Texas Instruments SN74HC125DT

Overview

SN74HC125DT from Texas Instruments is a quadruple non-inverting buffer with 3-state outputs, designed for bus interface and signal enable functions in digital logic systems. It operates across 2 V to 6 V supply, supports –40°C to +85°C ambient, delivers ≤31 ns propagation delay at 6 V, and drives up to 10 LSTTL loads - enabling clean signal routing in mixed-voltage microcontroller I/O expansion applications.

For engineers reviewing the SN74HC125DT datasheet, SN74HC125DT pinout, SN74HC125DT application, or SN74HC125DT equivalent, this page provides verified functional identity, SOIC-14 package mapping, confirmed 3-state timing parameters (tpd, ten, tdis), real-world bus isolation use cases, and two validated alternative parts with documented functional and application differences.

Technical Context

This device implements four independent CMOS buffer gates, each performing Y = A in positive logic with active-low 3-state output control (OE). All inputs are standard high-impedance CMOS with input capacitance ≤10 pF and leakage ≤±1 µA at 6 V.

Each channel features balanced drive capability (IOH/IOZ ≤–7.8 mA / ±5 µA), defined switching characteristics under CL = 50 pF and 150 pF loads, and thermal metrics including RθJA = 133.6°C/W for the SOIC-14 package - confirming suitability for moderate-density PCB layouts without forced airflow.

Key Specifications

Pinout & Package

SN74HC125DT is supplied in a 14-pin SOIC (D) package measuring 8.70 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads compatible with automated SMT assembly and IPC-7351B footprints.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buffer-with-3-state-output applications.

Compared with SN74HC125DT, SN74HCT125DR offers TTL-input compatibility at the cost of reduced noise margin in CMOS-only systems, while 74LVC125APW,118 delivers superior speed and density but requires careful attention to 1.65 V minimum supply and tighter layout controls.

Availability

SN74HC125DT is available at Aetrix Electronics and suitable for industrial control panels, test equipment signal routing, and microcontroller peripheral expansion requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74HC125DT includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader delivering analog and embedded processing solutions, with over 90 years of innovation in logic, power management, and signal chain technologies.

The SN74HC125DT belongs to TI's industry-standard 74HC logic family, engineered for reliable, low-power digital interfacing in industrial, automotive, and communications infrastructure applications where predictable timing and wide voltage operation are essential.

FAQ

What is the function of the OE pins on the SN74HC125DT?

The SN74HC125DT features four active-low output enable (OE) pins - 1OE through 4OE - each controlling the 3-state output of its corresponding buffer channel. When an OE pin is driven LOW, the associated Y output follows the A input (Y = A); when HIGH, the Y output enters high-impedance (Hi-Z) state. This allows independent bus arbitration per channel, critical for multi-master digital systems. Each OE pin must be actively driven or pulled to a defined logic level - floating OEs cause unpredictable output behavior.

Can the SN74HC125DT operate reliably at 3.3 V supply?

Yes, the SN74HC125DT is fully specified for 3.3 V operation: VOH ≥ 3.84 V and VOL ≤ 0.33 V at IOL = 6 mA, VIH = 3.15 V, and VIL = 1.35 V - meeting standard 3.3 V CMOS interface requirements. Propagation delay is 14 ns (typ) at 3.3 V with CL = 50 pF, and ICC remains ≤80 µA. Its 2–6 V range makes it ideal for mixed-voltage boards where 3.3 V logic interfaces with 5 V peripherals via buffered signals.

What is the maximum capacitive load the SN74HC125DT can drive while maintaining timing specs?

The SN74HC125DT is characterized for CL = 50 pF and CL = 150 pF loads in its switching specifications, with tpd, ten, and tdis guaranteed across both conditions. While it can physically drive larger capacitances, TI recommends limiting total output load to ≤70 pF to ensure full compliance with published timing margins and avoid excessive transition times or ringing. For heavier loads, add a series resistor (e.g., 22–47 Ω) near the output to limit peak current and maintain signal integrity.

How should unused inputs and outputs be handled on the SN74HC125DT?

Unused inputs on the SN74HC125DT must be terminated to a valid logic level - either VCC or GND - using direct connection or a pull-up/pull-down resistor (10 kΩ typical) to prevent floating, oscillation, and excess current draw. Unused outputs may be left floating when their OE is HIGH (Hi-Z state), but must never be tied directly to VCC or GND, as this violates absolute maximum ratings and risks damage during 3-state transitions.

Does the SN74HC125DT support hot-swap or live-insertion applications?

The SN74HC125DT is not rated for hot-swap operation. Its absolute maximum ratings specify no voltage on any pin before VCC is applied, and the internal clamp diode structure (IIK/IOK ±20 mA) does not provide robust protection against insertion transients. For live-insertion scenarios, external protection circuitry - such as series current-limiting resistors and TVS diodes - is required. TI recommends verifying system-level stress limits per JEDEC JESD78 and conducting board-level ESD testing before deployment.