STMicroelectronics M74HC126TTR

Overview

M74HC126TTR from STMicroelectronics is a high-speed CMOS quad 3-state bus buffer with symmetrical output drive (±6 mA), 8 ns typical propagation delay at 6 V, and 2–6 V wide supply range. It functions as a bidirectional data isolator in digital bus systems, enabling controlled signal routing in microcontroller peripheral interfaces, memory address latching, and logic-level translation between mixed-voltage subsystems.

For engineers reviewing the M74HC126TTR datasheet, M74HC126TTR pinout, M74HC126TTR application, or M74HC126TTR equivalent, key selection criteria include 3-state enable timing (tPZL/tPLZ ≤ 19 ns at 6 V), rail-to-rail input thresholds (VIH = 4.2 V min at VCC = 6 V), low quiescent current (ICC ≤ 4 μA), and TSSOP14 thermal performance for space-constrained PCB layouts.

Technical Context

The M74HC126TTR implements four independent non-inverting buffers, each with a dedicated active-high 3-state enable input (G). Output state transitions are fully defined by the truth table: when G = L, Y = A; when G = H, Y = Z (high-impedance). All inputs feature integrated ESD protection (HBM: 2 kV, CDM: 1 kV).

Designed using silicon gate C2MOS technology, it delivers balanced tPLH/tPHL propagation delays (≤19 ns at VCC = 6 V, CL = 50 pF) and matched output impedance (|IOH| = IOL ≥ 6 mA), ensuring minimal skew across all four channels in synchronous bus applications.

Key Specifications

Pinout & Package

TSSOP14 (Thin Shrink Small Outline Package, 14-pin) - 5.0 × 6.4 mm body, 0.65 mm pitch, 1.2 mm max height, JEDEC MO-153 compliant, RoHS-compliant ECOPACK®2.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC126PW and 74LVC126APW, the M74HC126TTR uniquely supports full 2–6 V operation in a thermally efficient TSSOP14 package, making it optimal for mixed-voltage industrial backplanes where supply flexibility and board area are both critical.

Availability

M74HC126TTR is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, medical diagnostic equipment backplanes, and test & measurement instrumentation requiring stable component supply across extended temperature ranges.

Supply support for M74HC126TTR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power ICs, sensors, and analog/mixed-signal devices for industrial, automotive, and consumer markets.

The M74HC126TTR belongs to ST's HC logic family-engineered for high noise immunity, low static power, and seamless interoperability with legacy 74-series logic in space- and power-constrained embedded systems.

FAQ

What is the maximum capacitive load the M74HC126TTR can drive while maintaining specified timing?

The M74HC126TTR is characterized up to 150 pF load capacitance per output, with propagation delay increasing from 13 ns (CL = 50 pF) to 27 ns (CL = 150 pF) at VCC = 6 V. Driving >150 pF risks violating tPLH/tPHL specs and may require series termination or reduced clock frequency to maintain setup/hold margins.

Can the M74HC126TTR be used with a 3.3 V supply while interfacing to 5 V logic?

No-the M74HC126TTR is not 5 V tolerant. At VCC = 3.3 V, absolute maximum input voltage is 3.8 V. Direct connection to 5 V signals risks latch-up or permanent damage. Use a dedicated level translator like the TXB0104 or dual-supply buffer for safe 3.3 V ↔ 5 V interfacing.

Is the M74HC126TTR pin-compatible with the 74HC125?

No-M74HC126TTR has active-high enables (1G–4G), whereas 74HC125 uses active-low enables (1G̅–4G̅). Pin mapping differs: enable pins occupy positions 1, 4, 10, 13 on both, but logic polarity inversion means direct substitution causes functional failure unless external inverters are added.

Does the M74HC126TTR require external pull-up or pull-down resistors on unused inputs?

Yes-unused inputs must be terminated to VCC or GND. Floating CMOS inputs cause increased ICC, erratic switching, and potential shoot-through current. ST recommends ≤10 kΩ pull-up/down resistors; internal input leakage (±0.1 μA) ensures stable logic levels when properly biased.