Texas Instruments SN74HC125N

Overview

SN74HC125N from Texas Instruments is a quadruple 3-state buffer IC used for digital signal enabling and bus isolation in TTL/CMOS logic systems. It operates across 2 V to 6 V supply, supports –40°C to +85°C ambient, delivers propagation delay ≤31 ns at 6 V, and drives up to 10 LSTTL loads. It is commonly deployed in 4-bit data bus control applications where output enable sequencing is required.

For engineers reviewing the SN74HC125N datasheet, SN74HC125N pinout, SN74HC125N application, or SN74HC125N equivalent, key selection criteria include its 14-pin PDIP package, active-low 3-state enable architecture per channel, guaranteed VOH ≥5.48 V and VOL ≤0.33 V at 6 V/7.8 mA, and compatibility with standard CMOS input thresholds.

Technical Context

This device implements four independent non-inverting buffers (Y = A), each with an active-low 3-state output enable (OE) input. All channels share a common VCC and GND, and operate synchronously under identical supply and temperature conditions.

Each buffer exhibits balanced CMOS drive capability-capable of sourcing and sinking up to ±7.8 mA while maintaining VOH ≥3.98 V and VOL ≤0.33 V at 4.5 V. Input transition time must be ≤400 ns at 6 V to prevent shoot-through current and oscillation due to standard CMOS input structure.

Key Specifications

Pinout & Package

SN74HC125N uses a 14-pin plastic dual in-line package (PDIP) with 19.30 mm × 6.40 mm body size and through-hole mounting. Pin 1 is top-left corner when notch faces upward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT125N and 74LCX125N, the SN74HC125N offers broader supply flexibility (2–6 V) and industrial temperature support, making it the default choice for multi-voltage legacy upgrades and ruggedized control hardware where pin compatibility and thermal reliability outweigh marginal speed gains.

Availability

SN74HC125N is available at Aetrix Electronics and suitable for industrial control panels, test equipment interfaces, and legacy system upgrades requiring stable component supply and long-term obsolescence management.

Supply support for SN74HC125N 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 manufacturer specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74HC125N belongs to TI's industry-standard 74HC logic family, designed specifically for reliable, low-power digital signal routing and bus isolation in mixed-voltage systems.

FAQ

What is the maximum capacitive load the SN74HC125N can drive while meeting datasheet timing specifications?

The SN74HC125N is characterized for CL ≤70 pF in typical design procedures. At 6 V and CL = 50 pF, propagation delay is guaranteed ≤31 ns; exceeding 70 pF increases delay nonlinearly and may violate setup/hold margins. For larger loads, add a series resistor to limit output current per Absolute Maximum Ratings.

Can unused inputs on the SN74HC125N be left floating?

No. Unused inputs on the SN74HC125N must be terminated to VCC or GND using direct connection or a 10-kΩ pull-up/down resistor. Floating CMOS inputs cause undefined logic states, increased ICC, and potential oscillation due to slow edge rates violating the recommended input transition time specification.

Does the SN74HC125N support 3.3 V operation with guaranteed performance?

Yes. The SN74HC125N is fully specified at 3.3 V: VOH ≥2.97 V and VOL ≤0.33 V at IOL = 6 mA, propagation delay ≤20 ns (typ), and VIH/VIL thresholds scaled accordingly. Its 2 V–6 V operating range makes it suitable for direct 3.3 V system integration without level translation.

What is the thermal resistance (RθJA) of the SN74HC125N in its PDIP package?

The SN74HC125N in PDIP (N) package has RθJA = 63.0°C/W, per TI's SCLS104F datasheet revision F. This value assumes JEDEC-standard 2S2P board layout; actual board-level thermal performance depends on copper area, airflow, and adjacent heat sources.

How does the SN74HC125N behave when OE is high and A is driven?

When OE is high (logic 1), the corresponding Y output enters high-impedance (high-Z) state regardless of A's logic level. In this mode, the output draws ≤0.5 µA leakage current (IOZ), and external pull-up/pull-down resistors determine the net voltage at Y - essential for bus arbitration and power-saving isolation.