Texas Instruments SN74HCT125DE4

Overview

SN74HCT125DE4 from Texas Instruments is a quadruple 3-state bus buffer gate IC with TTL-compatible inputs and independent enable control per channel, operating at 4.5–5.5 V, delivering ±6-mA output drive, 12-ns typical propagation delay, and 80-µA max supply current. It serves as a bidirectional data isolator in microcontroller peripheral buses and memory address latching circuits.

For engineers reviewing the SN74HCT125DE4 datasheet, SN74HCT125DE4 pinout, SN74HCT125DE4 application, or SN74HCT125DE4 equivalent, key selection criteria include 3-state output timing (ten/tdis ≤35 ns), input voltage compatibility (VIH = 2 V, VIL = 0.8 V), thermal resistance (RθJA = 138.7 °C/W), and SOIC-14 package footprint compliance.

Technical Context

This device implements four independent non-inverting buffers (Y = A) with individual 3-state output-enable (OE) inputs. Each channel transitions to high-impedance when its OE is logic high, enabling time-multiplexed bus sharing without contention.

It uses HCMOS technology with TTL-level input thresholds, ensuring direct interfacing with legacy 5-V logic families. The design supports CL = 50 pF load conditions and specifies switching characteristics across –40°C to +85°C ambient operation.

Key Specifications

Pinout & Package

SN74HCT125DE4 is housed in a 14-pin SOIC (D) package with nominal body size 8.65 mm × 3.90 mm and maximum height 1.75 mm, compliant with JEDEC MS-012AB and IPC-7351 land pattern standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT125DE4, SN74HCT125N offers easier hand-soldering but larger board area and higher thermal resistance, while 74HCT125PW reduces footprint by 40% but demands finer-pitch assembly and tighter thermal management.

Availability

SN74HCT125DE4 is available at Aetrix Electronics and suitable for industrial control systems, embedded instrumentation, and digital test equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant SOIC packaging.

Supply support for SN74HCT125DE4 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 U.S.-based semiconductor company specializing in analog, embedded processing, and logic solutions, with over 90 years of innovation in industrial and automotive electronics.

SN74HCT125DE4 belongs to the 74HCT logic family designed for TTL-to-CMOS interfacing in industrial-grade 5-V systems, emphasizing robust noise immunity, predictable timing, and wide temperature operation.

FAQ

What is the maximum clock frequency supported by SN74HCT125DE4 in a bus-driving application?

The SN74HCT125DE4 does not operate as a clocked device but as a combinatorial buffer. Its 10–22 ns propagation delay (at CL = 50 pF) supports reliable data transfer in synchronous buses up to approximately 25 MHz, assuming setup/hold timing margins are met by the driving and receiving logic. System-level frequency depends on total path delay, not the IC's internal clock.

Can SN74HCT125DE4 be used with 3.3-V microcontrollers?

No - SN74HCT125DE4 requires a 4.5–5.5-V supply and has TTL-compatible input thresholds (VIH = 2.0 V min). Direct connection to 3.3-V logic violates VIH specification and risks unreliable high-level detection. A level translator or 3.3-V–compatible buffer such as SN74LVC125A is required for mixed-voltage interfacing.

Does SN74HCT125DE4 require external pull-up resistors on OE pins?

Yes - to ensure defined high-impedance state during power-up/power-down, each OE pin should be tied to VCC via a pull-up resistor. TI recommends minimum resistance based on driver sink capability; a 10-kΩ resistor is commonly used and ensures fast, reliable disable before supply stabilization.

What is the thermal performance difference between SN74HCT125DE4 and SN74HCT125N?

SN74HCT125DE4 (SOIC-14) has RθJA = 138.7 °C/W, while SN74HCT125N (PDIP-14) has RθJA = 75.3 °C/W. Under identical 6-mA output load and ambient conditions, the PDIP version runs ~40% cooler. This makes SN74HCT125N preferable in thermally constrained through-hole applications, whereas SN74HCT125DE4 suits compact surface-mount layouts with adequate airflow or copper pour.

Is SN74HCT125DE4 pin-compatible with older 74LS125 variants?

Yes - SN74HCT125DE4 maintains identical pinout, function table, and DC logic levels as 74LS125, enabling drop-in replacement in existing 5-V designs. However, it draws significantly less quiescent current (80 µA vs. ~15 mA) and offers faster switching (12 ns vs. ~25 ns), improving both power efficiency and timing margin.