SMD code UDs
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 UD was searched.
57 parts are printed UDs
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.
2SC3931-DSOT-3233 pins, PanNot recordedSOT-3233 pinsPan
- What it is
- Not recorded
- Maker
- Pan
- Package
- SOT-323
- Pins
- 3
- Details
- Si-npn: RF, FM/AM, 30V, 15mA, 150mW, B=100..260, 650MHz
- Source
- Published code list
Is it dead? The meter test is below: This part.
2SC4627-DSOT-4163 pins, PanNot recordedSOT-4163 pinsPan
- What it is
- Not recorded
- Maker
- Pan
- Package
- SOT-416
- Pins
- 3
- Details
- Si-npn: FM/AM RF, 30V, 15mA, 125mW, 650MHz, B=100..260
- Source
- Published code list
Is it dead? The meter test is below: This part.
3SK127SOT-143N-channel MOSFET, 4 pins, ToshibaN-channel MOSFETSOT-1434 pinsToshiba
- What it is
- N-channel MOSFET
- Maker
- Toshiba
- Package
- SOT-143
- Pins
- 4
- Details
- n-MOS-d: Dual-Gate, UHF, 15V, Idss>0mA, Up<1V
- Source
- Published code list
Is it dead? The meter test is below: N-channel MOSFET.
APE8865U5-18SOT-353LDO regulator, 5 pins, Advanced Power ElectronicsLDO regulatorSOT-3535 pinsAdvanced Power Electronics
- What it is
- LDO regulator
- Maker
- Advanced Power Electronics
- Package
- SOT-353
- Pins
- 5
- Details
- Linear voltage regulator IC: LDO, 1.8±2%, 300mA, +CE
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
AX6608-18A5SOT-353LDO regulator, 5 pins, AXElite TechnologyLDO regulatorSOT-3535 pinsAXElite Technology
- What it is
- LDO regulator
- Maker
- AXElite Technology
- Package
- SOT-353
- Pins
- 5
- Details
- Linear voltage regulator IC: LDO, 1.8V±2%, 300mA, +CE
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
AX6608-18BSOT-23-5LDO regulator, 5 pins, AXElite TechnologyLDO regulatorSOT-23-55 pinsAXElite Technology
- What it is
- LDO regulator
- Maker
- AXElite Technology
- Package
- SOT-23-5
- Pins
- 5
- Details
- Linear voltage regulator IC: LDO, 1.8V±2%, 300mA, +CE
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
AX6608-18Z6DFNLDO regulator, AXElite TechnologyLDO regulatorDFNNot recordedAXElite Technology
- What it is
- LDO regulator
- Maker
- AXElite Technology
- Package
- DFN
- Pins
- Not recorded
- Details
- Linear voltage regulator IC: LDO, 1.8V±2%, 300mA, +CE
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
BB504SOT-233 pins, InfineonNot recordedSOT-233 pinsInfineon
- What it is
- Not recorded
- Maker
- Infineon
- Package
- SOT-23
- Pins
- 3
- Details
- equivalent BB502
- Source
- Published code list
Is it dead? The meter test is below: This part.
BCR151TSOT-416Digital transistor (PNP, resistors built in), 3 pins, InfineonDigital transistor (PNP, resistors built in)SOT-4163 pinsInfineon
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- Infineon
- Package
- SOT-416
- Pins
- 3
- Details
- Si-pnp-Digi: Sw, 50V, 100mA, 250mW, R1/R2=100k/100k, 120MHz
- Source
- Published code list
Is it dead? The meter test is below: Digital transistor.
6 more parts have no package on record
2SC4973DNPN transistor, PanasonicNPN transistorNot recordedNot recordedPanasonic
- What it is
- NPN transistor
- Maker
- Panasonic
- Package
- Not recorded
- Pins
- Not recorded
- Details
- NPN transistor: HF, 20V, 15mA, 650MHz, B=120..260
- Source
- Published code list
Is it dead? The meter test is below: NPN transistor.
2SK1154 pins, ToshibaNot recordedNot recorded4 pinsToshiba
- What it is
- Not recorded
- Maker
- Toshiba
- Package
- Not recorded
- Pins
- 4
- Source
- Published code list
Is it dead? The meter test is below: This part.
AP7341D-32FS4-7LDO regulator, Diodes IncorporatedLDO regulatorNot recordedNot recordedDiodes Incorporated
- What it is
- LDO regulator
- Maker
- Diodes Incorporated
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Linear voltage regulator IC: LDO, 3.2V±1%, 300mA, +CE, CL
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
APE8865U4-18LDO regulator, Advanced Power ElectronicsLDO regulatorNot recordedNot recordedAdvanced Power Electronics
- What it is
- LDO regulator
- Maker
- Advanced Power Electronics
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Linear voltage regulator IC: LDO, 1.8±2%, 300mA, +CE
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
AX6608-18SCLDO regulator, AXElite TechnologyLDO regulatorNot recordedNot recordedAXElite Technology
- What it is
- LDO regulator
- Maker
- AXElite Technology
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Linear voltage regulator IC: LDO, 1.8V±2%, 300mA, +CE
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
BCR151L3Digital transistor (PNP, resistors built in), InfineonDigital transistor (PNP, resistors built in)Not recordedNot recordedInfineon
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- Infineon
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Si-pnp-Digi: Sw, 50V, 100mA, 250mW, R1/R2=100k/100k, 120MHz
- Source
- Published code list
Is it dead? The meter test is below: Digital transistor.
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.
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.
NPN transistor
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
- 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.
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.
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.
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