Texas Instruments SN74HC138QDRQ1

Overview

SN74HC138QDRQ1 from Texas Instruments is an automotive-qualified 3-line-to-8-line decoder/demultiplexer in SOIC-16 package, operating from 2 V to 6 V, with typical propagation delay of 15 ns at 6 V, ±4-mA output drive at 5 V, and low ICC of 80 µA max - used for memory decoding and data routing in engine control units and ADAS domain controllers.

For engineers reviewing the SN74HC138QDRQ1 datasheet, SN74HC138QDRQ1 pinout, SN74HC138QDRQ1 application, or SN74HC138QDRQ1 equivalent, key selection criteria include automotive temperature range (−40°C to 125°C), three enable inputs (G1, G2A, G2B) for cascading, active-low outputs, and compatibility with LSTTL loads in safety-critical vehicle subsystems.

Technical Context

This device implements a binary-decoded 3-input logic array with three independent enable controls: one active-high (G1) and two active-low (G2A, G2B). All eight outputs (Y0–Y7) are active-low and mutually exclusive under valid enable conditions.

Propagation delay is specified per input-to-output path (A/B/C → Yx or enable → Yx), with tpd = 15 ns (typ) at VCC = 6 V and CL = 50 pF. Input transition times are constrained to ≤400 ns at 6 V to ensure timing compliance.

Key Specifications

Pinout & Package

SN74HC138QDRQ1 is housed in a 16-pin SOIC (D) package with 1.27 mm pitch, 10.3 mm × 6.5 mm body size, and 1.75 mm max height - compatible with standard automated SMT placement and reflow profiles (MSL Level-1).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-to-8 decoder applications.

Compared with SN74HC138QDRQ1, SN74HC238QDRQ1 offers functional equivalence with polarity inversion - critical for seamless integration with positive-logic peripherals - while MC74HC138ADR2G provides identical performance at lower qualification cost for non-automotive use cases.

Availability

SN74HC138QDRQ1 is available at Aetrix Electronics and suitable for engine control units, ADAS domain controllers, and body control modules requiring stable component supply across automotive production lifecycles.

Supply support for SN74HC138QDRQ1 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 company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for automotive, industrial, and personal electronics markets.

SN74HC138QDRQ1 belongs to TI's automotive HC logic family, designed specifically for high-speed, low-power decoding in safety-critical vehicle subsystems with stringent environmental and reliability requirements.

FAQ

What is the operating temperature range for SN74HC138QDRQ1?

The SN74HC138QDRQ1 is qualified for −40°C to 125°C operation per AEC-Q100 Grade 1, making it suitable for under-hood and powertrain applications where ambient temperatures exceed standard industrial limits. This range is validated across electrical parameters including propagation delay, output drive, and input thresholds - all guaranteed over the full span without derating.

Does SN74HC138QDRQ1 support 3.3 V logic systems?

Yes, SN74HC138QDRQ1 operates from 2 V to 6 V, with guaranteed performance at 3.3 V. At VCC = 3.3 V, VIH is 2.31 V (min), VIL is 1.09 V (max), and tpd is typically 19 ns - fully compatible with 3.3 V microcontrollers and FPGAs. No level-shifting circuitry is needed for interface with standard LVCMOS outputs.

How many enable inputs does SN74HC138QDRQ1 have, and what are their logic polarities?

SN74HC138QDRQ1 has three enable inputs: G1 (active-high), G2A (active-low), and G2B (active-low). All three must be simultaneously asserted - i.e., G1 = HIGH, G2A = LOW, G2B = LOW - for any output (Y0–Y7) to respond to address inputs A, B, C. This configuration simplifies cascading and eliminates external gating in multi-stage decode trees.

Can SN74HC138QDRQ1 be used as a demultiplexer?

Yes, SN74HC138QDRQ1 functions as a 1-to-8 demultiplexer when one enable input (e.g., G1) is used as the data input and A, B, C serve as select lines. With G2A and G2B held static (G2A = G2B = LOW), asserting G1 HIGH routes the logic state to the selected Yx output - enabling serial-to-parallel data distribution in diagnostic or configuration circuits.

What package type and RoHS status does SN74HC138QDRQ1 use?

SN74HC138QDRQ1 is supplied in a 16-pin SOIC (D) package with 1.27 mm pitch, RoHS-compliant lead finish (NIPDAU), and MSL Level-1 rating (unlimited floor life). The package drawing is TI's standard D package (JEDEC MS-012), with dimensions 10.3 mm × 6.5 mm × 1.75 mm, optimized for automated assembly and thermal performance in automotive PCB layouts.