Texas Instruments SN74HC139D

Overview

SN74HC139D from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in SOIC-16 package, operating from 2 V to 6 V, with typical propagation delay of 10 ns at 5 V, ±4-mA output drive, and low 80-μA max ICC. It serves as a high-speed memory address decoder or data routing switch in embedded control and digital logic systems.

For engineers reviewing the SN74HC139D datasheet, SN74HC139D pinout, SN74HC139D application, or SN74HC139D equivalent, key selection criteria include active-low enable architecture, dual independent decoder channels, TTL-compatible output drive, and SOIC-16 thermal performance (RθJA = 73°C/W).

Technical Context

The SN74HC139D integrates two fully buffered 2-to-4 decoders sharing no internal signal paths-each has dedicated A/B select inputs and individual active-low G enable. Its CMOS design ensures one normalized load per input and rail-to-rail output swing under load.

Each decoder operates independently: when G is high, all four outputs (Y0–Y3) are forced high; when G is low, only the selected Yx is driven low (active-low outputs), while others remain high. Input transition times are specified down to 400 ns at 6 V, supporting clean switching in synchronous digital systems.

Key Specifications

Pinout & Package

SN74HC139D uses a 16-pin SOIC (D) package with nominal body size 9.90 mm × 3.90 mm and 1.27-mm lead pitch. Thermal resistance is RθJA = 73°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual 2-to-4 decoder applications.

Compared with SN74HC139D, SN74HCT139DR offers guaranteed TTL-level input compatibility at no layout change, while 74AC139PC delivers 38% lower propagation delay at the cost of 500× higher static current - making SN74HC139D optimal for balanced speed/power trade-offs in general-purpose digital systems.

Availability

SN74HC139D is available at Aetrix Electronics and suitable for industrial control panels, automotive body electronics, and consumer appliance logic subsystems requiring stable component supply across multi-year production cycles.

Supply support for SN74HC139D 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 founded in 1930, delivering analog, embedded processing, and logic solutions with emphasis on reliability, longevity, and broad documentation support.

SN74HC139D belongs to TI's HC (High-Speed CMOS) logic family, designed for pin-compatible upgrades from LS-TTL with lower power, wider voltage range, and improved noise immunity in industrial and commercial digital systems.

FAQ

What is the maximum clock frequency supported by SN74HC139D in demultiplexer mode?

SN74HC139D does not operate on a clock signal - it is combinational logic. Its usable toggle rate depends on propagation delay and system setup/hold timing. With 12 ns max tpd at 6 V, it reliably supports address/data bus switching up to ~40 MHz in well-designed layouts with controlled trace lengths and proper termination.

Can SN74HC139D drive LEDs directly without current-limiting resistors?

No. SN74HC139D outputs are rated for ±4 mA at 5 V, but sustained LED current typically exceeds this. Driving even a single standard 20-mA LED would exceed absolute maximum ratings and cause output degradation. Always use external series resistors - e.g., 330 Ω for ~12 mA at 5 V with VOH ≈ 4.4 V.

Is SN74HC139D pin-compatible with SN74LS139N?

Yes - SN74HC139D and SN74LS139N share identical pin assignments and functional block diagrams. However, SN74HC139D requires no pull-up resistors on outputs (due to active-pull capability), operates down to 2 V, and draws significantly less quiescent current than the bipolar LS version.

Does SN74HC139D support mixed-voltage operation (e.g., 3.3 V inputs with 5 V VCC)?

No. All inputs must remain within 0 V to VCC. Applying 3.3 V to an input while VCC = 5 V is acceptable (VIH = 3.15 V min at VCC = 4.5 V), but applying 5 V inputs to a 3.3 V-powered SN74HC139D violates absolute maximum ratings and risks damage. Use level translators for true mixed-voltage interfacing.

How should unused inputs on SN74HC139D be handled?

All unused inputs - including A, B, and G pins of either decoder - must be tied to a valid logic level (VCC or GND). Floating CMOS inputs cause increased ICC, erratic outputs, and potential latch-up. For example, tie unused G to VCC to disable that decoder, and tie unused A/B to GND to fix decode output state.