Texas Instruments SN74HC125DBR

Overview

SN74HC125DBR from Texas Instruments is a quadruple 3-state buffer IC used for digital signal enablement and bus isolation in logic-level interfacing circuits. It operates across 2 V to 6 V supply, supports –40°C to +85°C ambient, delivers propagation delay as low as 11 ns at 6 V, and features balanced CMOS outputs capable of sourcing/sinking ±7.8 mA. It is commonly deployed in bidirectional data bus control applications.

For engineers reviewing the SN74HC125DBR datasheet, SN74HC125DBR pinout, SN74HC125DBR application, or SN74HC125DBR equivalent, key selection criteria include its 14-pin SSOP package, active-low 3-state enable architecture per channel, guaranteed VOH/VOL performance across voltage/temperature, and compatibility with LSTTL fanout requirements while reducing power versus legacy TTL.

Technical Context

The SN74HC125DBR implements four independent non-inverting buffers (Y = A) with individual active-low 3-state output enables (OE). Each channel operates with standard CMOS inputs and balanced CMOS 3-state outputs, enabling high-impedance disconnection without leakage-induced floating states.

Its functional modes are defined by OE logic: when OE is low, Y replicates A; when OE is high, Y enters high-impedance state with IOZ ≤ ±0.5 µA at 6 V. Input transition time must be ≤ 400 ns at 6 V to prevent shoot-through current and oscillation.

Key Specifications

Pinout & Package

SN74HC125DBR uses a 14-pin SSOP (Shrink Small Outline Package) with nominal body size 6.50 mm × 5.30 mm and 0.65 mm lead pitch. The package is RoHS-compliant, moisture-sensitive level 1, and rated for reflow up to 260°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT125DBR, the SN74HC125DBR offers wider supply flexibility (2–6 V) but requires external level translation for robust TTL interfacing; compared with 74LVC125ADBR, it sacrifices speed and 3.3 V optimization for universal voltage support and industrial temperature compliance.

Availability

SN74HC125DBR is available at Aetrix Electronics and suitable for industrial control panels, test instrumentation, and embedded data acquisition systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74HC125DBR 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 for industrial, automotive, and communications markets.

The SN74HC125DBR belongs to TI's HC (High-Speed CMOS) logic family, designed for low-power, pin-compatible upgrades to legacy TTL logic in general-purpose digital interfacing and bus management applications.

FAQ

What is the maximum capacitive load the SN74HC125DBR can reliably drive?

The SN74HC125DBR is characterized for optimal performance with capacitive loads ≤70 pF, as verified in TI's application guidance. At 6 V supply and CL = 50 pF, propagation delay remains ≤31 ns and output transition time ≤15 ns. Driving larger loads increases delay and may cause ringing; a series resistor is recommended if CL exceeds 70 pF to limit peak output current within ±7.8 mA limits.

Can unused inputs on the SN74HC125DBR be left floating?

No, unused inputs on the SN74HC125DBR must not be left floating. Standard CMOS inputs have high impedance and undefined voltage states when unconnected, risking oscillation, excessive current draw, or latch-up. TI specifies that all unused inputs be terminated to VCC or GND-typically via 10-kΩ pull-up/down resistors-to maintain stable logic levels and ensure predictable device behavior.

Does the SN74HC125DBR support 3.3 V operation with guaranteed timing?

Yes, the SN74HC125DBR fully supports 3.3 V operation with guaranteed timing. At VCC = 3.3 V and TA = 25°C, typical propagation delay is 17 ns (CL = 50 pF), and worst-case is 45 ns across –40°C to +85°C. All electrical characteristics-including VOH ≥ 3.15 V and VOL ≤ 0.33 V at IOL = 6 mA-are specified and tested at 3.3 V, making SN74HC125DBR suitable for mixed-voltage 3.3 V/5 V system designs.

What is the thermal resistance (RθJA) of the SN74HC125DBR in its SSOP package?

The SN74HC125DBR in the 14-pin SSOP (DB) package has a junction-to-ambient thermal resistance (RθJA) of 108.0°C/W, as measured under JEDEC JESD51-2 conditions. This value assumes a standard 2-layer PCB with 1 in² copper area. For high-density layouts or elevated ambient temperatures, derating of maximum power dissipation (ICC × VCC) is required to maintain TJ < 150°C per absolute maximum ratings.

How does the 3-state enable logic work on the SN74HC125DBR?

The SN74HC125DBR uses active-low 3-state enable inputs (1OE, 2OE, 3OE, 4OE): when an OE pin is driven LOW, the corresponding output (1Y–4Y) actively buffers its input (1A–4A); when OE is HIGH, that output enters high-impedance state with leakage ≤ ±0.5 µA. This allows independent or grouped control of signal paths-e.g., tying all OEs together enables simultaneous bus release, while separate OE control permits selective channel activation.