SMD marking

54in SOT-323

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.

6 parts are printed 54

Not sure which one you have?

Answer up to 4 quick questions and these 6 parts are ranked, with a meter test that settles it. It works on a dead part too.

DTA114YU3SOT-323Digital transistor (PNP, resistors built in), 3 pins, ROHMDigital transistor (PNP, resistors built in)3 pinsROHM
What it is
Digital transistor (PNP, resistors built in)
Maker
ROHM
Package
SOT-323
Pins
3
Details
PNP digital transistor (bias resistor built-in); R1 = 10kOhm, R2 = 47kOhm
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor DTA114YU3, opens in a new tab
DTA114YUASOT-323Digital transistor (PNP, resistors built in), 3 pins, JSCJDigital transistor (PNP, resistors built in)3 pinsJSCJ
What it is
Digital transistor (PNP, resistors built in)
Maker
JSCJ
Package
SOT-323
Pins
3
Details
Digital transistor (bias resistors built in), PNP
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor DTA114YUA, opens in a new tab
DTA114YUBSOT-323Digital transistor (PNP, resistors built in), 3 pins, ROHMDigital transistor (PNP, resistors built in)3 pinsROHM
What it is
Digital transistor (PNP, resistors built in)
Maker
ROHM
Package
SOT-323
Pins
3
Details
PNP digital transistor (bias resistor built-in); R1 = 10kOhm, R2 = 47kOhm
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor DTA114YUB, opens in a new tab
PDTC143ZUSOT-323Digital transistor (NPN, resistors built in), 3 pins, NexperiaDigital transistor (NPN, resistors built in)3 pinsNexperia
What it is
Digital transistor (NPN, resistors built in)
Maker
Nexperia
Package
SOT-323
Pins
3
Details
50 V, 100 mA NPN resistor-equipped transistor; R1 = 4.7 kΩ, R2 = 47 kΩ
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor PDTC143ZU, opens in a new tab
2 more parts have no package on record. Nothing rules them out, so they stay.
- BAT17-04Schottky diode, InfineonSchottky diodeNot recordedInfineon
  What it is
  Schottky diode
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor BAT17-04, opens in a new tab
- DTA114YEDigital transistor (PNP, resistors built in), JSCJDigital transistor (PNP, resistors built in)Not recordedJSCJ
  What it is
  Digital transistor (PNP, resistors built in)
  Maker
  JSCJ
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Digital transistor (bias resistors built in), PNP
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor DTA114YE, opens in a new tab

2 more parts are printed with a code easy to misread as 54

Printed with a code easy to misread

One character differs, and it is one that is easy to confuse under a lamp. The odd one out is marked on each.

SD103AXM5printed S4Schottky diode, Taiwan SemiconductorSchottky diodeNot recordedTaiwan Semiconductor
Printed S4 on the part. Easy to misread as 54. Check that character with a loupe before you order anything.
What it is
Schottky diode
Maker
Taiwan Semiconductor
Package
Not recorded
Pins
Not recorded
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor SD103AXM5, opens in a new tab
SN74LVC1G17DPWprinted S4Logic gate, 5 pins, Texas InstrumentsLogic gate5 pinsTexas Instruments
Printed S4 on the part. Easy to misread as 54. Check that character with a loupe before you order anything.
What it is
Logic gate
Maker
Texas Instruments
Package
Not recorded
Pins
5
Details
Single Schmitt-Trigger Buffer
Source
From the manufacturer's datasheet
Is it dead?
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.
Datasheetfor SN74LVC1G17DPW, opens in a new tab

7 more parts have codes that begin with 54

Codes that begin with 54

For a marking with its end worn or burnt off. Each one shows its full printed code.

BAS40AW-AUprinted S42SOT-323Schottky diode, 3 pins, PanjitSchottky diode3 pinsPanjit
Printed S42. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Schottky diode
Maker
Panjit
Package
SOT-323
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BAS40AW-AU, opens in a new tab
BAS40CW-AUprinted S43SOT-323Schottky diode, 3 pins, PanjitSchottky diode3 pinsPanjit
Printed S43. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Schottky diode
Maker
Panjit
Package
SOT-323
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BAS40CW-AU, opens in a new tab
BAS40SW-AUprinted S44SOT-323Schottky diode, 3 pins, PanjitSchottky diode3 pinsPanjit
Printed S44. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Schottky diode
Maker
Panjit
Package
SOT-323
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BAS40SW-AU, opens in a new tab
BAS40W-AUprinted S40SOT-323Schottky diode, 3 pins, PanjitSchottky diode3 pinsPanjit
Printed S40. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Schottky diode
Maker
Panjit
Package
SOT-323
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BAS40W-AU, opens in a new tab
3 more parts have no package on record. Nothing rules them out, so they stay.
- PJQ4542S6P-AUprinted 542WMOSFET, PanjitMOSFETNot recordedPanjit
  Printed 542W. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  MOSFET
  Maker
  Panjit
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor PJQ4542S6P-AU, opens in a new tab
- PJQ4548S6VP-AUprinted 548XMOSFET, PanjitMOSFETNot recordedPanjit
  Printed 548X. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  MOSFET
  Maker
  Panjit
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor PJQ4548S6VP-AU, opens in a new tab
- SS54ALHprinted 54ALHSchottky diode, Taiwan SemiconductorSchottky diodeNot recordedTaiwan Semiconductor
  Printed 54ALH. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  Schottky diode
  Maker
  Taiwan Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Rectifier schottky
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor SS54ALH, opens in a new tab

Open this in the search to correct a character or try another package.

6 parts are printed 54

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Printed with a code easy to misread

Is it dead?

Is it dead?

Codes that begin with 54

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?