Texas Instruments SN74HC125D

Overview

SN74HC125D from Texas Instruments is a quadruple 3-state buffer IC used for digital signal enablement and bus isolation in logic-level interfacing circuits. It features four independent non-inverting buffers (Y = A), operates from 2 V to 6 V, supports –40°C to +85°C ambient temperature, and delivers propagation delays as low as 11 ns at 6 V with 50 pF load - commonly deployed in 4-bit data bus control and bidirectional I/O expansion.

For engineers reviewing the SN74HC125D datasheet, SN74HC125D pinout, SN74HC125D application, or SN74HC125D equivalent, this page provides verified functional identity, SOIC-14 package mapping, confirmed 3-state output behavior, real-world timing specs (tpd, ten, tdis), and validated alternative options for bus buffering and signal gating use cases.

Technical Context

The SN74HC125D implements four identical CMOS buffer gates, each with an active-low 3-state output enable (OE) controlling high-impedance or driven output states. Its Boolean function Y = A is strictly positive-logic, with no internal inversion or latching.

All inputs are standard CMOS with ≤10 pF input capacitance and ±1 µA leakage at 6 V; outputs provide balanced sourcing/sinking capability up to ±7.8 mA while maintaining VOH ≥ 3.98 V and VOL ≤ 0.33 V under load - enabling reliable fanout to 10 LSTTL loads without external level-shifting.

Key Specifications

Pinout & Package

SN74HC125D is housed in a 14-pin SOIC package (body size 8.70 mm × 3.90 mm) with standard JEDEC MS-012AC footprint and gull-wing leads. Thermal resistance RθJA is 133.6°C/W, suitable for natural-convection PCB layouts without forced cooling.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC125D, SN74HCT125D offers improved compatibility with older TTL sources but shares identical SOIC-14 packaging and 3-state functionality; 74LCX125MTCX delivers superior speed and ESD robustness at 3.3 V but sacrifices 5 V interoperability - making SN74HC125D the optimal general-purpose choice for mixed-voltage industrial control.

Availability

SN74HC125D is available at Aetrix Electronics and suitable for industrial bus isolation, microcontroller I/O expansion, legacy TTL interface adaptation, and test fixture signal gating requiring stable component supply across long-lifecycle embedded programs.

Supply support for SN74HC125D 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 50 years of innovation in high-reliability logic families.

The SN74HC125D belongs to TI's 74HC high-speed CMOS logic series, designed specifically for low-power, wide-supply-range digital interfacing in industrial, automotive, and communications equipment.

FAQ

What is the logic function implemented by the SN74HC125D?

The SN74HC125D implements four independent non-inverting buffer gates, each performing the Boolean function Y = A in positive logic. Each channel has a dedicated active-low output enable (OE) input that places the corresponding Y output into a high-impedance state when asserted LOW. The SN74HC125D does not invert, latch, or decode signals - it simply conditions and gates digital logic levels with 3-state control.

Can the SN74HC125D operate reliably at 3.3 V supply voltage?

Yes, the SN74HC125D is fully specified for operation at 3.3 V: VIH is guaranteed ≥ 2.0 V and VIL ≤ 0.8 V at VCC = 3.3 V, ensuring robust noise margins with standard 3.3 V CMOS outputs. Propagation delay remains ≤ 19 ns (typical) at 3.3 V with 50 pF load, and ICC stays below 20 µA - making SN74HC125D a proven choice for 3.3 V system interfacing without level translation.

What is the maximum capacitive load the SN74HC125D can drive while meeting datasheet timing specs?

The SN74HC125D is characterized for CL = 50 pF and CL = 150 pF loads in its switching characteristics tables. At 6 V supply, tpd is guaranteed ≤ 31 ns for CL = 50 pF and ≤ 39 ns for CL = 150 pF. While larger loads may be driven, TI recommends limiting total output capacitance to ≤ 70 pF for optimal timing margin and signal integrity - exceeding this may increase propagation delay and transition time beyond published limits in the SN74HC125D datasheet.

How should unused inputs and outputs be handled on the SN74HC125D?

Unused inputs on the SN74HC125D must be terminated to a valid logic level - either VCC or GND - to prevent floating states that cause excessive current draw or oscillation. Unused outputs may be left unconnected (floating) since they present high impedance in the disabled state. TI explicitly advises against tying outputs directly to VCC or GND. For unused OE inputs, tie to VCC to keep associated buffers enabled, or to GND to force high-impedance - depending on system default requirement.

Is the SN74HC125D pin-compatible with other packages in the same logic family?

Yes, the SN74HC125D (SOIC-14) shares identical pin configuration and function mapping with other 14-pin variants including SN74HC125DB (SSOP-14), SN74HC125N (PDIP-14), and SN74HC125PW (TSSOP-14). All share the same pin numbering, signal assignments (1OE, 1A, 1Y, ..., VCC, GND), and electrical behavior - enabling direct PCB footprint substitution where package height and thermal constraints allow. The SN74HC125D pinout is fully documented in TI's SCLS104F datasheet Figure 5-1.