • Holds well off its rated voltage on the supply test: drifted.
      • A soft knee, or a voltage that creeps on the supply test: leaky.
      On the board:
      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 meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.

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

    • SDB160WSprinted BSSchottky diode, Diotec

      Printed BS on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

      What it is
      Schottky diode
      Maker
      Diotec
      Package
      Not recorded
      Pins
      Not recorded
      Details
      SMD Schottky Barrier Rectifier Diodes
      Source
      From the manufacturer's datasheet

      Is it dead?

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

      Working, it reads

      About 0.15 to 0.45 V anode to cathode, roughly half a silicon diode, and open the other way.

      Dead, it reads

      • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
      • A reading the wrong way round as well: leaky.
      • Open both ways: failed open.
      On the board:
      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 large Schottky can read about 0.1 V forward and beep like a short, and leaks a little the wrong way when good, more when warm. It is shorted only if it reads the same both ways. Measure it cold, beside an identical cold one.

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

    • TLV75519PDQNprinted B5LDO regulator, 4 pins, Texas Instruments

      Printed B5 on the part. Easy to misread as 85. Check that character with a loupe before you order anything.

      What it is
      LDO regulator
      Maker
      Texas Instruments
      Package
      Not recorded
      Pins
      4
      Details
      500mA, Low-IQ, Small-Size, Low-Dropout Regulator
      Source
      From the manufacturer's datasheet

      Is it dead?

      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.

8 more parts have codes that begin with 85

Codes that begin with 85

For a marking with its end worn or burnt off. Each one shows its full printed code.

  • MMBTA55printed B55SOT-23PNP transistor, 3 pins, Panjit

    Printed B55. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    PNP transistor
    Maker
    Panjit
    Package
    SOT-23
    Pins
    3
    Details
    Bipolar transistor, PNP
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted or its base leg off the pad.

    Working, it reads

    Black probe on the base reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
    • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
    • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
    • A reading the wrong way round, where it should be open: leaky.
    On the board:
    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 pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

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

  • MMBTA55-AUprinted B55SOT-23Transistor, 3 pins, Panjit

    Printed B55. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Transistor
    Maker
    Panjit
    Package
    SOT-23
    Pins
    3
    Details
    Bipolar transistor
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted or its base leg off the pad.

    Working, it reads

    From the base, one probe colour reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
    • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
    • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
    • A reading the wrong way round, where it should be open: leaky.
    On the board:
    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 pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

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

  • MMBTA56printed B56SOT-23Transistor, 3 pins, Panjit

    Printed B56. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Transistor
    Maker
    Panjit
    Package
    SOT-23
    Pins
    3
    Details
    SMD General Purpose PNP Transistors
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted or its base leg off the pad.

    Working, it reads

    From the base, one probe colour reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
    • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
    • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
    • A reading the wrong way round, where it should be open: leaky.
    On the board:
    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 pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

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

  • MMBTA56-AUprinted B56SOT-23Transistor, 3 pins, Panjit

    Printed B56. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Transistor
    Maker
    Panjit
    Package
    SOT-23
    Pins
    3
    Details
    Bipolar transistor
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted or its base leg off the pad.

    Working, it reads

    From the base, one probe colour reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
    • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
    • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
    • A reading the wrong way round, where it should be open: leaky.
    On the board:
    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 pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

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

  • 4 more parts have no package on record. Nothing rules them out, so they stay.
    • AOZ13987DI-01printed BS01Load switch, Alpha & Omega Semiconductor

      Printed BS01. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

      What it is
      Load switch
      Maker
      Alpha & Omega Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      USB Type-C protection switch
      Source
      From the manufacturer's datasheet

      Is it dead?

      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.

    • AOZ13987DI-02printed BS02Load switch, Alpha & Omega Semiconductor

      Printed BS02. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

      What it is
      Load switch
      Maker
      Alpha & Omega Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      USB Type-C protection switch
      Source
      From the manufacturer's datasheet

      Is it dead?

      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.

    • AOZ13987DI-03printed BS03Load switch, Alpha & Omega Semiconductor

      Printed BS03. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

      What it is
      Load switch
      Maker
      Alpha & Omega Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      USB Type-C protection switch
      Source
      From the manufacturer's datasheet

      Is it dead?

      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.

    • AOZ13987DI-04printed BS04Load switch, Alpha & Omega Semiconductor

      Printed BS04. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

      What it is
      Load switch
      Maker
      Alpha & Omega Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      USB Type-C protection switch
      Source
      From the manufacturer's datasheet

      Is it dead?

      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.

Open this in the search to correct a character or try another package.