Texas Instruments SN74HC42ANSR

Overview

SN74HC42ANSR from Texas Instruments is a high-speed CMOS BCD-to-decimal decoder (1-of-10) with active-HIGH 4-bit BCD inputs and active-LOW mutually exclusive outputs. It operates at 2–6 V supply, delivers 14 ns typical propagation delay at 5 V, supports 1-of-8 demultiplexing via A3 control, and disables all outputs for invalid BCD codes (10–15), enabling reliable address decoding in digital logic systems.

For engineers reviewing the SN74HC42ANSR datasheet, SN74HC42ANSR pinout, SN74HC42ANSR application, or SN74HC42ANSR equivalent, key selection criteria include its active-LOW output architecture, TTL-compatible input thresholds (HCT variant), MSI-level integration, standard-output drive capability, and compatibility with legacy LSTTL systems requiring BCD-based selection or enable control.

Technical Context

The SN74HC42ANSR implements combinational logic that maps four binary-coded decimal inputs (A0–A3) to ten decoded outputs (Y0–Y9), where only one output is LOW per valid BCD input (0–9). Its internal design ensures all outputs go HIGH for input codes 10–15, preventing spurious activation in cascaded or memory-mapped systems.

It features a dedicated inhibit function via A3: when used as a 1-of-8 decoder, A3 acts as an enable/disable control; in demultiplexer mode, A3 serves as the data input while A0–A2 select one of eight outputs - leveraging the same silicon for dual functional roles without external logic.

Key Specifications

Pinout & Package

SN74HC42ANSR is supplied in a 16-pin plastic small-outline (SO-16) package with 1.27 mm pitch, conforming to JEDEC MS-012 and Philips SOT109 outlines. The package is surface-mount, RoHS-compliant, and rated for −40 °C to +85 °C operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar BCD-to-decimal decoding applications.

Compared with SN74HC42ANSR, SN74HCT42ANSR offers superior noise margin in TTL-driven systems, while 74HC42D provides identical functionality under a different brand and logistics chain - both require no schematic or layout changes but differ in supply-chain origin and interface compatibility scope.

Availability

SN74HC42ANSR is available at Aetrix Electronics and suitable for microcontroller I/O expansion, memory address decoding, industrial panel display control, and digital instrumentation multiplexing requiring stable component supply across extended production lifecycles.

Supply support for SN74HC42ANSR 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 specializing in analog, embedded processing, and logic solutions, with leadership in industrial, automotive, and communications markets.

The SN74HC42ANSR belongs to TI's 74HC high-speed CMOS logic family, designed for low-power, pin-compatible replacements of legacy TTL devices in digital control, interface, and address decoding applications.

FAQ

What is the operating voltage range for SN74HC42ANSR?

The SN74HC42ANSR operates over a supply voltage range of 2 V to 6 V. This wide range allows it to interface with both 3.3 V and 5 V logic systems, supporting mixed-voltage board designs and battery-powered applications where supply rails may vary. At 2 V, propagation delay increases to ~38 ns, while at 6 V it drops to ~11 ns - all within guaranteed specifications per the datasheet.

Does SN74HC42ANSR support demultiplexing functionality?

Yes, SN74HC42ANSR supports 1-of-8 demultiplexing by using A3 as the data input and A0–A2 as the select lines. In this mode, the device routes the A3 signal to one of eight outputs (Y0–Y7), with Y8 and Y9 unused. This dual-role capability is inherent to the logic design and requires no external components - making SN74HC42ANSR a cost-effective solution for signal routing in space-constrained designs.

How does SN74HC42ANSR handle invalid BCD inputs (10–15)?

SN74HC42ANSR forces all ten outputs (Y0–Y9) HIGH when any input code outside the valid BCD range (0–9) is applied. This behavior prevents unintended activation of downstream devices - critical in memory-mapped or peripheral-selection applications where spurious addressing could cause system errors. The logic ensures deterministic output states regardless of input combination.

Is SN74HC42ANSR pin-compatible with older TTL decoders?

SN74HC42ANSR is pin-compatible with low-power Schottky TTL (LSTTL) 74LS42 and meets JEDEC standard no. 7A. While electrical characteristics differ (e.g., CMOS input impedance, lower ICC), the 16-pin SO-16 footprint and signal mapping match exactly - enabling drop-in replacement in many legacy designs after verifying voltage level compatibility and load drive requirements.

What package type is used for SN74HC42ANSR?

SN74HC42ANSR uses a 16-pin plastic small-outline (SO-16) package, also known as SOP-16 or SOIC-16, with 1.27 mm lead pitch and body dimensions of 10.3 mm × 5.3 mm. It complies with JEDEC MS-012 and is RoHS-compliant, designed for surface-mount reflow assembly and rated for operation from −40 °C to +85 °C.