Texas Instruments SN74HCS157DR

Overview

SN74HCS157DR from Texas Instruments is a quadruple 2-to-1 CMOS multiplexer with Schmitt-trigger inputs, operating from 2 V to 6 V supply, delivering ±7.8-mA output drive at 6 V, and supporting industrial temperature range (–40°C to +125°C). It routes four parallel data channels using shared A/B select and active-low strobe (G) control, commonly used in bus switching and signal routing in embedded control systems.

For engineers reviewing the SN74HCS157DR datasheet, SN74HCS157DR pinout, SN74HCS157DR application, or SN74HCS157DR equivalent, key selection criteria include Schmitt-trigger noise immunity, low ICC (100 nA typical), 16-pin SOIC package compatibility, and guaranteed operation across wide voltage and temperature ranges.

Technical Context

The SN74HCS157DR implements four independent 2:1 multiplexers sharing one address-select (A/B) input and one active-low strobe (G) input. All outputs go low when G is high, enabling synchronous channel disable. Each channel selects between two inputs (xA/xB) based on A/B logic level, with asynchronous propagation.

Schmitt-trigger inputs provide hysteresis (ΔVT = 0.6 V min at 6 V), allowing robust operation with slow-rising signals and noise rejection up to ±0.3 V peak-to-peak. The device uses balanced CMOS push-pull outputs capable of sourcing/sinking up to 7.8 mA at 6 V while maintaining VOH ≥ 5.4 V and VOL ≤ 0.33 V under load.

Key Specifications

Pinout & Package

SN74HCS157DR is supplied in a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard 1.27-mm pitch and gull-wing leads. Pin 8 is GND; Pin 16 is VCC; all inputs are Schmitt-triggered; outputs are CMOS push-pull.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC157DR and 74LVC157APW, the SN74HCS157DR uniquely combines Schmitt-trigger noise immunity, ultra-low ICC, and 2–6 V flexibility-making it the only choice for robust, low-power, mixed-voltage multiplexing where signal integrity cannot be assumed.

Availability

SN74HCS157DR is available at Aetrix Electronics and suitable for industrial bus switching, automotive sensor multiplexing, embedded test point selection, and legacy system signal bridging requiring stable component supply across extended temperature and voltage ranges.

Supply support for SN74HCS157DR 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 designing analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74HCS157DR belongs to TI's HCS logic family, engineered for high-noise-immunity digital signal routing in harsh environments where reliability, low power, and wide supply tolerance are mandatory.

FAQ

What is the maximum operating frequency of the SN74HCS157DR?

The SN74HCS157DR supports a maximum switching frequency of 29 MHz at 6 V and –40°C to +125°C ambient temperature. This value is derived from the 16 ns maximum propagation delay (tpd) specified in the Electrical Characteristics table under recommended operating conditions. At lower supply voltages (e.g., 2 V), max frequency drops to 5 MHz due to increased tpd. The device does not require clock input-it operates asynchronously on data and control edges.

Does the SN74HCS157DR require external pull-up or pull-down resistors on unused inputs?

No, external resistors are not required-but unused inputs must be terminated to a defined logic level. The SN74HCS157DR's Schmitt-trigger inputs prevent floating states from causing excessive current or undefined behavior. TI recommends connecting unused inputs directly to VCC or GND. Pull-up/pull-down resistors (e.g., 10 kΩ) are optional only if dynamic control is needed later; direct connection is preferred for lowest power and noise immunity.

Can the SN74HCS157DR drive a 50-pF capacitive load while meeting all specifications?

Yes, the SN74HCS157DR is fully characterized for CL = 50 pF, as confirmed in the Switching Characteristics section. Propagation delay (tpd), transition time (tt), and max frequency values are all measured under this condition. Driving larger loads increases tpd and reduces noise margin but does not damage the device. For optimal timing compliance, keep trace capacitance ≤50 pF using short, narrow traces and avoid stubs.

What is the purpose of the strobe (G) pin on the SN74HCS157DR?

The strobe (G) pin on the SN74HCS157DR is an active-low enable that forces all four Y outputs LOW regardless of A/B select state or input data. When G = HIGH, outputs are unconditionally low-providing synchronized channel blanking. When G = LOW, normal multiplexing resumes. This feature simplifies system-level control, enabling safe bus isolation during reset or fault conditions without altering A/B logic.

Is the SN74HCS157DR RoHS-compliant and lead-free?

Yes, the SN74HCS157DR is RoHS-compliant and lead-free. Per TI's Packaging Information addendum, the part carries "Yes" for RoHS and uses NIPDAU (nickel-palladium-gold) or SN (tin) lead finish. It is rated MSL Level-1 with unlimited floor life and peak reflow tolerance up to 260°C, making it compatible with standard lead-free PCB assembly processes.