SMD code 18-
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.
157 parts are printed 18-
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.
PSD18-LF-T7SOD-3232 pins, UMWNot recordedSOD-3232 pinsUMW
- What it is
- Not recorded
- Maker
- UMW
- Package
- SOD-323
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: This part.
S-LM3Z33VPT1GSOD-323Zener diode, 2 pins, LRCZener diodeSOD-3232 pinsLRC
- What it is
- Zener diode
- Maker
- LRC
- Package
- SOD-323
- Pins
- 2
- Details
- Zener diode, VZ Min 31 V, VZ Nom 33 V, VZ Max 35 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
S-LM3Z33VT1GSOD-323Zener diode, 2 pins, LRCZener diodeSOD-3232 pinsLRC
- What it is
- Zener diode
- Maker
- LRC
- Package
- SOD-323
- Pins
- 2
- Details
- Zener diode, VZ Min 31 V, VZ Nom 33 V, VZ Max 35 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
S-LM5Z33VPT1GSOD-523Zener diode, 2 pins, LRCZener diodeSOD-5232 pinsLRC
- What it is
- Zener diode
- Maker
- LRC
- Package
- SOD-523
- Pins
- 2
- Details
- Zener diode, VZ Min 31 V, VZ Nom 33 V, VZ Max 35 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
S-LM5Z33VT1GSOD-523Zener diode, 2 pins, LRCZener diodeSOD-5232 pinsLRC
- What it is
- Zener diode
- Maker
- LRC
- Package
- SOD-523
- Pins
- 2
- Details
- Zener diode, VZ Min 31 V, VZ Nom 33 V, VZ Max 35 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
S-LM5Z33VT1G-SSOD-523Zener diode, 2 pins, LRCZener diodeSOD-5232 pinsLRC
- What it is
- Zener diode
- Maker
- LRC
- Package
- SOD-523
- Pins
- 2
- Details
- Zener diode, VZ Min 31 V, VZ Nom 33 V, VZ Max 35 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
S-LMBR180FT1GSOD-123FSchottky diode, 2 pins, LRCSchottky diodeSOD-123F2 pinsLRC
- What it is
- Schottky diode
- Maker
- LRC
- Package
- SOD-123F
- Pins
- 2
- Details
- Schottky diode, VR 80 V, IF 1 A, VF Max 0.85 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
SMA2EZ18D5SMAZener diode, 2 pins, HXYZener diodeSMA2 pinsHXY
- What it is
- Zener diode
- Maker
- HXY
- Package
- SMA
- Pins
- 2
- Details
- Zener diode, 24 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
SML4746SMAZener diode, 2 pins, VishayZener diodeSMA2 pinsVishay
- What it is
- Zener diode
- Maker
- Vishay
- Package
- SMA
- Pins
- 2
- Details
- 18 V Zener diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
SOD18ASOD-123TVS diode, 2 pins, WeEn SemiconductorsTVS diodeSOD-1232 pinsWeEn Semiconductors
- What it is
- TVS diode
- Maker
- WeEn Semiconductors
- Package
- SOD-123
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
TLV74018PDQNX2SONLDO regulator, 4 pins, Texas InstrumentsLDO regulatorX2SON4 pinsTexas Instruments
- What it is
- LDO regulator
- Maker
- Texas Instruments
- Package
- X2SON
- Pins
- 4
- Details
- 300mA, Low-Dropout Regulator With Foldback Current Limit
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Voltage regulator.
TSM2318CXSOT-23MOSFET, 3 pins, Taiwan SemiconductorMOSFETSOT-233 pinsTaiwan Semiconductor
- What it is
- MOSFET
- Maker
- Taiwan Semiconductor
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: MOSFET.
3 more parts have no package on record
SGM808B-5.2XKB5GVoltage supervisor, 5 pins, SG MicroVoltage supervisorNot recorded5 pinsSG Micro
- What it is
- Voltage supervisor
- Maker
- SG Micro
- Package
- Not recorded
- Pins
- 5
- Details
- Small Package, High Precision Voltage Detector
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Integrated circuit.
SGM2045-2.50XXDH4GLDO regulator, 4 pins, SG MicroLDO regulatorNot recorded4 pinsSG Micro
- What it is
- LDO regulator
- Maker
- SG Micro
- Package
- Not recorded
- Pins
- 4
- Details
- 2.50 V output, 300mA, Low VIN, Ultra-Low Noise and High PSRR Linear Regulator
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Voltage regulator.
SS1080HESchottky diode, Galaxy MicroelectronicsSchottky diodeNot recordedNot recordedGalaxy Microelectronics
- What it is
- Schottky diode
- Maker
- Galaxy Microelectronics
- Package
- Not recorded
- Pins
- Not recorded
- Details
- 1A, 80V, Surface Mount Schottky Barrier Rectifiers
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky 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.
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.
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.
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.
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.
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.
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.
MOSFET
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
- 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.
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