Texas Instruments SN74HC126DBR

Overview

SN74HC126DBR 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 ≤31 ns propagation delay at 6 V, and drives up to 10 LSTTL loads. It is commonly deployed in bidirectional data bus control and level-shifting applications where output disable capability is required.

For engineers reviewing the SN74HC126DBR datasheet, SN74HC126DBR pinout, SN74HC126DBR application, or SN74HC126DBR equivalent, key selection considerations include its 14-pin SSOP package, independent per-channel 3-state control (OE), CMOS-compatible input thresholds, balanced output drive (±7.8 mA), and thermal resistance of 108.0°C/W (R_θJA).

Technical Context

This device implements four electrically isolated buffer gates, each performing Y = A in positive logic with individual 3-state output enable (OE) control. All inputs are standard CMOS with high impedance and ≤10 pF input capacitance; outputs feature balanced sourcing/sinking capability and clamp diodes for ESD protection.

Each channel operates independently: when OE is low, the output enters high-impedance state (Z); when OE is high, the output replicates the input (Y = A). The SSOP-14 package (6.50 mm × 5.30 mm) supports surface-mount assembly and provides defined thermal performance (R_θJA = 108.0°C/W) under JEDEC-standard board conditions.

Key Specifications

Pinout & Package

SN74HC126DBR uses a 14-pin Shrink Small Outline Package (SSOP) with 0.65 mm lead pitch and body dimensions of 6.50 mm × 5.30 mm. Pin 1 is marked by a beveled corner or dot; pins are numbered counter-clockwise from top-left when viewed from the top with marking side up.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT126DBR and 74LVC126ADBR, SN74HC126DBR uniquely balances wide supply tolerance (2–6 V), industrial temperature rating (–40°C to +85°C), and predictable 3-state timing-making it the preferred choice for general-purpose bus isolation where voltage flexibility and reliability outweigh raw speed.

Availability

SN74HC126DBR is available at Aetrix Electronics and suitable for industrial automation, test equipment, and embedded control applications requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for SN74HC126DBR 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 SN74HC126DBR belongs to TI's 74HC high-speed CMOS logic family, designed specifically for low-power, pin-compatible replacements of legacy TTL devices in noise-sensitive and thermally constrained applications.

FAQ

What is the maximum capacitive load SN74HC126DBR can reliably drive?

SN74HC126DBR is characterized for optimal performance with ≤70 pF total load capacitance, including trace and receiver input capacitance. At 6 V supply and CL = 50 pF, propagation delay remains ≤31 ns and output transition time ≤15 ns. Driving >100 pF may increase delay unpredictably and risk exceeding absolute max output current (±35 mA); a series resistor is recommended for larger loads to limit peak current per Absolute Maximum Ratings.

Can SN74HC126DBR operate at 2.5 V supply voltage?

Yes, SN74HC126DBR is fully specified from 2 V to 6 V. At 2.5 V, VIH is guaranteed ≥1.7 V and VIL ≤0.8 V per Recommended Operating Conditions; VOH ≥2.3 V and VOL ≤0.25 V at IOL = 6 mA. Propagation delay increases to 180 ns (max) at CL = 50 pF, making it suitable for sub-5 MHz control logic but not high-speed data paths.

How should unused inputs and outputs be handled on SN74HC126DBR?

Unused inputs on SN74HC126DBR must be terminated to V_CC or GND-never left floating-to prevent oscillation, excess current draw, or undefined logic states. Unused outputs may be left unconnected (floating) since the 3-state architecture inherently isolates them when OE is LOW. TI recommends 10-kΩ pull-up/down resistors for unused inputs requiring configurable default states.

Does SN74HC126DBR support hot-swap or live-insertion?

No, SN74HC126DBR does not support hot-swap. Its Absolute Maximum Ratings specify no voltage on any pin before V_CC is applied, and the input clamp diodes require V_CC to be present to safely shunt transients. Applying signals to inputs or outputs prior to power-up risks exceeding IIK/IOK limits (±20 mA) and causing permanent damage. Power sequencing must ensure V_CC is stable before any I/O signals are asserted.

What is the thermal resistance (R_θJA) of SN74HC126DBR in its SSOP package?

The junction-to-ambient thermal resistance R_θJA for SN74HC126DBR in the 14-pin SSOP (DB) package is 108.0°C/W under JEDEC-standard 2S2P board conditions. This value assumes a 1-inch² copper pad with two vias; actual board layout significantly impacts real-world thermal performance. For continuous 7.8 mA output current at 6 V, power dissipation remains below 1 mW per channel, making thermal derating unnecessary in typical applications.