Texas Instruments SN74HC139N

Overview

SN74HC139N from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in PDIP-16 package, operating from 2 V to 6 V with typical propagation delay of 10 ns at 5 V and ±4-mA output drive capability. It features two independent decoders, each with active-low enable (G) and fully buffered inputs, and is used in high-speed memory decoding and data-routing systems where low power (80-μA max ICC) and precise address selection are critical.

For engineers reviewing the SN74HC139N datasheet, SN74HC139N pinout, SN74HC139N application, or SN74HC139N equivalent, key selection considerations include its dual-decoder architecture with independent enables, TTL-compatible output drive, wide supply range, and suitability for cascaded address decoding in microcontroller-based peripherals and legacy memory interfaces.

Technical Context

The SN74HC139N implements two independent CMOS 2-to-4 line decoders, each accepting two binary address inputs (A, B) and one active-low enable (G). When G is high, all four outputs (Y0–Y3) are forced high; when G is low, exactly one output goes low based on the A/B combination, while others remain high - enabling precise channel selection in demultiplexing.

Its fully buffered inputs present only one normalized load to driving circuitry, and internal logic ensures no bus contention during transitions. The device supports cascading via enable chaining and operates reliably across −40°C to +85°C with input thresholds defined relative to VCC (VIH = 3.15 V min at VCC = 4.5 V, VIL = 1.35 V max).

Key Specifications

Pinout & Package

SN74HC139N uses a 16-pin Plastic Dual In-line Package (PDIP) with 19.31 mm × 6.35 mm body size and 2.54 mm lead pitch. Pin 1 is located at the left end of the top row (notch-side up), with leads arranged in two parallel rows of eight.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual decoder/demultiplexer applications.

Compared with SN74HC139N, SN74HCT139N offers improved input noise margin at 5 V but draws more quiescent current, while 74AC139PC delivers superior speed and drive strength at the cost of pinout incompatibility and higher power consumption.

Availability

SN74HC139N is available at Aetrix Electronics and suitable for industrial control panels, legacy system upgrades, and microcontroller peripheral expansion requiring stable component supply, long-term lifecycle support, and RoHS-compliant through-hole assembly.

Supply support for SN74HC139N 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 digital logic families.

The SN74HC139N belongs to TI's HC (High-Speed CMOS) logic series, designed for low-power, wide-supply-range applications in industrial, computing, and communications equipment where reliability and compatibility with legacy 5-V systems are essential.

FAQ

What is the maximum operating frequency supported by SN74HC139N?

The SN74HC139N does not specify a maximum clock frequency because it is a combinational logic device without internal clocking. Its usable switching rate is determined by propagation delay (12 ns max at 6 V) and system-level timing margins. For reliable operation in address decoding, input transitions should be spaced ≥50 ns apart to avoid metastability or race conditions. The SN74HC139N remains stable under continuous toggling within these constraints.

Can SN74HC139N operate at 3.3 V and interface directly with a 3.3-V microcontroller?

Yes, SN74HC139N supports 3.3 V operation (within its 2–6 V range) and has CMOS-compatible inputs that recognize 3.3-V logic levels as valid high/low signals. At 3.3 V, VOH is ≥3.17 V and VOL is ≤0.26 V (IOL = 4 mA), ensuring robust noise margins when driving other 3.3-V CMOS inputs. No level shifters are needed for bidirectional compatibility with 3.3-V GPIOs.

How are the two decoders in SN74HC139N isolated from each other?

The two decoders in SN74HC139N are fully independent: Channel 1 (pins 1–7) and Channel 2 (pins 9–15) share only VCC and GND. Their inputs (1G/1A/1B and 2G/2A/2B) and outputs (1Y0–1Y3 and 2Y0–2Y3) have separate signal paths with no internal coupling. This allows simultaneous, asynchronous operation - for example, enabling one decoder while holding the other disabled - without crosstalk or timing interaction.

Is SN74HC139N pin-compatible with older 74LS139 devices?

No, SN74HC139N is not pin-compatible with 74LS139. While both are dual 2-to-4 decoders in 16-pin DIP packages, their pin assignments differ: 74LS139 places VCC at pin 16 and GND at pin 8 (same as SN74HC139N), but assigns inputs/outputs to different pins (e.g., 74LS139 uses pins 1,2,3 for 1A,1B,1G vs. SN74HC139N's 1G,1A,1B order). Direct replacement requires PCB modification or adapter wiring.

What bypass capacitor value is recommended for SN74HC139N?

A 0.1-μF ceramic capacitor is recommended for SN74HC139N, placed as close as possible (≤5 mm) between pin 16 (VCC) and pin 8 (GND). This minimizes high-frequency supply noise and prevents output glitches during fast transitions. For systems with significant low-frequency ripple, paralleling a 1-μF tantalum or ceramic capacitor is acceptable - but the 0.1-μF part must remain the primary, locally mounted decoupler for the SN74HC139N.