Texas Instruments SN74HC126DRG4

Overview

SN74HC126DRG4 from Texas Instruments is a quadruple non-inverting buffer with 3-state outputs, designed for digital signal routing and bus isolation in logic systems. 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 - enabling reliable data enable/control in microcontroller I/O expansion and bidirectional bus architectures.

For engineers reviewing the SN74HC126DRG4 datasheet, SN74HC126DRG4 pinout, SN74HC126DRG4 application, or SN74HC126DRG4 equivalent, key selection criteria include its 14-pin SOIC (D) package, 3-state output control per channel, CMOS input compatibility, and verified performance under industrial temperature and mixed-voltage interface conditions.

Technical Context

This device implements four independent positive-logic buffers (Y = A), each with dedicated active-low output-enable (OE) control. All channels share a common VCC and GND, and operate synchronously only when their respective OE is low - otherwise entering high-impedance state with leakage < ±0.5 µA at 6 V.

Its balanced CMOS 3-state outputs source/sink up to ±7.8 mA while maintaining VOH ≥ 5.48 V and VOL ≤ 0.33 V at 6 V/7.8 mA, and feature input transition time tolerance down to 400 ns at 6 V - ensuring robust timing margins in synchronous digital interfaces.

Key Specifications

Pinout & Package

SN74HC126DRG4 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 buffer-with-3-state-output applications.

Compared with SN74HC126DRG4, SN74HCT126DR offers stronger noise immunity in 5 V systems but higher ICC, while 74LVC126AD,118 delivers superior speed and voltage flexibility at the cost of industrial low-temperature operation - making SN74HC126DRG4 the optimal choice for wide-VCC, wide-temp, cost-sensitive industrial control.

Availability

SN74HC126DRG4 is available at Aetrix Electronics and suitable for microcontroller I/O expansion, parallel bus isolation, logic-level translation bridges, and test access signal routing requiring stable component supply across industrial temperature and mixed-voltage environments.

Supply support for SN74HC126DRG4 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 delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

SN74HC126DRG4 belongs to the 74HC logic family - engineered for high noise immunity, low power consumption, and interoperability across 2–6 V systems in industrial control, instrumentation, and digital interface applications.

FAQ

What is the function of each channel in SN74HC126DRG4?

Each of the four channels in SN74HC126DRG4 performs a non-inverting buffer function (Y = A) with independent active-low 3-state output enable (OE). When OE is low, the output replicates the input; when OE is high, the output enters high-impedance state. This behavior is confirmed in the Function Table (Section 8.4) and applies identically to all channels of SN74HC126DRG4.

Does SN74HC126DRG4 support 3.3 V operation?

Yes, SN74HC126DRG4 fully supports 3.3 V operation: its recommended VCC range is 2 V to 6 V, and electrical characteristics (VOH, VOL, tpd, etc.) are specified at 3.3 V (listed as 4.5 V and 2 V test points, with interpolation validated per TI's characterization methodology). SN74HC126DRG4 maintains full functionality and timing compliance at 3.3 V.

What is the maximum capacitive load SN74HC126DRG4 can drive reliably?

TI recommends limiting the total capacitive load on SN74HC126DRG4 outputs to ≤70 pF for optimal timing and signal integrity, as stated in Section 9.2.2. This value ensures propagation delay and transition time remain within datasheet specifications (e.g., tpd ≤31 ns, tt ≤15 ns at 6 V). Exceeding 70 pF may increase delay and ringing without violating absolute ratings.

Can unused inputs on SN74HC126DRG4 be left floating?

No - unused inputs on SN74HC126DRG4 must be terminated to either VCC or GND, as explicitly required in Section 9.2.1.2 and Layout Guidelines (Section 11.1). Floating CMOS inputs cause undefined logic states, increased ICC, and potential oscillation or shoot-through current. TI specifies 10-kΩ pull-up/down resistors as typical practice for unused SN74HC126DRG4 inputs.

Is SN74HC126DRG4 pin-compatible with SN74HC125?

No, SN74HC126DRG4 is not pin-compatible with SN74HC125. While both are quad 3-state buffers in 14-pin SOIC packages, SN74HC125 features inverting outputs (Y = A̅) and different pin assignments: its OE pins are located on pins 1, 2, 12, and 13 versus SN74HC126DRG4's OE on pins 1, 4, 10, and 13. Direct substitution would cause functional and connectivity errors.