Texas Instruments SN74AS151N

Overview

SN74AS151N from Texas Instruments is a TTL-compatible 8-line to 1-line data selector/multiplexer with active-low strobe (G), dual complementary outputs (Y and W), and operation over 0°C to 70°C. It delivers 48 mA low-level output drive, 15 mA high-level sink capability, and propagation delays as low as 1 ns (G→W tPHL) at VCC = 5 V. It serves in digital logic systems requiring fast, deterministic signal routing - such as address decoding in microprocessor peripherals.

For engineers reviewing the SN74AS151N datasheet, SN74AS151N pinout, SN74AS151N application, or SN74AS151N equivalent, key selection criteria include its 16-pin PDIP package, dual-output logic behavior (Y = selected input, W = inverted Y), guaranteed 48 mA IOL, and compatibility with standard 5-V TTL bus loading requirements.

Technical Context

The SN74AS151N implements full binary decoding of three select inputs (A, B, C) to route one of eight data inputs (D0–D7) to the true output Y, while simultaneously providing the complement on W. Its strobe (G) input enables or disables both outputs: G = HIGH forces Y = LOW and W = HIGH regardless of select or data states.

Designed using advanced Schottky-clamped bipolar technology, it achieves higher speed and lower power-delay product than earlier 74LS/74ALS variants. Input clamping diodes are integrated to simplify system-level transient protection, and all inputs tolerate up to 7 V independent of VCC.

Key Specifications

Pinout & Package

SN74AS151N is supplied in a 16-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard through-hole footprint and 0.1-inch pin pitch. Pin 1 is marked by a notch or dot at the top-left corner when viewed from the top with pins facing downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ALS151N and SN74F151N, the SN74AS151N uniquely combines sub-12 ns propagation, 48 mA output drive, and full 5-V TTL compatibility - making it the only option among the three capable of driving 10+ TTL loads while meeting <15 ns system timing budgets.

Availability

SN74AS151N is available at Aetrix Electronics and suitable for microprocessor address decoding, parallel-to-serial conversion, Boolean function generation, and test equipment signal routing requiring stable component supply and long-term obsolescence management.

Supply support for SN74AS151N 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 ICs with broad industrial, automotive, and communications reach.

The SN74AS151N belongs to TI's 74AS logic family - engineered for high-speed, low-power bipolar TTL applications where propagation delay and output drive are critical, especially in legacy computing and instrumentation systems.

FAQ

What logic family does SN74AS151N belong to, and how does it differ from 74LS or 74ALS variants?

The SN74AS151N belongs to the 74AS (Advanced Schottky) logic family. Compared to 74LS, it offers significantly faster propagation delays (e.g., 1.5 ns G→W tPLH vs. >20 ns for LS) and higher output drive (48 mA vs. 8 mA). Versus 74ALS, it doubles the low-level output current and reduces delays by ~40%, while maintaining pin compatibility and identical truth table behavior. The SN74AS151N retains full 5-V TTL voltage thresholds and operates within the same 0°C to 70°C range.

Does SN74AS151N require external pull-up resistors on its outputs?

No, SN74AS151N does not require external pull-up resistors on Y or W outputs. Its totem-pole output structure actively drives both HIGH and LOW states, delivering −15 mA IOH and 48 mA IOL under recommended operating conditions. Pull-ups would interfere with defined logic levels and increase power consumption unnecessarily. External termination is only needed if driving long traces or unterminated transmission lines.

Can SN74AS151N interface directly with 3.3 V logic devices?

Yes, SN74AS151N can safely receive 3.3 V logic inputs: its VIH threshold is 2.0 V and VIL is 0.8 V, well within 3.3 V CMOS logic swing. However, its 5 V outputs exceed 3.3 V input absolute maximum ratings for most 3.3 V devices. To avoid damage, use a level-shifting buffer or resistor divider on Y/W outputs when driving 3.3 V inputs. The SN74AS151N itself remains fully functional with 5 V supply only.

What is the purpose of the W output on SN74AS151N, and is it always the inverse of Y?

The W output on SN74AS151N is the logical complement of Y and is guaranteed to be inverted under all enabled conditions (G = LOW). When G = HIGH, W is forced HIGH and Y is forced LOW - preserving their complementary relationship even during disable. This dual-output architecture eliminates external inverters in applications needing both polarities, such as differential bus drivers or synchronous latch control, and is explicitly confirmed in the device's function table and logic diagram.

Is SN74AS151N RoHS compliant, and what is its lead finish?

Yes, SN74AS151N is RoHS compliant (lead-free). Per TI's packaging documentation, its PDIP (N) package uses NiPdAu (nickel-palladium-gold) lead finish, also referred to as NIPDAU. This finish meets JEDEC J-STD-020 moisture sensitivity Level-1 requirements and supports standard SnPb or lead-free reflow profiles. The part marking "SN74AS151N" appears directly on the package body.