Texas Instruments SN74HCT125NE4

Overview

SN74HCT125NE4 from Texas Instruments is a quadruple 3-state bus buffer gate IC with TTL-compatible inputs and independent enable control per channel. It operates at 4.5–5.5 V, delivers ±6-mA output drive, exhibits 12-ns typical propagation delay, and supports high-current bus driving up to 15 LSTTL loads in industrial temperature range (–40°C to +85°C). It is used for bidirectional data bus isolation and memory address buffering in microcontroller peripheral interfaces.

For engineers reviewing the SN74HCT125NE4 datasheet, SN74HCT125NE4 pinout, SN74HCT125NE4 application, or SN74HCT125NE4 equivalent, key selection criteria include 3-state output timing (ten/tdis), input voltage compatibility with legacy TTL logic, low ICC (≤80 µA), thermal resistance (RθJA = 75.3°C/W), and PDIP-14 package suitability for through-hole prototyping and legacy board repair.

Technical Context

This device implements four independent non-inverting buffers (Y = A) with individual active-low 3-state enable inputs (1OE–4OE). Each output enters high-impedance state when its corresponding OE is high, enabling time-division multiplexing of shared buses without contention.

It uses HCMOS technology with TTL-level input thresholds (VIH = 2.0 V min, VIL = 0.8 V max at VCC = 4.5–5.5 V), ensuring interoperability with 5-V TTL systems while maintaining CMOS power efficiency. Output drive strength (±6 mA at 5 V) and fast switching (tpd ≤ 25 ns at CL = 50 pF) support reliable signal integrity on loaded PCB traces.

Key Specifications

Pinout & Package

SN74HCT125NE4 is housed in a 14-pin plastic dual in-line package (PDIP-N), with nominal body size 19.31 mm × 6.35 mm and through-hole mounting. Pin 1 is marked by a notch or dot; the package is RoHS-compliant with NIPDAU lead finish and no MSL rating (through-hole reflow not applicable).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bus buffer applications.

Compared with SN74HCT125N and MC74HCT125NG, the SN74HCT125NE4 offers the tightest ICC specification (≤80 µA), fastest typical propagation delay (12 ns), and guaranteed RoHS compliance with NIPDAU finish - making it optimal for new industrial designs requiring long-term supply assurance and lowest static power.

Availability

SN74HCT125NE4 is available at Aetrix Electronics and suitable for industrial control systems, legacy equipment repair, and microcontroller peripheral expansion requiring stable component supply and through-hole manufacturability.

Supply support for SN74HCT125NE4 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 specializing in analog, embedded processing, and logic solutions with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74HCT125NE4 belongs to TI's 74HCT logic family - designed specifically to provide TTL-compatible input thresholds with CMOS power efficiency for seamless integration into mixed-technology 5-V systems.

FAQ

What is the maximum capacitive load SN74HCT125NE4 can drive while maintaining specified timing?

The SN74HCT125NE4 is characterized for CL = 50 pF and CL = 150 pF loads. At CL = 50 pF, tpd is 10–25 ns; at CL = 150 pF, tpd increases to 16–48 ns. For reliable operation beyond 150 pF, external series termination or reduced edge rates are recommended. The SN74HCT125NE4 output structure supports ≤50 pF for sub-25 ns timing-critical paths.

Can SN74HCT125NE4 be used with a 3.3-V microcontroller I/O?

No - SN74HCT125NE4 requires VCC = 4.5–5.5 V and has TTL-compatible inputs (VIH ≥ 2.0 V), but its outputs swing rail-to-rail at 5 V and are not 3.3-V tolerant. Direct connection to 3.3-V MCU I/O risks damage or logic misreads. Use a level translator (e.g., TXB0104) or select a 3.3-V logic family like SN74LVC125A instead of SN74HCT125NE4.

Is SN74HCT125NE4 pin-compatible with older 74LS125 devices?

Yes - SN74HCT125NE4 uses the same PDIP-14 package and identical pinout as 74LS125, including 1A/1Y/1OE mapping. Its TTL-compatible inputs (VIH = 2.0 V, VIL = 0.8 V) match LS thresholds, and output drive (±6 mA) exceeds LS125's ±8 mA, making SN74HCT125NE4 a functionally superior drop-in replacement in most 5-V systems.

What is the recommended bypass capacitor for SN74HCT125NE4?

Texas Instruments specifies a 0.1-µF ceramic capacitor placed as close as possible to the VCC pin (Pin 14) and GND pin (Pin 7) of SN74HCT125NE4. For systems with high-frequency noise, paralleling with a 1-µF capacitor is acceptable. This ensures stable VCC during output switching transients and prevents ground bounce that could affect timing margins of the SN74HCT125NE4.

Does SN74HCT125NE4 require pull-up resistors on its OE pins?

Not strictly required during normal operation, but TI recommends tying unused OE inputs to VCC via a pull-up resistor (e.g., 10 kΩ) to guarantee high-impedance state at power-up/power-down. This prevents bus contention if OE floats high during reset sequences. For actively controlled OE signals, direct GPIO connection suffices - the SN74HCT125NE4 OE inputs have low leakage (<1 µA), so no external pull-up is needed when driven.