SMD code ABs
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.
The last letter, s, is lower case, which on NXP and Philips parts is a date or factory code, so it was set aside and AB was searched.
151 parts are printed ABs
Not sure which one you have?
Answer up to 4 quick questions and these 50 parts are ranked, with a meter test that settles it. It works on a dead part too.
GSESLC12VD323S-2BSOD-323ESD protection diode, 2 pins, Good-ArkESD protection diodeSOD-3232 pinsGood-Ark
- What it is
- ESD protection diode
- Maker
- Good-Ark
- Package
- SOD-323
- Pins
- 2
- Details
- ESD protection diode, VRWM 12 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
JEB12CSOD-323TVS diode, 2 pins, JieJieTVS diodeSOD-3232 pinsJieJie
- What it is
- TVS diode
- Maker
- JieJie
- Package
- SOD-323
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
JEB12C-AUSOD-323TVS diode, 2 pins, JieJieTVS diodeSOD-3232 pinsJieJie
- What it is
- TVS diode
- Maker
- JieJie
- Package
- SOD-323
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
KDZVTF2.0BSOD-123FZener diode, 2 pins, ROHMZener diodeSOD-123F2 pinsROHM
- What it is
- Zener diode
- Maker
- ROHM
- Package
- SOD-123F
- Pins
- 2
- Details
- Zener Diode (AEC-Q101 qualified)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
LD39020ADTPU27RDFNLDO regulator, STMicroelectronicsLDO regulatorDFNNot recordedSTMicroelectronics
- What it is
- LDO regulator
- Maker
- STMicroelectronics
- Package
- DFN
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Voltage regulator.
LESD8LH5.0CN3T5GSOT-883ESD protection diode, 3 pins, LRCESD protection diodeSOT-8833 pinsLRC
- What it is
- ESD protection diode
- Maker
- LRC
- Package
- SOT-883
- Pins
- 3
- Details
- ESD protection diode, VRWM 5 V, IR @VRWM 1 μA, VBR Min 5.5 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
MMBD4448HTSSOT-523Switching diode, 3 pins, Galaxy MicroelectronicsSwitching diodeSOT-5233 pinsGalaxy Microelectronics
- What it is
- Switching diode
- Maker
- Galaxy Microelectronics
- Package
- SOT-523
- Pins
- 3
- Details
- 0.25A, 85V, Surface Mount Small Signal Switching Diodes
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
MMBD4448HTS-HFSOT-523Switching diode, 3 pins, ComchipSwitching diodeSOT-5233 pinsComchip
- What it is
- Switching diode
- Maker
- Comchip
- Package
- SOT-523
- Pins
- 3
- Details
- 85 V, 250 mA switching diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
MMBZ5226BSOT-23Zener diode, 3 pins, Formosa MicrosemiZener diodeSOT-233 pinsFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
MMDT5111WSOT-323Digital transistor (resistors built in), 3 pins, DiotecDigital transistor (resistors built in)SOT-3233 pinsDiotec
- What it is
- Digital transistor (resistors built in)
- Maker
- Diotec
- Package
- SOT-323
- Pins
- 3
- Details
- SMD Digital PNP Transistors
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
NX3008PBKVSOT-563Dual P-channel MOSFET, 6 pins, NexperiaDual P-channel MOSFETSOT-5636 pinsNexperia
- What it is
- Dual P-channel MOSFET
- Maker
- Nexperia
- Package
- SOT-563
- Pins
- 6
- Details
- 30 V, 220 mA dual P-channel Trench MOSFET
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: P-channel MOSFET pair.
4 more parts have no package on record
KCR405TTransistor, KECTransistorNot recordedNot recordedKEC
- What it is
- Transistor
- Maker
- KEC
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Bipolar transistor.
KRA352Digital transistor (PNP, resistors built in), KECDigital transistor (PNP, resistors built in)Not recordedNot recordedKEC
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- KEC
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
MMBT3906SLComplementary transistor pair (NPN and PNP), onsemiComplementary transistor pair (NPN and PNP)Not recordedNot recordedonsemi
- What it is
- Complementary transistor pair (NPN and PNP)
- Maker
- onsemi
- Package
- Not recorded
- Pins
- Not recorded
- Details
- PNP Epitaxial Silicon Transistor
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Bipolar transistor pair.
PBZ2.0BZener diode, ROHMZener diodeNot recordedNot recordedROHM
- What it is
- Zener diode
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
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.
TVS or ESD protection diode
Diode range, from the protected line to ground, part lifted if you can.
Working, it reads
A one-way part reads about 0.6 to 0.8 V forward and open in reverse. A two-way part reads open both ways. Arrays with several lines read as the datasheet's diagram draws them.
Dead, it reads
- From the line to ground, the same reading both ways, near 0 V with a continuous beep: shorted.
- A reading both ways on a one-way part: leaky.
- A one-way part open both ways: failed open.
- On the board
- , a line reading shorted to ground can be this part or anything else on that line. Lift it: if the short goes with it, it has failed.
- Compare:
- The same part on the next line or connector pin is the healthy reading to compare with.
- Watch for:
- A two-way part reads open both ways when it is good, exactly like one that has failed open. The meter cannot tell them apart; an identical part on the next line can.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Bipolar transistor
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
- 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.
Zener diode
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
- 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.
Digital transistor
Ohms range, part lifted. The datasheet gives the built-in resistors: R1 in series with the base, R2 from base to emitter.
Working, it reads
Base to emitter reads about R1 plus R2 either way round, about 20 kΩ on a 10 k and 10 k part, give or take their wide tolerance. Collector to emitter reads open. A part with no R2 reads a junction behind R1 one way instead.
Dead, it reads
- Collector to emitter the same both ways, near 0 Ω with a continuous beep: shorted.
- From the base, open or far above R1 plus R2: R1 has failed. Static damage shows here most often.
- Base to emitter near 0 Ω: failed short.
- 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:
- The readings depend on the resistor values, so an identical part elsewhere on the board is the surest reference. Measure it the same way.
- Watch for:
- On the diode range a good part with 10 kΩ resistors reads open on every pair, so a good part looks dead there. Use the ohms range.
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.
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.
Bipolar transistor pair
Diode range, part lifted. Test each transistor on its own pins, as the datasheet's pinout gives them.
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
- 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.
Digital transistor
Ohms range, part lifted. The datasheet gives the built-in resistors: R1 in series with the base, R2 from base to emitter.
Working, it reads
Base to emitter reads about R1 plus R2 either way round, about 20 kΩ on a 10 k and 10 k part, give or take their wide tolerance. Collector to emitter reads open. A part with no R2 reads a junction behind R1 one way instead.
Dead, it reads
- Collector to emitter the same both ways, near 0 Ω with a continuous beep: shorted.
- From the base, open or far above R1 plus R2: R1 has failed. Static damage shows here most often.
- Base to emitter near 0 Ω: failed short.
- 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:
- The readings depend on the resistor values, so an identical part elsewhere on the board is the surest reference. Measure it the same way.
- Watch for:
- On the diode range a good part with 10 kΩ resistors reads open on every pair, so a good part looks dead there. Use the ohms range.
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 pair
Diode range, part lifted. Test drain to source first, then short gate to source and test again. Test each MOSFET on its own pins, as the datasheet's pinout gives them.
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.
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