Texas Instruments SN74AS850AFN

Overview

SN74AS850AFN from Texas Instruments is a 4-line-to-1-line 1-of-16 data selector/multiplexer with clock-controlled select register, dual complementary 3-state outputs (Y and W), and independent output controls (G, GY, GW). It operates at 5 V, supports up to 60 MHz clock frequency, and delivers ±48 mA output drive for bus-oriented systems.

For engineers reviewing the SN74AS850AFN datasheet, SN74AS850AFN pinout, SN74AS850AFN application, or SN74AS850AFN equivalent, this device is selected for high-speed data routing in legacy TTL-compatible digital systems requiring cascaded multiplexing, Boolean function generation, or parallel-to-serial conversion with precise timing control via CLK.

Technical Context

The SN74AS850AFN implements a synchronous 16-input multiplexer architecture where S0–S3 select lines are latched on the rising edge of CLK, ensuring symmetrical setup/hold timing (tsu = 10 ns, th = 0 ns) and eliminating glitches during select transitions. Its internal decoder drives two complementary outputs - Y (true) and W (inverted) - each independently controllable via GY and GW.

Output enable logic is fully buffered: master control G disables both outputs simultaneously, while GY and GW allow per-output 3-state management without affecting internal decoding or latch operation. This enables concurrent data loading and bus release - new D0–D15 values may be set while outputs remain in high-impedance state.

Key Specifications

Pinout & Package

SN74AS850AFN is housed in a 28-pin PLCC (Plastic Leaded Chip Carrier) package with J-leads, measuring 11.43 mm × 11.43 mm, designed for surface-mount assembly and thermal reliability in dense PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1-of-16 multiplexer applications.

Compared with SN74AS851BN, SN74AS850AFN provides deterministic clock-aligned selection critical for synchronous digital systems, while SN74F540N lacks any multiplexing capability - making it unsuitable for data routing tasks despite shared 28-pin PDIP footprint.

Availability

SN74AS850AFN is available at Aetrix Electronics and suitable for legacy system repair, military avionics sustainment, industrial controller refurbishment, and educational lab instrumentation requiring stable component supply despite its obsolete status.

Supply support for SN74AS850AFN 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 leader founded in 1930, delivering analog and embedded processing solutions with emphasis on reliability, longevity, and broad industry support.

The SN74AS850AFN belongs to TI's Advanced Schottky (AS) TTL logic family, engineered for high-speed commercial applications requiring robust noise immunity, consistent propagation delay, and direct compatibility with legacy 5 V digital systems.

FAQ

What is the primary function of the SN74AS850AFN in digital systems?

The SN74AS850AFN functions as a 1-of-16 data selector/multiplexer with clocked select inputs and dual 3-state outputs. It routes one of 16 data inputs (D0–D15) to complementary outputs Y and W based on synchronous S0–S3 address bits sampled on the rising edge of CLK. Its design enables precise timing control in bus-oriented and logic-generation applications where deterministic data selection is required - a core capability confirmed in the SDAS154A datasheet.

Does the SN74AS850AFN support cascading for larger multiplexer configurations?

Yes, the SN74AS850AFN supports cascading to build 1-of-32, 1-of-64, or larger multiplexers. Its G (master output control), Y, and W outputs are explicitly designed for hierarchical connection - for example, upper-stage Y/W can drive lower-stage G inputs while sharing CLK. Figures 2 and 3 in the SDAS154A datasheet demonstrate validated 1-of-32 and 1-of-64 implementations using multiple SN74AS850AFN units.

What are the key timing parameters that define the SN74AS850AFN's performance in synchronous designs?

Key timing parameters include: maximum clock frequency of 60 MHz; setup time (tsu) of 10 ns for S0–S3 before CLK↑; hold time (th) of 0 ns; and propagation delays ranging from 3 ns (D to W) to 17.5 ns (CLK to Y). These values - specified in the "Switching Characteristics" table of the SDAS154A datasheet - ensure reliable operation in high-speed TTL-compatible systems with tight timing budgets.

How does the 3-state output architecture of the SN74AS850AFN benefit bus-based designs?

The SN74AS850AFN features three independent 3-state controls: G (global), GY (Y-output only), and GW (W-output only). When asserted, these place Y and/or W into high-impedance mode, removing load from shared bus lines without disrupting internal decoding or data latching. This allows safe bus sharing, concurrent data preloading, and elimination of external pull-up components - directly enabling clean bus-organized system architectures as described in the "Technical Context" section of the datasheet.

Is the SN74AS850AFN pin-compatible with the SN74AS851B, and what is the main functional distinction?

Yes, SN74AS850AFN and SN74AS851B share identical pinouts, packages, DC electrical characteristics, and thermal ratings. The sole functional distinction is select-register control: SN74AS850AFN uses a clocked register (CLK-triggered), while SN74AS851B uses an enable-controlled register (SC-triggered). This difference affects timing behavior - SN74AS850AFN provides synchronous, edge-aligned selection; SN74AS851B offers asynchronous, level-sensitive selection - as documented in the FUNCTION TABLE and logic diagrams of the SDAS154A datasheet.