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SMD code U22 in SMB

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 SMB is printed U22

Not sure which one you have?

Answer up to 4 quick questions and these 3 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • STTH212USMBRectifier, 2 pins, STMicroelectronicsRectifier2 pinsSTMicroelectronics
    What it is
    Rectifier
    Maker
    STMicroelectronics
    Package
    SMB
    Pins
    2
    Source
    Manufacturer datasheet

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

    Datasheetfor STTH212U, opens in a new tab
  • 2 more parts have no package on record. Nothing rules them out, so they stay.
    • 2SC4185RenesasNot recordedNot recordedRenesas
      What it is
      Not recorded
      Maker
      Renesas
      Package
      Not recorded
      Pins
      Not recorded
      Details
      npn RF 10V fT2.4GHz hFE 40-80
      Source
      Published code list

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

    • QS6U22P-channel MOSFETP-channel MOSFETNot recordedNot recorded
      What it is
      P-channel MOSFET
      Maker
      Not recorded
      Package
      Not recorded
      Pins
      Not recorded
      Details
      P-Channel MOSFET + Schottky Barrier Diode
      Source
      Published code list

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

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.

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.

Printed with a code easy to misread as U22

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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