SMD code N21 in 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 and published code lists.
2 parts in SOT-323 are printed N21
Not sure which one you have?
Answer up to 4 quick questions and these 4 parts are ranked, with a meter test that settles it. It works on a dead part too.
DDTC144VUASOT-323Digital transistor (NPN, resistors built in), Diodes IncorporatedDigital transistor (NPN, resistors built in)Diodes Incorporated
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- Diodes Incorporated
- Package
- SOT-323
- Pins
- 3
- Details
- dtr npn 50V 0.1A 47k/10k 0.2W
- Source
- Published code list
Is it dead? The meter test is below: Digital transistor.
LDTC114TWT1GSOT-323Digital transistor (NPN, resistors built in), LRCDigital transistor (NPN, resistors built in)LRC
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- LRC
- Package
- SOT-323
- Pins
- 3
- Details
- NPN transistor: Sw., 50V, 100mA, B=100..600, R1=10k
- Source
- Published code list
Is it dead? The meter test is below: Digital transistor.
2 more parts have no package on record. Nothing rules them out, so they stay.
NX30P0121UKLoad switch, NXPLoad switchNXP
- What it is
- Load switch
- Maker
- NXP
- Package
- Not recorded
- Pins
- Not recorded
- Details
- 1 General description 2 Features and benefits 3 Applications
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Load switch.
LDTC114TET1GDigital transistor (NPN, resistors built in), LRCDigital transistor (NPN, resistors built in)LRC
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- LRC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Digital transistor (bias resistors built in), NPN, IC 100 mA, VCEO 50 V
- Source
- An older or alternative marking, from a 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.
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.
Load switch
Voltage, board powered, black probe on ground.
Working, it reads
Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.
Dead, it reads
- Output at the input voltage while switched off: the pass element has shorted.
- Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
- On the board:
- An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
- 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 pinout and whether the enable is active high or low differ between parts. The datasheet gives both.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed with a code easy to misread as N21
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
Codes that begin with N21
For a marking with its end worn or burnt off. Each code has a page of its own.
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