Texas Instruments SN74HC126DT

Overview

SN74HC126DT 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 requiring output disable capability.

For engineers reviewing the SN74HC126DT datasheet, SN74HC126DT pinout, SN74HC126DT application, or SN74HC126DT equivalent, key selection considerations include its 14-pin SOIC (D) package, 3-state output behavior per channel, CMOS input compatibility, and thermal performance metrics such as RθJA = 133.6°C/W - critical for power-sensitive PCB layouts and industrial control designs.

Technical Context

This device implements four independent non-inverting buffers, each with an active-low 3-state output enable (OE) controlling Y = A logic function. All channels share a common VCC and GND, and inputs are standard CMOS with high impedance and ≤10 pF input capacitance.

Each buffer features balanced CMOS 3-state outputs capable of sourcing/sinking ≥6 mA at 4.5 V while maintaining VOH ≥ 3.98 V and VOL ≤ 0.33 V. The device uses clamp diodes on all I/O pins and complies with HCMOS electrical standards for noise immunity and fanout stability.

Key Specifications

Pinout & Package

SN74HC126DT is housed in a 14-pin SOIC (D) package measuring 8.70 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads compatible with automated SMT assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT126DR and 74LVC126APW, SN74HC126DT provides the broadest supply voltage range and industrial temperature support in SOIC packaging - making it the most versatile choice for general-purpose 3-state buffering where voltage adaptability and legacy footprint compatibility are prioritized over ultra-low power or sub-5 ns speed.

Availability

SN74HC126DT is available at Aetrix Electronics and suitable for industrial control systems, test instrumentation, and legacy interface modules requiring stable component supply and long-term obsolescence management.

Supply support for SN74HC126DT 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 decades of experience in high-reliability industrial and automotive IC design.

The SN74HC126DT belongs to TI's HC (High-Speed CMOS) logic family, engineered for low-power, wide-supply-voltage digital interfacing in cost-sensitive and thermally constrained applications.

FAQ

What is the maximum capacitive load SN74HC126DT can drive while meeting datasheet timing specs?

SN74HC126DT is characterized for CL ≤ 50 pF in switching specifications, with typical propagation delay of 11 ns at 6 V. Driving loads up to 70 pF is feasible per application guidance, but exceeding 50 pF increases tpd and transition time - verified in Table 6.6. For reliable timing closure in high-speed designs, keep total net capacitance (trace + receiver input) ≤ 50 pF. SN74HC126DT's 10 pF input capacitance contributes minimally to upstream loading.

Can SN74HC126DT operate reliably at 3.3 V supply voltage?

Yes, SN74HC126DT is fully specified from 2 V to 6 V, including 3.3 V operation. At VCC = 3.3 V, VOH ≥ 3.15 V (VIH min) and VOL ≤ 0.33 V meet standard 3.3 V CMOS logic thresholds. Propagation delay is ~17 ns (typ) at 3.3 V, CL = 50 pF. SN74HC126DT maintains full functionality and fanout capability across this range without derating.

How should unused inputs and outputs be handled on SN74HC126DT?

Unused inputs on SN74HC126DT must be terminated to VCC or GND - floating inputs cause undefined logic states and increased ICC. Unused outputs may be left unconnected (floating) since they present high impedance when disabled. Do not tie outputs directly to VCC or GND. For OE pins not in use, connect to GND to keep associated buffers enabled, or to VCC to disable them - both are valid per functional table. SN74HC126DT's internal structure tolerates either configuration.

Is SN74HC126DT pin-compatible with other packages in the same family?

Yes, all 14-pin variants of SN74HC126 - including SN74HC126DB (SSOP), SN74HC126N (PDIP), and SN74HC126PW (TSSOP) - share identical pinout and logic function. SN74HC126DT (SOIC) matches the D-package pin assignment shown in Figure 5-1. This allows drop-in replacement across SOIC, SSOP, PDIP, and TSSOP footprints when board layout permits mechanical fit. SN74HC126DT's 8.70 mm × 3.90 mm SOIC body is industry-standard.

Does SN74HC126DT support hot-swap or live-insertion applications?

No, SN74HC126DT does not include hot-swap protection circuitry. Its absolute maximum ratings specify VI and VO limits of –0.5 V to VCC + 0.5 V, and IOK = ±20 mA clamp current. Applying VCC before signal inputs, or vice versa, risks latch-up or damage due to back-powering through I/O clamp diodes. For hot-swap use, add series current-limiting resistors and ensure strict power sequencing - SN74HC126DT itself is not rated for uncontrolled insertion. Always observe TI's recommended power-up sequence: GND → VCC → inputs.