Texas Instruments SN74ALS137AN

Overview

SN74ALS137AN from Texas Instruments is a 3-line to 8-line decoder/demultiplexer with integrated 3-bit address latch and dual output enables (G1, G2). It operates at 4.5–5.5 V, delivers 4 mA low-level output drive, supports 0°C to 70°C ambient operation, and features glitch-free strobed-address decoding for bus-oriented systems. It is used in memory address decoding and I/O port selection in legacy TTL-based industrial controllers.

For engineers reviewing the SN74ALS137AN datasheet, SN74ALS137AN pinout, SN74ALS137AN application, or SN74ALS137AN equivalent, key selection considerations include latch-enable timing (tsu = 10 ns, th = 5 ns), output enable independence, propagation delays (tPLH/tPHL ≤ 20 ns), and PDIP-16 package compatibility with through-hole prototyping and legacy backplane designs.

Technical Context

The SN74ALS137AN implements positive-logic decoding with latched address inputs (A, B, C) controlled by LE: when LE transitions high, the current address is captured and held regardless of subsequent input changes. Output enables G1 and G2 operate independently-G1 low or G2 high forces all outputs high, enabling hierarchical cascading without external logic.

It uses ALS (Advanced Low-Power Schottky) bipolar technology, delivering TTL-compatible voltage thresholds (VIH = 2 V, VIL = 0.8 V), 11 mA typical ICC at 5.5 V, and guaranteed 4 mA sink capability per output. Its 16-pin PDIP package supports direct replacement of earlier 74LS137 and 74S137 variants in existing PCB layouts where thermal and timing margins allow.

Key Specifications

Pinout & Package

SN74ALS137AN is supplied in a 16-pin plastic dual in-line package (PDIP-N), 300-mil width, with through-hole mounting and industry-standard pin spacing (0.1″). Pin 1 is marked with a notch or dot; pin numbering follows standard DIP convention (counterclockwise from top-left corner).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-to-8 latched decoder applications.

Compared with SN74LS137N, SN74ALS137AN reduces power by ~45% and improves speed by ~40%; compared with SN74AS137N, it trades 35% lower ICC for ~60% longer propagation delay - making it optimal for thermally constrained, medium-speed industrial control applications where reliability and compatibility outweigh peak performance.

Availability

SN74ALS137AN is available at Aetrix Electronics and suitable for memory address decoding, I/O port selection, bus-oriented strobed logic, and legacy industrial control backplane applications requiring stable component supply and long-term obsolescence management.

Supply support for SN74ALS137AN 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 for industrial, automotive, and communications markets.

The SN74ALS137AN belongs to TI's legacy 74ALS logic family, designed specifically for high-reliability, medium-speed digital control systems where power efficiency, noise immunity, and pin compatibility with earlier TTL families were critical design requirements.

FAQ

What is the primary function of the SN74ALS137AN?

The SN74ALS137AN is a 3-line to 8-line decoder/demultiplexer with integrated 3-bit address latch and dual independent output enables (G1, G2). It captures address inputs A, B, C on the rising edge of LE, then decodes them to drive one of eight active-low outputs (Y0–Y7) when enabled. This functionality makes SN74ALS137AN ideal for memory and I/O selection in bus-oriented digital systems where glitch-free, strobed addressing is required.

Is the SN74ALS137AN pin-compatible with the SN74LS137N?

Yes, the SN74ALS137AN is pin-compatible with the SN74LS137N in the 16-pin PDIP package - identical pinout, function mapping, and logic behavior. However, SN74ALS137AN offers lower power consumption (11 mA vs 20 mA typical ICC) and faster propagation delays (≤20 ns vs ≤35 ns), making SN74ALS137AN a direct functional and physical upgrade for existing LS-based designs where thermal or timing margins permit.

What are the absolute maximum ratings for the SN74ALS137AN?

The SN74ALS137AN has an absolute maximum supply voltage (VCC) of 7 V, absolute maximum input voltage (VI) of 7 V, and storage temperature range of −65°C to 150°C. Its operating free-air temperature range is 0°C to 70°C. Exceeding these limits may cause permanent damage; functional operation is only guaranteed within the recommended conditions: VCC = 4.5–5.5 V, TA = 0–70°C. These ratings ensure robustness in commercial industrial environments where transient overvoltage or thermal cycling may occur.

How does the latch-enable (LE) input work on the SN74ALS137AN?

The LE input on the SN74ALS137AN operates on a rising-edge transition: when LE goes from low to high, the current states of address inputs A, B, and C are captured and held in internal latches. Once latched, further changes to A, B, or C are ignored until LE returns low. This allows SN74ALS137AN to maintain stable decoded outputs even if address lines change asynchronously - a key feature for reliable operation in strobed bus architectures where address validity is time-limited.

Can the SN74ALS137AN drive standard TTL inputs directly?

Yes, the SN74ALS137AN can drive standard TTL inputs directly: its guaranteed low-level output voltage (VOL = 0.4 V at IOL = 4 mA) and high-level output voltage (VOH = VCC − 2 V at IOH = −0.4 mA) meet or exceed TTL input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V). With 4 mA sink capability per output, SN74ALS137AN can reliably drive up to 10 standard 74LS inputs or 5 74ALS inputs without external buffering - simplifying interconnect in dense logic designs.