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WhatSMDSign in

SMD code SIs

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.

The last letter, s, is lower case, which on NXP and Philips parts is a date or factory code, so it was set aside and SI was searched.

2 parts are printed SIs

Not sure which one you have?

Answer up to 4 quick questions and these 2 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • BSS127SOT-23N-channel MOSFET, 3 pins, Infineon
    What it is
    N-channel MOSFET
    Maker
    Infineon
    Package
    SOT-23
    Pins
    3
    Details
    N-Channel Small Signal MOSFET 600 V in SOT23 package
    Source
    From the manufacturer's datasheet

    Is it dead? The meter test is below: N-channel MOSFET.

    Datasheetfor BSS127, opens in a new tab
  • 1 more part has no package on record
    • TLV1701AIDRLComparator, 5 pins, Texas Instruments
      What it is
      Comparator
      Maker
      Texas Instruments
      Package
      Not recorded
      Pins
      5
      Details
      2.2-V to 36-V, microPower Comparator
      Source
      From the manufacturer's datasheet

      Is it dead? The meter test is below: Integrated circuit.

      Datasheetfor TLV1701AIDRL, opens in a new tab

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.

N-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 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.

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.

Printed with a code easy to misread as SIs

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 SIs

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 34 more parts.

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