Texas Instruments SN74F157AN

Overview

SN74F157AN from Texas Instruments is a quad 2-input data selector/multiplexer with common strobe (G) control, operating across 0°C to 70°C, supporting 5 V supply, 20 mA low-level output drive, and ≤11 ns propagation delay (tPLH/tPHL). It routes one of two 4-bit input sources to four true outputs and is used in digital logic routing within industrial control panels and legacy microprocessor bus interfaces.

For engineers reviewing the SN74F157AN datasheet, SN74F157AN pinout, SN74F157AN application, or SN74F157AN equivalent, key selection considerations include its TTL-compatible input thresholds (VIL = 0.8 V, VIH = 2 V), buffered I/O, PDIP-16 package compatibility, and guaranteed operation under 5 V ±10% supply with 50 pF load.

Technical Context

The SN74F157AN implements four independent 2:1 multiplexers sharing a single active-low strobe (G) input: when G is high, all Y outputs are forced low; when G is low, the A/B select line determines whether inputs A1–A4 or B1–B4 pass to outputs Y1–Y4. Each channel provides true (non-inverted) data routing without latching or memory function.

It belongs to the 74F (Fast TTL) family, delivering improved speed over standard 74LS while maintaining TTL voltage compatibility. Its electrical behavior is defined at VCC = 4.5–5.5 V, with guaranteed VOL ≤ 0.5 V at IOL = 20 mA and VOH ≥ 2.5 V at IOH = −1 mA - critical for interfacing with downstream TTL or CMOS loads.

Key Specifications

Pinout & Package

SN74F157AN is supplied in a 16-pin plastic dual in-line package (PDIP), 300-mil width, with standard DIP footprint and through-hole mounting. Pin 1 is located at the top-left corner with notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74F157AN, SN74LS157N trades speed for lower power and SN74HC157N offers voltage flexibility at the cost of TTL interface compatibility - neither is pin- or logic-drop-in without validation of timing and voltage margins.

Availability

SN74F157AN is available at Aetrix Electronics and suitable for industrial control panels, legacy microcontroller peripherals, and digital test instrumentation requiring stable component supply and long-term obsolescence management.

Supply support for SN74F157AN 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 solutions with broad industrial and automotive qualification.

The SN74F157AN belongs to TI's 74F Fast TTL logic family, designed specifically for high-speed digital systems requiring TTL compatibility, robust noise immunity, and predictable timing in commercial-temperature environments.

FAQ

What is the maximum clock frequency supported by SN74F157AN in a multiplexed data path?

The SN74F157AN does not operate on a clock signal - it is combinatorial logic with propagation delay specified up to 11 ns (tPLH/tPHL). In practice, it supports reliable data switching in systems with ≤20 MHz bus toggle rates, assuming proper setup/hold timing relative to control signals A/B and G. The SN74F157AN datasheet confirms no internal clock or latch, so maximum usable frequency depends entirely on external timing constraints.

Can SN74F157AN drive LEDs directly without current-limiting resistors?

No - the SN74F157AN can sink up to 20 mA per output (IOL = 20 mA), but driving an LED directly risks exceeding absolute maximum ratings if forward voltage and supply conditions vary. A series resistor is mandatory to limit current; for example, with VCC = 5 V and typical red LED VF = 1.8 V, a 180 Ω resistor sets current to ~17.8 mA. Always verify against SN74F157AN's VOL specification (≤0.5 V) to ensure logic-low integrity.

Is SN74F157AN RoHS compliant?

Yes - according to TI's Package Option Addendum, SN74F157AN (orderable part number SN74F157AN and SN74F157AN.A) carries RoHS "Yes" status, with lead finish NIPDAU and exemption from MSL reflow requirements due to its PDIP package type. Full compliance documentation is available in TI's official materials declaration reports.

Does SN74F157AN have internal pull-up or pull-down resistors on its inputs?

No - the SN74F157AN has no internal termination resistors. Inputs A/B, G, and all data lines (1A–4B) require externally defined logic states; floating inputs may cause erratic output behavior or increased ICC. For unused inputs, tie to VCC or GND via 1–10 kΩ resistors per TI's 74F design guidelines. This requirement is explicitly stated in the SN74F157AN functional description and recommended operating conditions.

How does the strobe (G) input interact with the A/B select line in SN74F157AN?

In the SN74F157AN, the strobe (G) input is prioritized over A/B: when G is high, all four Y outputs are forced low regardless of A/B state or data inputs. Only when G is low does the A/B signal determine whether A or B inputs appear at the outputs. This hierarchical control enables global output disable for bus isolation - a feature confirmed in the SN74F157AN function table and logic diagram.