Texas Instruments SN74AHCT139PW

Overview

SN74AHCT139PW from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in TSSOP-16 package, operating at 4.5–5.5 V, with propagation delays as low as 1 ns (typical), TTL-compatible inputs, and ±8 mA output drive. It serves high-speed memory decoding and data-routing applications where minimal system delay is critical.

For engineers reviewing the SN74AHCT139PW datasheet, SN74AHCT139PW pinout, SN74AHCT139PW application, or SN74AHCT139PW equivalent, key selection considerations include its dual-decoder architecture with independent active-low enables, 16-pin TSSOP thermal performance (θ_JA = 108°C/W), and compatibility with fast-enable memory systems requiring sub-access-time decoding latency.

Technical Context

The SN74AHCT139PW implements two independent 2-to-4 decoders, each with separate active-low enable (1G/2G) and select inputs (A/B), supporting both decoding and demultiplexing modes. Its fully buffered TTL-compatible inputs draw ≤1 µA, while outputs drive ±8 mA under 5-V operation.

It features no internal interconnect between decoder sections - enabling isolated channel control - and uses standard positive-logic decoding with active-low outputs (Y0–Y3). Latch-up immunity exceeds 250 mA per JESD 17, and ESD protection meets JESD 22 (2000-V HBM, 200-V MM, 1000-V CDM).

Key Specifications

Pinout & Package

TSSOP-16 (PW) package: 4.4 mm × 5.0 mm body, 1.2 mm max height, 0.65 mm pitch, exposed pad not present, RoHS-compliant NiPdAu lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHCT139PW, SN74AHCT139PWR offers identical functionality in optimized packaging for SMT lines, while SN74AHCT139DR trades miniaturization for improved heat dissipation and ease of prototyping - both retain full logic compatibility and timing equivalence.

Availability

SN74AHCT139PW is available at Aetrix Electronics and suitable for industrial control systems, memory subsystems, and legacy logic upgrades requiring stable component supply and long-term sourcing continuity.

Supply support for SN74AHCT139PW 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 90 years of innovation in high-reliability components.

The SN74AHCT139PW belongs to TI's AHCT logic family - designed for high-speed, 5-V TTL-compatible applications demanding low propagation delay, robust noise immunity, and industrial temperature operation.

FAQ

What is the maximum clock frequency supported by SN74AHCT139PW?

The SN74AHCT139PW is not a clocked device - it is a combinational decoder with no internal clock. Its usable switching rate depends on input transition speed and load capacitance. With 15-pF load and 5-V supply, maximum reliable toggle rate exceeds 100 MHz, limited by 8.5 ns worst-case propagation delay and input rise/fall rate (≤20 ns/V).

Does SN74AHCT139PW support 3.3-V input logic levels?

No - SN74AHCT139PW requires TTL-compatible input thresholds: V_IL ≤ 0.8 V and V_IH ≥ 2.0 V. While 3.3-V CMOS outputs often exceed 2.0 V, margin is reduced. For guaranteed 3.3-V interface, use SN74LVC139A or level-shifting circuitry. SN74AHCT139PW itself operates only from 4.5–5.5 V.

Can SN74AHCT139PW outputs drive LEDs directly?

Yes - each output can sink or source up to 8 mA. Driving a standard 2-mA LED (with series resistor) is safe and common. For higher-current LEDs, add a transistor buffer. Note that outputs are active-low, so LED anode connects to V_CC, cathode to Yx pin.

Is SN74AHCT139PW pin-compatible with older 74LS139 devices?

Yes - SN74AHCT139PW is functionally and pin-compatible with 74LS139, including identical pinout, truth table, and active-low outputs. It improves upon LS logic with faster propagation (8.5 ns vs. ~25 ns), higher output drive (±8 mA vs. ±8 mA sink only), and superior ESD/latch-up robustness.

What is the thermal resistance (θ_JA) of SN74AHCT139PW and how does it affect layout?

SN74AHCT139PW has θ_JA = 108°C/W in still air. At 20 mA total output current and 5 V supply, power dissipation is ~10 mW - resulting in <1.1°C junction rise. Layout should include at least two 100-nF ceramic decoupling capacitors near V_CC/GND pins and avoid routing high-speed traces adjacent to the package to prevent coupling.