STMicroelectronics M74HC251TTR

Overview

M74HC251TTR from STMicroelectronics is a high-speed CMOS 8-channel 3-state multiplexer with true (Y) and complement (W) outputs, STROBE-enabled output control, symmetrical 4 mA drive capability, 17 ns typical propagation delay at 6 V, and operation across 2–6 V supply. It routes one of eight digital inputs to dual complementary outputs in industrial control logic and data-path selection.

For engineers reviewing the M74HC251TTR datasheet, M74HC251TTR pinout, M74HC251TTR application, or M74HC251TTR equivalent, key selection criteria include 3-state enable timing (tPZL/tPLZ), input noise immunity (28% VCC), balanced tPLH/tPHL delays, wide temperature range (−55°C to +125°C), and TSSOP-16 package compatibility with PCB space-constrained designs.

Technical Context

The M74HC251TTR implements an 8:1 multiplexer using silicon gate C2MOS technology, supporting address decoding via three select lines (A, B, C) and enabling/disabling both Y and W outputs simultaneously through a single active-low STROBE input. Its dual-output architecture provides complementary logic states without external inverters.

It features rail-to-rail input voltage tolerance (0 to VCC), guaranteed 4 mA sink/source drive strength at 4.5 V and 6 V, and high-impedance leakage current ≤10 µA over full temperature range. Propagation delays are balanced (tPLH ≅ tPHL) and specified under CL = 50 pF load with 6 ns input edge rates.

Key Specifications

Pinout & Package

TSSOP-16 package: 4.4 mm × 5.0 mm body, 0.65 mm pitch, thin-profile surface-mount design optimized for automated assembly and thermal performance in dense layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-channel 3-state multiplexer applications.

Compared with SN74HC251PWR and 74VHC251FT, the M74HC251TTR delivers superior thermal ruggedness (−55°C to +125°C), lower quiescent current at high temperature, and tighter output symmetry-making it optimal for mission-critical embedded systems where reliability outweighs marginal speed gains.

Availability

M74HC251TTR is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, automotive body control modules, automated test equipment signal routing, and medical infusion pump logic requiring stable component supply across extended temperature and long product lifecycles.

Supply support for M74HC251TTR 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, designing and manufacturing microcontrollers, power management ICs, sensors, and analog/mixed-signal devices for industrial, automotive, and consumer markets.

The M74HC251TTR belongs to ST's high-reliability HC logic family, engineered specifically for robust operation in harsh environments-including factory automation, vehicle electronics, and safety-critical medical instrumentation-where consistent timing, low power, and wide temperature compliance are non-negotiable.

FAQ

What is the maximum clock frequency supported by M74HC251TTR in a data-select application?

The M74HC251TTR does not operate on a clock signal-it is combinational logic. Its usable data rate depends on propagation delay and load capacitance. With CL = 50 pF and VCC = 6 V, tPD = 22 ns (max), supporting reliable operation up to ~20 MHz for clean edge-triggered sampling in synchronous systems.

Can M74HC251TTR interface directly with 3.3 V microcontrollers?

Yes. With VCC = 3.3 V, VIH = 2.31 V (min) and VIL = 1.09 V (max), the M74HC251TTR meets 3.3 V LVTTL input thresholds. Its outputs swing rail-to-rail, delivering VOH ≥ 3.15 V and VOL ≤ 0.4 V at 4 mA load-compatible with standard 3.3 V CMOS inputs.

Does the STROBE pin support partial output disabling (e.g., only Y or only W)?

No. STROBE is a global 3-state enable: when high, both Y and W enter high-impedance simultaneously. There is no independent control for Y or W. This ensures atomic bus release and prevents metastability during state transitions in shared-data-path architectures.

Is M74HC251TTR pin-compatible with older 74LS251 in DIP-16 packages?

Functionally identical and pin-compatible with 74LS251 in logic behavior and pin assignment, but not electrically compatible due to differing voltage thresholds, drive strength, and supply range. Direct replacement requires verifying VCC (2–6 V vs. 4.75–5.25 V), noise margins, and fan-out loading in the target circuit.