Texas Instruments SN74AS151NSR

Overview

SN74AS151NSR from Texas Instruments is a high-speed 8-line to 1-line data selector/multiplexer with active-low enable (G), complementary outputs (Y and W), and TTL-compatible inputs/outputs. It operates from 4.5 V to 5.5 V at 0°C to 70°C, delivers 48 mA low-level output drive, and achieves propagation delays as low as 1 ns (G→W tPHL). It is used in digital logic systems for data routing, Boolean function generation, and parallel-to-serial conversion.

For engineers reviewing the SN74AS151NSR datasheet, SN74AS151NSR pinout, SN74AS151NSR application, or SN74AS151NSR equivalent, key selection criteria include its 16-pin SOP (NS) package, 4.5–5.5 V supply range, 48 mA IOL capability, sub-15 ns worst-case propagation delay, and compatibility with standard TTL logic families in industrial control and legacy computing interfaces.

Technical Context

The SN74AS151NSR implements full binary decoding of three select lines (A, B, C) to route one of eight data inputs (D0–D7) to the true output (Y), while the complement appears at W. The strobe input (G) enables operation only when low; a high G forces Y low and W high - enabling wired-OR expansion and cascading.

Its AS (Advanced Schottky) logic family delivers higher speed and greater drive strength than ALS variants: tPHL/tPLH from G to W is as low as 1 ns and 1.5 ns respectively, and it sustains 48 mA sink current at VOL ≤ 0.5 V, supporting direct interface to LEDs, relays, or bus loads without external buffers.

Key Specifications

Pinout & Package

SOP-16 (NS package), 2000-piece tape-and-reel, 10.4 mm × 5.3 mm body, 1.27 mm pitch, 2.00 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8:1 multiplexer applications.

Compared with SN74ALS151NSR and 74HC151PW, the SN74AS151NSR uniquely balances high-speed TTL compatibility, robust 48 mA output drive, and integrated input protection - making it optimal for industrial control, test equipment, and legacy 5 V logic interfacing where timing precision and load driving matter.

Availability

SN74AS151NSR is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, digital test equipment multiplexing, and legacy computer bus arbitration requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74AS151NSR 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74AS151NSR belongs to TI's legacy TTL logic portfolio, designed specifically for high-reliability, high-speed digital signal routing in industrial control, instrumentation, and retro-computing applications where robustness and timing predictability are critical.

FAQ

What is the maximum operating frequency supported by the SN74AS151NSR?

The SN74AS151NSR does not specify a maximum clock frequency, but its worst-case propagation delay (G→Y) is 11 ns. This supports reliable operation in synchronous systems with clock periods ≥ 22 ns - corresponding to a theoretical upper limit near 45 MHz for gated data paths. Actual usable frequency depends on board layout, load capacitance, and setup/hold timing margins in the host system. The SN74AS151NSR is commonly deployed in 20–30 MHz digital control and test applications.

Can the SN74AS151NSR drive LEDs directly without a current-limiting resistor?

No, the SN74AS151NSR cannot safely drive LEDs without an external current-limiting resistor. Although it provides 48 mA sink capability, forward voltage and dynamic characteristics of LEDs vary widely. A series resistor is mandatory to limit current to a safe value (e.g., 10–20 mA) and prevent damage to both the LED and the SN74AS151NSR output stage. Typical designs use a 220 Ω resistor with a 5 V supply and red LED (VF ≈ 1.8 V) to achieve ~14.5 mA.

Is the SN74AS151NSR pin-compatible with the SN74ALS151NSR?

Yes, the SN74AS151NSR is pin-compatible with the SN74ALS151NSR: both use the same 16-pin SOP (NS) package, identical pin assignments (D0–D7, A–C, G, Y, W, VCC, GND), and share the same footprint and solder mask layout. However, they differ electrically - the SN74AS151NSR offers faster propagation delays, higher output drive, and tighter VOL spec. No PCB changes are required when upgrading from SN74ALS151NSR to SN74AS151NSR in existing designs.

Does the SN74AS151NSR have built-in ESD protection on its inputs?

The SN74AS151NSR includes internal input clamp diodes to VCC and GND, providing basic transient suppression for moderate ESD events (per ANSI/ESDA-JEDEC JS-001 Class 2, ~2 kV HBM). However, it lacks dedicated ESD protection structures beyond these clamps. For harsh industrial environments or connector-facing circuits, external TVS diodes or series resistors are recommended. The clamp diodes simplify system-level protection but do not replace full IEC 61000-4-2 compliance measures.

What is the purpose of the W output on the SN74AS151NSR?

The W output on the SN74AS151NSR is the logical complement of the Y output - when Y is high, W is low, and vice versa. This dual-output architecture enables direct implementation of wired-AND logic, differential signaling, or inverted control paths without external inverters. In applications like bus arbitration or fault-tolerant voting logic, W provides immediate access to the inverse signal, reducing propagation delay and component count compared to adding a separate inverter stage.