Texas Instruments SN74ALS158NG4

Overview

SN74ALS158NG4 from Texas Instruments is a quad 2-line-to-1-line data selector/multiplexer with inverted output logic, designed for high-speed TTL-compatible digital systems. It features buffered inputs and outputs, 16-pin PDIP (N) package, operates from 4.5 V to 5.5 V, delivers 8 mA low-level output drive, and supports 0°C to 70°C industrial temperature range. It routes one of two 4-bit data sources to four inverted outputs under control of a common strobe (G) and select (A/B) inputs.

For engineers reviewing the SN74ALS158NG4 datasheet, SN74ALS158NG4 pinout, SN74ALS158NG4 application, or SN74ALS158NG4 equivalent, key selection considerations include its inverted-output architecture (vs. true-output SN74ALS157A), propagation delay (tPHL/tPLH ≤ 12 ns at VCC = 5 V), 4.5–5.5 V supply tolerance, and compatibility with legacy 74ALS logic families in bus arbitration and signal routing.

Technical Context

The SN74ALS158NG4 implements a 4-channel, 2:1 multiplexing function using bipolar ALS (Advanced Low-Power Schottky) technology. Each output gate receives inverted data from either input A or B based on the A/B select line, with all outputs enabled or disabled simultaneously by the active-low strobe (G) input. Its internal structure includes inverters and drivers optimized to minimize propagation delay while maintaining TTL voltage thresholds and noise margins.

Unlike the SN74ALS157A, which presents true data, the SN74ALS158NG4's inverted output path eliminates an external inverter stage in applications requiring complemented signals-reducing component count and board area in address/data bus switching, ALU operand selection, and test pattern generation circuits where inversion is functionally required.

Key Specifications

Pinout & Package

SN74ALS158NG4 uses a 16-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard through-hole mounting and 0.1-inch pin pitch. Pin 1 is located at the top-left corner adjacent to the notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ALS157AN (true-output) and SN74AS158N (faster AS variant), SN74ALS158NG4 provides optimal balance of speed, power efficiency, and inverted-output functionality for cost-sensitive industrial control and legacy computing applications where 12 ns delay and 10 mA ICC are acceptable.

Availability

SN74ALS158NG4 is available at Aetrix Electronics and suitable for industrial control panels, legacy computer refurbishment, and test equipment manufacturing requiring stable component supply and long-term obsolescence management.

Supply support for SN74ALS158NG4 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74ALS158NG4 belongs to TI's legacy 74ALS logic family, engineered for backward compatibility with 74TTL systems while delivering improved speed-power trade-offs for mid-1980s digital instrumentation and control applications.

FAQ

What is the output logic polarity of SN74ALS158NG4?

The SN74ALS158NG4 provides inverted output logic: when input A is selected (A/B = L), output Y equals NOT(A); when input B is selected (A/B = H), output Y equals NOT(B). This differs from the SN74ALS157A, which delivers true (non-inverted) outputs. The SN74ALS158NG4's inverted architecture reduces external component count in applications requiring complemented signals, such as certain ALU configurations or test-bus drivers.

Does SN74ALS158NG4 support 3-state outputs?

No, SN74ALS158NG4 does not feature 3-state outputs. Its outputs are push-pull (totem-pole) and always driven - either high or low - when the strobe (G) input is low (active). When G is high, outputs enter a high-impedance state functionally equivalent to open-collector behavior, but this is achieved via internal disable logic, not a dedicated output-enable pin. This differs from 3-state multiplexers like the 74LS257, which use separate OE pins.

What is the maximum operating frequency supported by SN74ALS158NG4?

SN74ALS158NG4 does not specify a maximum clock or data rate in its datasheet. Instead, its usable frequency is determined by propagation delay: with tPHL/tPLH ≤ 12 ns (max) and typical values of 5–9 ns, it supports reliable operation in synchronous systems up to approximately 25 MHz for simple gating, and up to 40 MHz in short-path, low-load configurations. System-level timing must account for setup/hold times of upstream/downstream devices, especially when used in pipelined control logic.

Can SN74ALS158NG4 be used with 3.3 V logic systems?

No, SN74ALS158NG4 is not compatible with 3.3 V logic systems. It requires a 4.5 V to 5.5 V supply and is specified only for TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V). Driving its inputs from 3.3 V CMOS outputs may result in marginal or unreliable high-level recognition, and powering it from 3.3 V will cause functional failure. For mixed-voltage systems, level-shifting buffers or 3.3 V–compatible multiplexers (e.g., SN74LVC157A) should be used instead of SN74ALS158NG4.

Is SN74ALS158NG4 RoHS compliant?

Yes, SN74ALS158NG4 is RoHS compliant. According to Texas Instruments' packaging documentation, the N-package (PDIP) variant carries NIPDAU (nickel-palladium-gold) lead finish and meets RoHS Directive 2011/65/EU requirements. It contains no lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), or polybrominated diphenyl ethers (PBDE), and is suitable for use in environmentally regulated commercial and industrial products.