Texas Instruments SN74AHCT139NSRE4

Overview

SN74AHCT139NSRE4 from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin SOP (NS) package, operating at 4.5–5.5 V, with propagation delays as low as 1 ns (t_PLH/t_PHL at 15 pF), TTL-compatible inputs, and ±8 mA output drive. It serves high-speed memory decoding and data-routing functions in industrial control and embedded logic systems.

For engineers reviewing the SN74AHCT139NSRE4 datasheet, SN74AHCT139NSRE4 pinout, SN74AHCT139NSRE4 application, or SN74AHCT139NSRE4 equivalent, key selection criteria include its dual-decoder architecture with independent active-low enables, guaranteed 16-pin SOP (NS) footprint, 85°C industrial temperature rating, and compatibility with 5-V TTL-level signal chains requiring sub-10 ns timing margins.

Technical Context

The SN74AHCT139NSRE4 implements two independent 2-to-4 decoders, each with separate active-low enable (1G/2G) and binary select inputs (A/B), producing four active-low decoded outputs (Y0–Y3). Its fully buffered inputs present only one normalized load, minimizing fanout burden on upstream drivers.

It uses standard positive-logic decoding with active-low outputs and supports demultiplexing via the enable input acting as a data line. All logic thresholds are TTL-voltage compatible (V_IL ≤ 0.8 V, V_IH ≥ 2 V), ensuring interoperability with legacy 5-V TTL families without level translation.

Key Specifications

Pinout & Package

SOP (NS) package: 16-pin small-outline plastic, 5.3 mm × 10.2 mm body, 0.65 mm lead pitch, 1.75 mm max height, gull-wing leads, RoHS-compliant NiPdAu finish, MSL Level-1 (260°C reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT139DR and 74LV139PW, the SN74AHCT139NSRE4 delivers optimal balance of speed (7.2 ns typ), TTL compatibility (2 V V_IH), and industrial temperature support (–40°C to 85°C) in a cost-effective SOP-16 package-making it the preferred choice for legacy 5-V embedded systems where timing predictability and interface simplicity are critical.

Availability

SN74AHCT139NSRE4 is available at Aetrix Electronics and suitable for industrial control panels, programmable logic controllers, and embedded instrumentation requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for SN74AHCT139NSRE4 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 decades of experience delivering high-reliability components for industrial, automotive, and communications markets.

The SN74AHCT139NSRE4 belongs to TI's AHCT logic family-designed specifically for high-speed, 5-V TTL-compatible memory decoding and data routing in industrial and computing applications where timing precision and noise immunity are essential.

FAQ

What is the maximum clock frequency supported by SN74AHCT139NSRE4 in demultiplexer mode?

The SN74AHCT139NSRE4 does not operate on a clock signal-it is combinational logic. Its usable switching rate depends on propagation delay and load capacitance. With 15 pF load, t_PLH/t_PHL ≤ 8.5 ns supports reliable operation up to ~60 MHz toggle rate in demux applications, assuming clean signal edges and proper termination. The SN74AHCT139NSRE4 is not rated for continuous high-frequency toggling like a flip-flop; timing margins must be verified per application layout.

Can SN74AHCT139NSRE4 drive LEDs directly without current-limiting resistors?

No. While the SN74AHCT139NSRE4 provides ±8 mA output drive, its outputs are active-low open-collector equivalents (totem-pole, not true open-drain) and lack internal current limiting. Driving an LED directly risks exceeding absolute maximum output current (±25 mA) or damaging the output stage. Always use a series resistor-e.g., 330 Ω for a 5-V supply and red LED-to limit current to ≤8 mA. The SN74AHCT139NSRE4 is designed for logic interfacing, not power actuation.

Is SN74AHCT139NSRE4 pin-compatible with SN74LS139N?

Yes-SN74AHCT139NSRE4 shares identical pinout and logic function with SN74LS139N (16-pin PDIP), but differs in electrical characteristics: SN74AHCT139NSRE4 uses CMOS technology with TTL-compatible inputs, lower power, and faster speed, whereas SN74LS139N is bipolar LS-TTL. The SN74AHCT139NSRE4 can replace SN74LS139N in most 5-V systems, provided output loading and timing margins are re-verified due to its significantly shorter propagation delay (8.5 ns vs ~25 ns).

Does SN74AHCT139NSRE4 require external pull-up resistors on its Y outputs?

No. The SN74AHCT139NSRE4 features totem-pole outputs-not open-drain-so its Y0–Y3 outputs actively drive both high and low. Pull-up resistors are unnecessary and would degrade rise time and increase power consumption. Outputs switch between V_CC (VOH ≥ 3.8 V at –8 mA) and GND (VOL ≤ 0.44 V at 8 mA), meeting standard TTL logic levels without external components. The SN74AHCT139NSRE4 is designed for direct connection to other 5-V logic inputs.

What is the thermal resistance (θ_JA) of SN74AHCT139NSRE4 in its NS package?

The junction-to-ambient thermal resistance (θ_JA) for SN74AHCT139NSRE4 in the SOP (NS) package is 64°C/W, as specified in the TI datasheet SCLS267M. This value assumes standard JEDEC 2-layer board conditions (1-inch² copper pad, 2 oz Cu). For sustained operation near maximum ambient temperature (85°C), power dissipation should remain below 150 mW to keep junction temperature under 150°C. The SN74AHCT139NSRE4's typical ICC is 20 µA, so self-heating is negligible in static operation.