SMD code A1p
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, p, is lower case, which on NXP and Philips parts is a date or factory code, so it was set aside and A1 was searched.
208 parts are printed A1p
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.
LD39020ADTPU08RDFNLDO 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.
LM3139SOT-23P-channel MOSFET, 3 pins, LeiditechP-channel MOSFETSOT-233 pinsLeiditech
- What it is
- P-channel MOSFET
- Maker
- Leiditech
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: P-channel MOSFET.
LSI1013N3T5GSOT-883P-channel MOSFET, 3 pins, LRCP-channel MOSFETSOT-8833 pinsLRC
- What it is
- P-channel MOSFET
- Maker
- LRC
- Package
- SOT-883
- Pins
- 3
- Details
- MOSFET, P-Channel(with ESD), VDSS 20 V, VGS 6 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: P-channel MOSFET.
MMBD4148CASOT-23Switching diode, 3 pins, Taiwan SemiconductorSwitching diodeSOT-233 pinsTaiwan Semiconductor
- What it is
- Switching diode
- Maker
- Taiwan Semiconductor
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
MMBD4148T-6LSOT-23-6Switching diode, 6 pins, Galaxy MicroelectronicsSwitching diodeSOT-23-66 pinsGalaxy Microelectronics
- What it is
- Switching diode
- Maker
- Galaxy Microelectronics
- Package
- SOT-23-6
- Pins
- 6
- Details
- 0.08A, 85V, Surface Mount Small Signal Switching Diodes
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
MMSZ10SOD-123Zener diode, 2 pins, onsemiZener diodeSOD-1232 pinsonsemi
- What it is
- Zener diode
- Maker
- onsemi
- Package
- SOD-123
- Pins
- 2
- Details
- Zener Voltage Regulators MMSZxxxT1G Series, SZMMSZxxxT1G Series
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
PTVS3V3S1UR-MSSOD-123FTVS diode, 2 pins, MSKSEMITVS diodeSOD-123F2 pinsMSKSEMI
- What it is
- TVS diode
- Maker
- MSKSEMI
- Package
- SOD-123F
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
PZ2FD2V4HASOD-882Zener diode, 2 pins, PrisemiZener diodeSOD-8822 pinsPrisemi
- What it is
- Zener diode
- Maker
- Prisemi
- Package
- SOD-882
- Pins
- 2
- Details
- Zener diode, 2.35 V, 1 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
RBR5LAM40ASOD-128Schottky diode, 2 pins, ROHMSchottky diodeSOD-1282 pinsROHM
- What it is
- Schottky diode
- Maker
- ROHM
- Package
- SOD-128
- Pins
- 2
- Details
- Schottky Barrier Diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
RBR5LAM40ATFSOD-128Schottky diode, 2 pins, ROHMSchottky diodeSOD-1282 pinsROHM
- What it is
- Schottky diode
- Maker
- ROHM
- Package
- SOD-128
- Pins
- 2
- Details
- Schottky Barrier Diode (AEC-Q101 qualified)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
5 more parts have no package on record
LP3401LT1GP-channel MOSFET, LRCP-channel MOSFETNot recordedNot recordedLRC
- What it is
- P-channel MOSFET
- Maker
- LRC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- MOSFET, P-Channel, VDSS 30 V, VGS 12 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: P-channel MOSFET.
LSI1012X6T3BGDual N-channel MOSFET, LRCDual N-channel MOSFETNot recordedNot recordedLRC
- What it is
- Dual N-channel MOSFET
- Maker
- LRC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- MOSFET, Dual-N-Channel(with ESD), VDSS 20 V, VGS 8 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: N-channel MOSFET pair.
PESD3V3L5UFUMWNot recordedNot recordedNot recordedUMW
- What it is
- Not recorded
- Maker
- UMW
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: This part.
RBR5L40ASchottky diode, ROHMSchottky diodeNot recordedNot recordedROHM
- What it is
- Schottky diode
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Schottky Barrier Diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
RBR5L40ADDSchottky diode, ROHMSchottky diodeNot recordedNot recordedROHM
- What it is
- Schottky diode
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Schottky Barrier Diode (AEC-Q101 qualified)
- 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.
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.
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.
N-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 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.
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.
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.
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.
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.
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.
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