The SN74LVC1G125-Q1 is a single-gate 3-state bus buffer (a single line driver). Its job is to put a signal onto a shared net only when allowed: when the output-enable (OE) is low, the output Y simply follows the input A; when OE is high, the output is switched to a high-impedance (Hi-Z) state and effectively disconnects from the bus. That single ability — drive or get out of the way — is what lets several sources share one wire without contention.

As a “little-logic” part it places that one buffer exactly where it is needed: to isolate a sensor from a shared SPI line, to drive a longer trace, or to gate a clock onto a backplane. Because the inputs are 5.5 V-tolerant and the output swings to V_CC, the device also performs a clean down-translation — accept a 5 V signal, present it at a 3.3 V or 1.8 V rail — while still offering a strong ±24 mA drive at 3.3 V.

Two robustness features matter in real systems. The “-Q1” automotive qualification (AEC-Q100 Temperature Grade 1, −40 °C to +125 °C) lets it serve vehicle electronics, and the I_off partial-power-down circuit makes it safe for live insertion and back-drive situations. It draws only about 10 µA quiescent.

Note: Values are from the Texas Instruments SN74LVC1G125-Q1 data sheet (SGES002E). Confirm every parameter against the latest data sheet before committing a design.

This order option uses the DCK package — a 5-pin SC-70 (JEDEC MO-203, ~1.1 mm maximum height, body about 2.0 mm × 1.25 mm on a 0.65 mm pitch), with a Pb-free / RoHS (G4) finish. SC-70 is a common compromise for single-gate logic: smaller than SOT-23 yet easier to place and rework than the tiny SON/DRY outline. The same die is also offered in DRY (SON) and DBV (SOT-23).

The dimensioned drawing below gives the SC-70-5 body and lead geometry for the land pattern and assembly stencil.

The buffer maps its enable, input, output and supply pair onto five pins (top view):

• Pin 1 – OE (Output Enable, active-low): low enables the output (Y = A); high forces Hi-Z. 5.5 V-tolerant.
• Pin 2 – A (Input): data input; 5.5 V-tolerant.
• Pin 3 – GND: Ground (0 V) reference.
• Pin 4 – Y (Output): 3-state output; drives ±24 mA at 3.3 V or sits at Hi-Z.
• Pin 5 – V_CC: Supply, 1.65 V to 5.5 V; decouple with a local 0.1 µF capacitor.

The closest functional relatives are other single 3-state buffers. Note the enable polarity: the SN74LVC1G126 is the active-HIGH counterpart of this active-LOW part. Confirm family, package and enable sense before substituting.

Logic Family Comparison

Texas Instruments (TI, NASDAQ: TXN), of Dallas, Texas, is a leading logic supplier and the originator of single-gate “little-logic.” Its LVC family is the wide-supply, 5 V-tolerant workhorse for bus interfacing, and the “-Q1” variants are AEC-Q100 qualified for automotive use.

The governing document is the SN74LVC1G125-Q1 data sheet (SGES002E), which defines the 3-state behaviour, the I_off partial-power-down circuit, the timing and the DCK/DRY/DBV packages. InFortune Electronics supplies the device under code 1P1G125QDCKRG4Q1 and provides sourcing and technical support.