Texas Instruments SN74AHCT157NSRE4

Overview

SN74AHCT157NSRE4 from Texas Instruments is a quadruple 2-line to 1-line data selector/multiplexer IC designed for 4.5V–5.5V V_CC operation in automotive and industrial logic systems. It features a common active-low strobe (G) input, true-data outputs, TTL-voltage-compatible inputs, and delivers 8mA output drive capability at V_CC = 5V. It routes one of two 4-bit input words to four outputs based on the A/B select line.

For engineers reviewing the SN74AHCT157NSRE4 datasheet, SN74AHCT157NSRE4 pinout, SN74AHCT157NSRE4 application, or SN74AHCT157NSRE4 equivalent, this page provides verified functional modes, switching characteristics (t_PLH/t_PHL ≤ 9.5ns @ CL = 15pF), absolute maximum ratings, thermal resistance (R_θJA = 64°C/W), and package-specific layout guidance for NS (SOIC-16) implementation.

Technical Context

The SN74AHCT157NSRE4 implements positive-logic multiplexing with independent channel enable via a shared active-low strobe (G). When G is high, all Y outputs are forced low regardless of A/B or data inputs; when G is low, each Y_n passes either A_n or B_n based on the A/B select signal.

Its CMOS design ensures TTL-compatible input thresholds (V_IL = 0.8V, V_IH = 2.0V), rail-to-rail output swing (V_OL ≤ 0.44V @ I_OL = 8mA, V_OH ≥ 3.8V @ I_OH = –8mA), and latch-up immunity exceeding 250mA per JESD17 - critical for noise-prone automotive environments.

Key Specifications

Pinout & Package

The SN74AHCT157NSRE4 is packaged in a 16-pin SOIC (NS) body measuring 5mm × 4.4mm (body size) with 5mm × 6.4mm overall footprint. Pin 1 is located at the top-left corner adjacent to the index notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHCT157PWR and SN74LVC157APWRE4, the SN74AHCT157NSRE4 uniquely combines 5V TTL compatibility, SOIC-16 manufacturability, and 64°C/W thermal performance - making it optimal for cost-sensitive, thermally stable 5V industrial controls where pin compatibility and legacy interface assurance are mandatory.

Availability

SN74AHCT157NSRE4 is available at Aetrix Electronics and suitable for automotive body control units, industrial PLC I/O expansion modules, and test equipment signal routing requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.

Supply support for SN74AHCT157NSRE4 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 over 90 years of innovation in high-reliability electronics.

The SN74AHCT logic family was engineered for robust 5V system interfacing - delivering TTL-compatible inputs, rail-to-rail outputs, and enhanced latch-up immunity specifically for automotive and industrial control applications.

FAQ

What is the function of the G (strobe) pin on the SN74AHCT157NSRE4?

The G pin is an active-low strobe that globally disables all four outputs: when G = HIGH, all Y outputs are forced LOW regardless of A/B select or input states; when G = LOW, the device performs normal 2:1 multiplexing. This enables synchronized data gating in timing-critical systems like PLC scan cycles or automotive diagnostic modes - a key feature distinguishing SN74AHCT157NSRE4 from non-strobed multiplexers.

Does the SN74AHCT157NSRE4 support mixed-voltage operation between 3.3V and 5V logic domains?

No - the SN74AHCT157NSRE4 operates strictly at V_CC = 4.5V to 5.5V and features TTL-compatible inputs (V_IL = 0.8V, V_IH = 2.0V), making it ideal for 5V-only systems. It does not support 3.3V V_CC or translate 3.3V inputs safely; for mixed-voltage interfaces, use SN74LVC157A with appropriate level-shifting or dual-supply translators alongside SN74AHCT157NSRE4.

What is the maximum capacitive load the SN74AHCT157NSRE4 can drive while maintaining specified t_PLH/t_PHL?

The SN74AHCT157NSRE4 is characterized for CL = 15pF (t_PLH/t_PHL ≤ 9.5ns) and CL = 50pF (t_PLH/t_PHL ≤ 12ns) at V_CC = 5V. Driving >50pF increases propagation delay nonlinearly and may cause timing violations in high-speed data paths; for heavier loads, add a 74AHCT buffer stage or reduce trace length/capacitance per the SN74AHCT157NSRE4 layout guidelines.

How does the SN74AHCT157NSRE4 handle unused inputs, and why does it matter?

All unused inputs on the SN74AHCT157NSRE4 must be tied to V_CC or GND - floating inputs cause undefined output states, increased ICC, and potential oscillation due to CMOS input structure. TI explicitly mandates this in Section 4.2; leaving A/B, G, or any data input unconnected risks erratic behavior in automotive or industrial environments where EMI could induce false transitions - a failure mode documented in TI application report SCBA004.

Is the SN74AHCT157NSRE4 pin-compatible with older 74LS157 or 74F157 devices?

Yes - the SN74AHCT157NSRE4 uses identical pinout (SOIC-16 NS package) and logic function as 74LS157 and 74F157, but with CMOS benefits: lower ICC (<20μA vs. ~19mA for 74LS), higher noise immunity, and rail-to-rail outputs. It is a direct drop-in replacement for those families in 5V systems, provided timing margins accommodate its faster propagation (9.5ns vs. 15–20ns for LS/F series) and output drive strength (±8mA vs. ±8mA LS, ±20mA F).