SMD code P31
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.
P31 on a chip capacitor
0.31 pF
0.31 pF capacitor
The p is both the decimal point and the unit: 0.31 pF.
Check it with a meter
Lift one end and measure it on a capacitance range. A good one reads close to 0.31 pF. In circuit the meter also sees everything connected across it, so the reading means little until it is out. A failed one usually reads near 0 Ω, or a steady low resistance, on the ohms range, often from a crack. On the board a shorted capacitor shorts its whole rail. A failed reading does not change what to fit: the marking still says 0.31 pF.
On a transistor or diode body (SOT-89-5, SOT-23-5, SOT-89), P31 is a part code instead. Those parts are listed below.
17 parts are printed P31
Not sure which one you have?
Answer up to 4 quick questions and these 17 parts are ranked, with a meter test that settles it. It works on a dead part too.
FB1L2QSOT-233 pins, NEC ElectronicsNot recordedSOT-233 pinsNEC Electronics
- What it is
- Not recorded
- Maker
- NEC Electronics
- Package
- SOT-23
- Pins
- 3
- Details
- Si-npn-Digi: Sw, 30V, 700mA, 200mW, R1/R2=0k47/4k7
- Source
- Published code list
Is it dead? The meter test is below: This part.
HE61CN4301MRSOT-23Voltage supervisor, 3 pins, Heermicr SemicconductorVoltage supervisorSOT-233 pinsHeermicr Semicconductor
- What it is
- Voltage supervisor
- Maker
- Heermicr Semicconductor
- Package
- SOT-23
- Pins
- 3
- Details
- Voltage detector IC: 4.3V±1%, +Reset ODO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
HE7043MNM5R1SOT-23-5Voltage supervisor, 5 pins, Heermicr SemicconductorVoltage supervisorSOT-23-55 pinsHeermicr Semicconductor
- What it is
- Voltage supervisor
- Maker
- Heermicr Semicconductor
- Package
- SOT-23-5
- Pins
- 5
- Details
- Voltage detector IC: 4.3V±1%, +Reset ODO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
HE7043MNNR1SOT-23Voltage supervisor, 3 pins, Heermicr SemicconductorVoltage supervisorSOT-233 pinsHeermicr Semicconductor
- What it is
- Voltage supervisor
- Maker
- Heermicr Semicconductor
- Package
- SOT-23
- Pins
- 3
- Details
- Voltage detector IC: 4.3V±1%, +Reset ODO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
HE7043MNPR1SOT-89Voltage supervisor, 3 pins, Heermicr SemicconductorVoltage supervisorSOT-893 pinsHeermicr Semicconductor
- What it is
- Voltage supervisor
- Maker
- Heermicr Semicconductor
- Package
- SOT-89
- Pins
- 3
- Details
- Voltage detector IC: 4.3V±1%, +Reset ODO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
KIC77A31T2SOT-23Voltage supervisor, 3 pins, KECVoltage supervisorSOT-233 pinsKEC
- What it is
- Voltage supervisor
- Maker
- KEC
- Package
- SOT-23
- Pins
- 3
- Details
- Voltage detector IC: 3.1V±1%, -Reset ODO, Rdt=240ms
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
MIC94031BM4SOT-1434 pins, MicrochipNot recordedSOT-1434 pinsMicrochip
- What it is
- Not recorded
- Maker
- Microchip
- Package
- SOT-143
- Pins
- 4
- Source
- Published code list
Is it dead? The meter test is below: This part.
PDTA143XTSOT-23Digital transistor (PNP, resistors built in), 3 pins, NXPDigital transistor (PNP, resistors built in)SOT-233 pinsNXP
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- NXP
- Package
- SOT-23
- Pins
- 3
- Details
- 50 V, 100 mA PNP resistor-equipped transistor; R1 = 4.7 kΩ, R2 = 10 kΩ
- Source
- Published code list
Is it dead? The meter test is below: Digital transistor.
R1161N311ASOT-23-55 pins, Nisshinbo Micro DevicesNot recordedSOT-23-55 pinsNisshinbo Micro Devices
- What it is
- Not recorded
- Maker
- Nisshinbo Micro Devices
- Package
- SOT-23-5
- Pins
- 5
- Details
- VR-IC: LDO, -CE, 3.1V±2%, 350mA
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
SST271SOT-233 pins, CalNot recordedSOT-233 pinsCal
- What it is
- Not recorded
- Maker
- Cal
- Package
- SOT-23
- Pins
- 3
- Details
- n-FET: AF, LN, 30V, 350mW, Idss=6..50mA, Up<4,5V
- Source
- Published code list
Is it dead? The meter test is below: MOSFET.
TK11231AUSOT-89-55 pins, TokNot recordedSOT-89-55 pinsTok
- What it is
- Not recorded
- Maker
- Tok
- Package
- SOT-89-5
- Pins
- 5
- Details
- VR-IC: LDO, CE, 3,1V±2.4%, 150mA
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
XC6368E312MRSOT-23-5DC-DC converter, 5 pins, TorexDC-DC converterSOT-23-55 pinsTorex
- What it is
- DC-DC converter
- Maker
- Torex
- Package
- SOT-23-5
- Pins
- 5
- Details
- DC/DC voltage converter IC: PWM/PFM st-up, 3.1V±2.5%, 200mA, 180kHz, +CE
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
3 more parts have no package on record
74AUP1T1326GTNXPNot recordedNot recordedNot recordedNXP
- What it is
- Not recorded
- Maker
- NXP
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS logic IC: Dual supply buffer/line drive with 3-state output
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
KIC77A31M2Voltage supervisor, KECVoltage supervisorNot recordedNot recordedKEC
- What it is
- Voltage supervisor
- Maker
- KEC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Voltage detector IC: 3.1V±1%, -Reset ODO, Rdt=240ms
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
TK11231AMTokNot recordedNot recordedNot recordedTok
- What it is
- Not recorded
- Maker
- Tok
- Package
- Not recorded
- Pins
- Not recorded
- Details
- VR-IC: LDO, CE, 3,1V±2.4%, 150mA
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
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.
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.
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.
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.
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.
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.
Printed with a code easy to misread as P31
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 P31
For a marking with its end worn or burnt off. Each code has a page of its own.
Codes not listed here are printed on 59 more parts.
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