Texas Instruments SN74AHCT157NSR

Overview

SN74AHCT157NSR from Texas Instruments is a quadruple 2-line to 1-line data selector/multiplexer IC designed for automotive-grade logic routing in 4.5V–5.5V systems. It features a common active-low strobe (G), true-data outputs, TTL-voltage-compatible inputs, and delivers 8mA output drive at V_CC = 5V. It is used in digital bus arbitration, signal path selection, and address/data multiplexing in engine control units and body electronics.

For engineers reviewing the SN74AHCT157NSR datasheet, SN74AHCT157NSR pinout, SN74AHCT157NSR application, or SN74AHCT157NSR equivalent, this page provides verified functional modes, switching characteristics (t_PLH/t_PHL ≤ 9.5 ns @ CL = 15pF), thermal resistance (R_θJA = 64°C/W), latch-up immunity (>250 mA), and TSSOP-16 package details - all confirmed from TI's SCLS347L production datasheet (April 2024).

Technical Context

The SN74AHCT157NSR implements four independent 2:1 multiplexers sharing one active-low strobe input (G). When G is high, all Y outputs are forced low regardless of A/B or data inputs; when G is low, each Y channel selects either its A or B input based on the common A/B select line. Its positive-logic function table defines deterministic output states for all valid input combinations.

It uses advanced CMOS technology with TTL-compatible input thresholds (V_IL = 0.8V, V_VIH = 2.0V) and rail-to-rail output swing (V_OL = 0.44V @ I_OL = 8mA, V_OH = 3.8V @ I_OH = –8mA). Switching performance is characterized at 5V ±0.5V with load capacitance up to 50pF, supporting reliable timing in synchronous digital subsystems.

Key Specifications

Pinout & Package

TSSOP-16 (PW) package: 5.0 mm × 6.4 mm body, 1.2 mm max height, lead pitch 0.65 mm, RoHS-compliant NiPdAu finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHCT157DR and SN74LVC157APWR, the SN74AHCT157NSR uniquely combines AEC-Q100 qualification, 5V operation, TTL compatibility, and compact TSSOP packaging - making it the sole drop-in solution for space-limited, safety-critical 5V automotive multiplexing where thermal efficiency and reliability are prioritized over general-purpose voltage flexibility.

Availability

SN74AHCT157NSR is available at Aetrix Electronics and suitable for automotive engine control units, instrument cluster displays, and body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74AHCT157NSR 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 automotive electronics, with decades of experience in high-reliability logic and interface solutions.

The SN74AHCT157NSR belongs to TI's automotive-qualified AHCT logic family, engineered specifically for robust 5V signal routing in harsh-temperature vehicle subsystems where noise immunity, latch-up resistance, and long-term stability are critical.

FAQ

What is the maximum operating frequency supported by the SN74AHCT157NSR?

The SN74AHCT157NSR does not specify a maximum clock frequency, but its typical propagation delay is 7.5 ns (t_PLH/t_PHL) at CL = 15pF and V_CC = 5V. This supports reliable operation in data paths toggling up to ~70 MHz under controlled loading conditions. For precise timing closure, designers must verify setup/hold margins using the device's published switching characteristics in their specific layout.

Does the SN74AHCT157NSR require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs of the SN74AHCT157NSR must be held at V_CC or GND to prevent floating states that cause increased ICC, noise susceptibility, or undefined outputs. TI explicitly recommends tying unused A/B, G, or data inputs to a valid logic level; leaving them unconnected violates recommended operating conditions and risks erratic behavior in automotive environments.

Is the SN74AHCT157NSR pin-compatible with the SN74AHCT157N (PDIP package)?

Yes - the SN74AHCT157NSR (TSSOP-16) and SN74AHCT157N (PDIP-16) share identical pin numbering, pin functions, and logic behavior per TI's SCLS347L datasheet. However, due to differing package dimensions and thermal characteristics, PCB layout and thermal design must be re-validated when substituting packages.

What is the purpose of the A/B pin on the SN74AHCT157NSR?

The A/B pin is a common address select input that determines which data source (A or B) is routed to all four Y outputs. When A/B = LOW, the 1A–4A inputs are selected; when A/B = HIGH, the 1B–4B inputs are selected. This single control line synchronizes selection across all four multiplexer channels, enabling coordinated data path switching.

Can the SN74AHCT157NSR operate reliably at 4.5V supply voltage?

Yes - the SN74AHCT157NSR is fully specified from 4.5V to 5.5V per its Recommended Operating Conditions table. At V_CC = 4.5V, it maintains guaranteed VOL ≤ 0.44V (I_OL = 8mA), VOH ≥ 3.8V (I_OH = –8mA), and t_PLH/t_PHL ≤ 10 ns, ensuring interoperability with other 5V logic families even at the lower rail limit.