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SMD code TQ in SOT-416

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 8 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • BAS40TCGPSOT-416Schottky diode, 3 pins, ChenmkoSchottky diode3 pinsChenmko
    What it is
    Schottky diode
    Maker
    Chenmko
    Package
    SOT-416
    Pins
    3
    Details
    SCHOTTKY DIODE, 40 V, 0.2 A
    Source
    Manufacturer datasheet

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

  • 2SA1989-QSOT-4163 pins, MitNot recorded3 pinsMit
    What it is
    Not recorded
    Maker
    Mit
    Package
    SOT-416
    Pins
    3
    Details
    Si-pnp: AF, 50V, 100mA, 150mW, B=120..270, 200MHz
    Source
    Published code list

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

  • 6 more parts have no package on record. Nothing rules them out, so they stay.
    • RTQ025P02HZGP-channel MOSFET, ROHMP-channel MOSFETNot recordedROHM
      What it is
      P-channel MOSFET
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Pch -20V -2.5A Small Signal MOSFET
      Source
      Manufacturer datasheet

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

    • 2SA1530APNP transistorPNP transistorNot recordedNot recorded
      What it is
      PNP transistor
      Maker
      Not recorded
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Published code list

      Is it dead? The meter test is below: PNP transistor.

    • BD45245GVoltage supervisor, ROHMVoltage supervisorNot recordedROHM
      What it is
      Voltage supervisor
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      CMOS-IC: Voltage Detector 2,4V, -Reset Open drain output, 500ms
      Source
      Published code list

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

    • RTQ025P02P-channel MOSFETP-channel MOSFETNot recordedNot recorded
      What it is
      P-channel MOSFET
      Maker
      Not recorded
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Published code list

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

    • uPA1901TEN-channel MOSFET, NEC ElectronicsN-channel MOSFETNot recordedNEC Electronics
      What it is
      N-channel MOSFET
      Maker
      NEC Electronics
      Package
      Not recorded
      Pins
      Not recorded
      Details
      MOSFET n-type: V-MOS, LogL, 30V, ±6.5A, 200mW, <45m(3A)
      Source
      Published code list

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

    • µPA1901TE6 pins, RenesasNot recorded6 pinsRenesas
      What it is
      Not recorded
      Maker
      Renesas
      Package
      Not recorded
      Pins
      6
      Source
      Published code list

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

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.

Schottky diode

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
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.

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.

P-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 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
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.

PNP transistor

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
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.

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.

Printed with a code easy to misread as TQ

One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.

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