Texas Instruments SN74S158N

Overview

SN74S158N from Texas Instruments is a quad 2-line-to-1-line data selector/multiplexer in a 16-pin PDIP package, operating over 0°C to 70°C, with typical propagation delay of 3.5 ns and output drive capability of ±20 mA. It performs logic-level signal routing in digital control systems, enabling selection between two input data sources per channel under common select and enable control.

For engineers reviewing the SN74S158N datasheet, SN74S158N pinout, SN74S158N application, or SN74S158N equivalent, key selection criteria include TTL-compatible input thresholds, guaranteed fan-out of 10 LS-TTL loads, single active-low enable architecture, and compatibility with legacy 74S-series timing and drive requirements in industrial control and test equipment design.

Technical Context

The SN74S158N implements four independent 2:1 multiplexers sharing a common strobe (G̅) input and dual select lines (S₀, S₁), where G̅ must be low for output enablement and S₀/S₁ determine which of the two input pairs (1A/1B through 4A/4B) drives each corresponding output (1Y through 4Y). All inputs are TTL-compatible with V_IL ≤ 0.8 V and V_IH ≥ 2.0 V at V_CC = 5 V.

Outputs exhibit complementary push-pull structure with guaranteed I_OH = –20 mA and I_OL = 20 mA at V_CC = 5 V, supporting direct interfacing to LS-TTL, standard TTL, and discrete logic loads without external pull-ups. The device uses bipolar Schottky-clamped transistor technology to achieve high-speed switching while maintaining noise immunity and stable DC characteristics.

Key Specifications

Pinout & Package

SN74S158N is housed in a 16-pin plastic dual in-line package (PDIP-N), 0.300-inch wide body, with 0.100-inch lead pitch and through-hole mounting. Package conforms to JEDEC MS-001 and TI's N package drawing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS158N, the SN74S158N delivers 4× faster propagation for time-critical routing, while SN74F158N further reduces delay by 29% and widens supply tolerance - making SN74S158N optimal for legacy S-TTL upgrades where timing headroom is limited but power constraints are secondary.

Availability

SN74S158N is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, digital test equipment signal routing, legacy computer bus arbitration, and embedded system debug interface multiplexing requiring stable component supply and long-term obsolescence management.

Supply support for SN74S158N 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 and embedded processing technologies with broad industrial, automotive, and communications product portfolios.

The SN74S158N belongs to TI's legacy 74S TTL logic family, designed specifically for high-speed digital control systems requiring robust noise immunity, precise timing, and direct compatibility with earlier-generation TTL infrastructure.

FAQ

What logic family does SN74S158N belong to, and how does it differ from LS or F series?

SN74S158N belongs to the 74S (Schottky TTL) logic family. It differs from 74LS by offering significantly faster propagation delay (3.5 ns vs. 14 ns) and higher output drive (±20 mA vs. ±8 mA), while consuming more quiescent current. Compared to 74F, SN74S158N has slightly slower speed (3.5 ns vs. 2.5 ns) and narrower V_CC tolerance (4.75–5.25 V vs. 4.5–5.5 V). SN74S158N remains electrically compatible with both families for level-shifting but requires careful power and thermal design due to its higher ICCQ.

Can SN74S158N directly replace SN74LS158N on an existing PCB?

Yes, SN74S158N is pin-compatible with SN74LS158N in the same PDIP-16 package and shares identical pinout, voltage levels, and logic function. However, SN74S158N draws higher supply current and generates more heat, so thermal validation and decoupling capacitor review are required. Also confirm that downstream loads can accept the faster edge rates and higher drive strength without signal integrity issues. SN74S158N retains full functional equivalence for quad 2:1 multiplexing.

What is the maximum clock/data rate supported by SN74S158N in multiplexer mode?

SN74S158N does not operate on a clock; it is combinatorial logic. Its maximum usable data rate depends on propagation delay (3.5 ns max) and system setup/hold timing. For clean signal routing with margin, it reliably supports data transitions up to approximately 100 MHz in well-designed PCB layouts with proper termination and decoupling. Critical timing paths should allow ≥5 ns minimum pulse width and observe 1 ns minimum input transition time per TI's recommended operating conditions.

Does SN74S158N support mixed-voltage operation, such as interfacing with 3.3 V logic?

No, SN74S158N is strictly a 5 V-only TTL device. Its input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V) and output swing (≈0.5 V low, ≈3.5 V high into 500 Ω) are specified only for V_CC = 5 V ±5%. It cannot reliably interface with 3.3 V CMOS or LVTTL without level-shifting circuitry. Driving SN74S158N inputs from 3.3 V logic may result in marginal high-level recognition; receiving its outputs into 3.3 V inputs risks overvoltage damage or latch-up unless current-limited or clamped.

Is SN74S158N still in active production, and what is its obsolescence status?

SN74S158N is listed as Active in TI's official packaging documentation with no announced discontinuance. TI continues to manufacture and support the part under its legacy logic portfolio, with documented PDIP-16 packaging, tube packaging (25 units), and RoHS-compliant NiPdAu lead finish. Long-term availability is managed via TI's Product Change Notification (PCN) process, and Aetrix Electronics maintains strategic inventory to support extended-life industrial programs requiring SN74S158N.