Texas Instruments SN74HCT139D

Overview

SN74HCT139D from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in SOIC-16 package, operating at 4.5–5.5 V, with 10 ns typical propagation delay, ±4-mA output drive, and TTL-compatible inputs. It serves as a high-speed memory address decoder in industrial control systems and data-routing subsystems.

For engineers reviewing the SN74HCT139D datasheet, SN74HCT139D pinout, SN74HCT139D application, or SN74HCT139D equivalent, this page delivers verified functional modes, real-world timing behavior under 50-pF load, supply-current limits, and cascading enable logic implementation guidance.

Technical Context

The SN74HCT139D integrates two independent decoders, each with active-low enable (G) and two select inputs (A, B), driving four active-low outputs (Y0–Y3). Its fully buffered inputs present only one normalized LSTTL load, minimizing fanout burden on upstream drivers.

Propagation delay is specified at 12–51 ns across voltage and temperature, with switching tested under CL = 50 pF. The device supports cascading via shared or independent enable lines, enabling 4-to-16 line expansion without external logic.

Key Specifications

Pinout & Package

SN74HCT139D uses a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with 1.27-mm lead pitch and gull-wing terminations suitable for reflow assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT139D, SN74HC139DR trades guaranteed TTL input compatibility for broader voltage operation, while 74ACT139SCX sacrifices industrial temperature support and quiescent current efficiency for superior speed and output strength-making SN74HCT139D optimal for robust, 5-V industrial decoding where timing margin and legacy interoperability are critical.

Availability

SN74HCT139D is available at Aetrix Electronics and suitable for industrial control panels, programmable logic controllers, and embedded instrumentation requiring stable component supply and long-term lifecycle assurance.

Supply support for SN74HCT139D 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 industrial-grade qualification.

The SN74HCT139D belongs to TI's 74HCT logic family-designed specifically for high-speed memory decoding and data-routing systems requiring TTL-compatible inputs, low power, and deterministic propagation delay.

FAQ

What is the maximum propagation delay for SN74HCT139D under recommended operating conditions?

The maximum propagation delay (tpd) for SN74HCT139D is 51 ns at VCC = 4.5 V and TA = 25 °C, measured with CL = 50 pF. At 5.5 V, max tpd drops to 50 ns. These values apply to both A/B→Y and G→Y transitions and are validated across the full –40 °C to +85 °C operating range per TI's SCLS066E datasheet.

Can SN74HCT139D drive standard 74LS-series inputs directly?

Yes, SN74HCT139D can drive up to 10 LSTTL loads directly. Its ±4-mA output drive at 5 V meets the 74LS input current requirements (IIH ≤ 20 µA, IIL ≤ 0.4 mA), and its TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) ensure reliable interfacing with 74LS outputs without level shifters.

Is SN74HCT139D pin-compatible with other package variants like SN74HCT139N or SN74HCT139DBR?

Yes, SN74HCT139D is functionally and pinout-identical to SN74HCT139N (PDIP-16) and SN74HCT139DBR (SSOP-16): all share identical pin numbering, signal assignments, and electrical behavior. Only mechanical dimensions and thermal characteristics differ-SOIC (D) offers 73 °C/W RθJA versus 67 °C/W for PDIP (N) and 82 °C/W for SSOP (DB).

Does SN74HCT139D require external pull-up resistors on its outputs?

No, SN74HCT139D outputs are push-pull and do not require external pull-ups. All Y0–Y3 outputs actively drive high or low; they are not open-drain. Pull-ups would conflict with internal output drivers and risk excessive current-TI explicitly specifies direct connection to LSTTL or CMOS inputs without termination.

What is the recommended bypass capacitor for SN74HCT139D?

Texas Instruments recommends a 0.1-µF ceramic capacitor placed as close as possible to the VCC (pin 16) and GND (pin 8) terminals of SN74HCT139D. This minimizes high-frequency supply noise and stabilizes transient current demands during output switching-critical for maintaining tpd consistency and preventing ground bounce in dense logic layouts.