STMicroelectronics M74HCT157B1R

Overview

M74HCT157B1R from STMicroelectronics is a high-speed CMOS quad 2-channel multiplexer with TTL-compatible inputs, 16 ns typical propagation delay at 4.5 V, 4 µA max quiescent current at 25°C, and symmetrical 4 mA output drive. It routes A/B data sources to four independent Y outputs under common SELECT and STROBE control, used in digital logic selection, bus arbitration, and address/data path switching in industrial control systems.

For engineers reviewing the M74HCT157B1R datasheet, M74HCT157B1R pinout, M74HCT157B1R application, or M74HCT157B1R equivalent, key selection factors include its DIP-16 package, -55°C to +125°C operating range, 4.5–5.5 V supply tolerance, and guaranteed 0.8 V/2.0 V input thresholds for robust noise margin in mixed-logic environments.

Technical Context

The M74HCT157B1R implements four independent 2:1 digital multiplexers sharing one SELECT line and one active-low STROBE (ST) enable. When ST is high, all Y outputs are forced low regardless of SELECT or input states-enabling synchronous gating across all channels.

Its C2MOS silicon gate process delivers balanced tPLH/tPHL delays (≈16 ns), symmetrical ±4 mA output drive, and integrated ESD protection on all inputs. Input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) ensure reliable interfacing with TTL-family drivers without level-shifting.

Key Specifications

Pinout & Package

Package: Plastic DIP-16 (0.300" wide), JEDEC MS-001, body dimensions 20.0 × 8.5 mm, lead pitch 2.54 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 2:1 multiplexer applications.

Compared with SN74HCT157N and 74VHC157N, the M74HCT157B1R uniquely combines full -55°C to +125°C operation, guaranteed TTL input compatibility, and DIP-16 packaging-making it optimal for legacy industrial upgrades and harsh-environment deployments where reliability trumps raw speed.

Availability

M74HCT157B1R is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, automotive body control modules, legacy system logic upgrades, and automated test equipment requiring stable component supply over long production lifecycles.

Supply support for M74HCT157B1R 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 M74HCT157B1R belongs to ST's legacy HCT logic family, engineered specifically for seamless TTL-to-CMOS migration in industrial control, instrumentation, and telecom infrastructure where reliability, temperature resilience, and pin compatibility are critical.

FAQ

Is M74HCT157B1R compatible with 3.3 V logic inputs?

No. The M74HCT157B1R requires VCC = 4.5–5.5 V and has VIH minimum of 2.0 V, but its input thresholds are optimized for 5 V TTL compatibility. Driving it with 3.3 V logic may result in marginal or unreliable high-level recognition, especially over temperature and voltage extremes. Use level translators or 74VHC157 for native 3.3 V interfaces.

What happens when STROBE is high?

When STROBE (pin 15) is high, all four Y outputs (pins 4,7,9,12) are forced low regardless of the state of SELECT or the A/B inputs. This provides synchronous blanking of all multiplexer outputs, useful for glitch-free bus arbitration or timed signal gating in real-time control loops.

Does M74HCT157B1R require external pull-up or pull-down resistors?

No. All inputs have internal protection diodes and defined logic thresholds; no external biasing is needed for normal operation. However, floating inputs must be avoided-unconnected A/B/SELECT/STROBE pins should be tied to VCC or GND to prevent undefined output states and increased ICC due to input leakage.

Can M74HCT157B1R drive LED indicators directly?

Yes, within limits. With IOL = 4 mA min at VOL ≤ 0.4 V, it can sink up to ~3 mA through a 1 kΩ current-limiting resistor at 5 V supply-sufficient for low-current indicator LEDs. For higher brightness or multiple LEDs, add a transistor buffer to avoid exceeding output current ratings or degrading VOL.