Texas Instruments SN74HC157DT

Overview

SN74HC157DT from Texas Instruments is a quadruple 2-line to 1-line data selector/multiplexer in SOIC-16 package, operating from 2V to 6V supply, delivering 11ns typical propagation delay at 5V, ±6mA output drive, and 80µA max ICC. It routes four independent 2:1 data paths under shared A/B address and active-low strobe (G) control, used in bus selection and signal routing within digital logic systems.

For engineers reviewing the SN74HC157DT datasheet, SN74HC157DT pinout, SN74HC157DT application, or SN74HC157DT equivalent, key selection criteria include its TTL-compatible CMOS inputs, low-power operation across industrial temperature range (–40°C to +85°C), synchronous channel enable via G input, and compatibility with LSTTL loads-critical for legacy interface bridging and compact logic consolidation.

Technical Context

The SN74HC157DT implements four independent 2:1 multiplexers sharing one address select (A/B) and one active-low strobe (G). When G is high, all Y outputs are forced low regardless of A/B or data inputs; when G is low, each Y output equals the selected input (A if A/B = L, B if A/B = H). All channels operate asynchronously with no internal clocking.

Its CMOS architecture provides high input impedance (≤1µA max II), rail-to-rail output swing (VOH ≥ 4.4V / VOL ≤ 0.26V at VCC = 4.5V), and robust noise immunity (VIH ≥ 3.15V, VIL ≤ 1.35V at 4.5V). Input transition time limits (≤500ns at 4.5V) ensure stable switching without oscillation.

Key Specifications

Pinout & Package

SN74HC157DT uses a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads compatible with automated SMT assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC157DT, SN74HC158DR offers inverted functionality useful in enable-driven architectures, while 74LVX157M delivers higher speed at 3.3V but sacrifices voltage range and direct 5V interoperability - making SN74HC157DT the optimal choice for industrial mixed-voltage signal routing where robustness and compatibility outweigh marginal speed gains.

Availability

SN74HC157DT is available at Aetrix Electronics and suitable for industrial control panels, legacy system upgrades, and digital test instrumentation requiring stable component supply and long-term obsolescence management.

Supply support for SN74HC157DT 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 specializing in analog, embedded processing, and logic solutions, with over 50 years of innovation in high-reliability digital ICs.

The SN74HC157DT belongs to TI's HC logic family, designed for low-power, high-noise-immunity digital signal routing in industrial, automotive, and communications infrastructure applications.

FAQ

What is the function of the G pin on the SN74HC157DT?

The G pin on the SN74HC157DT is an active-low strobe input that forces all four Y outputs low when driven high, regardless of the states of A/B or data inputs. This provides hardware-level output disable for bus isolation or fault-safe operation. When G is low, the device functions normally as a quadruple 2:1 multiplexer. The SN74HC157DT's G pin enables deterministic, glitch-free channel blanking synchronized across all four data paths.

Can the SN74HC157DT operate at 3.3V supply voltage?

Yes, the SN74HC157DT operates reliably at 3.3V supply voltage, meeting all recommended operating conditions: VIH ≥ 2.31V, VIL ≤ 0.99V, and tpd ≤ 19ns (typical ~15ns) with CL = 50pF. Its 2V–6V range makes it fully compatible with 3.3V systems, including mixed-voltage boards interfacing with 5V peripherals. The SN74HC157DT maintains full TTL-compatible input thresholds and ±6mA drive capability even at 3.3V.

Is the SN74HC157DT pin-compatible with other 74HC157 variants?

Yes, the SN74HC157DT shares identical pinout and function with all SOIC-16 variants of the 74HC157 family, including SN74HC157DR and SN74HC157DRG4. Pin assignments for A/B, G, VCC, GND, and all data I/Os match exactly across these D-package versions. The SN74HC157DT is electrically and mechanically interchangeable with those parts in SOIC-16 footprint designs, though its obsolete status requires verification of long-term supply chain viability.

What is the maximum capacitive load the SN74HC157DT can drive while maintaining specified timing?

The SN74HC157DT is characterized for CL = 50pF in its switching specifications, where tpd and tt values are guaranteed. While it can drive larger loads, performance degrades: at CL = 150pF, typical tpd increases to 33ns (at 6V). For designs requiring guaranteed 11ns timing, total load capacitance-including trace, probe, and input capacitance of downstream devices-must remain ≤50pF. The SN74HC157DT's 10pF input capacitance contributes to this budget and must be included in layout calculations.

Does the SN74HC157DT require external pull-up or pull-down resistors on unused inputs?

Yes, all unused inputs on the SN74HC157DT-including A/B, G, and any unconnected data inputs-must be terminated to either VCC or GND to prevent floating nodes, which cause excessive current draw, oscillation, or erratic output behavior. A 10kΩ resistor is recommended for pull-up/pull-down; direct connection is acceptable if the signal is permanently inactive. This requirement applies to every SN74HC157DT instance, as confirmed in TI's "Implications of Slow or Floating CMOS Inputs" application report.