Texas Instruments CD74HC138QM96G4Q1

Overview

CD74HC138QM96G4Q1 from Texas Instruments is an automotive-qualified, high-speed CMOS 3-to-8-line inverting decoder/demultiplexer with three enable inputs (E1 active-high, E2 and E3 active-low), eight active-low outputs (Y0–Y7), 2-V to 6-V V_CC operation, and typical propagation delay of 13 ns at 5 V/15 pF. It serves as an I/O port or memory selector in automotive control modules requiring precise address decoding.

For engineers reviewing the CD74HC138QM96G4Q1 datasheet, CD74HC138QM96G4Q1 pinout, CD74HC138QM96G4Q1 application, or CD74HC138QM96G4Q1 equivalent, key selection criteria include automotive temperature range (−40°C to 125°C), inverting output logic, cascading capability via three enables, LSTTL load drive (10 loads), and SOIC-16 package compatibility with legacy HC138 designs.

Technical Context

This device implements a binary-decoded 3-input to 8-output logic function with fully complementary CMOS transistor pairs, delivering balanced rise/fall times and low dynamic power dissipation. Its enable architecture-two active-low (E2, E3) and one active-high (E1)-allows hierarchical cascading without external inversion logic.

Operation is strictly defined by the function table: all outputs remain high unless E1 = L, E2 = L, and E3 = H simultaneously, after which the selected Yx output goes low per A2:A0 state. Input thresholds meet 30% V_CC noise immunity requirements across the full automotive voltage and temperature range.

Key Specifications

Pinout & Package

CD74HC138QM96G4Q1 is housed in a 16-pin SOIC (D) package with standard 1.27 mm pitch and JEDEC MO-012AC outline. Thermal resistance θ_JA is 73°C/W, suitable for convection-cooled automotive PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC138QM96G4Q1, SN74HC138QPWRQ1 offers smaller footprint but reduced thermal performance, while CD74HCT138QM96Q1 provides guaranteed TTL input compatibility at slight speed cost-both require no PCB changes but differ in thermal and interface design trade-offs.

Availability

CD74HC138QM96G4Q1 is available at Aetrix Electronics and suitable for automotive engine control units, instrument clusters, and body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC138QM96G4Q1 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, specializing in analog, embedded processing, and automotive-grade silicon solutions with over 50 years of industry leadership.

CD74HC138QM96G4Q1 belongs to TI's automotive-qualified HC logic family, designed specifically for robust, low-power address decoding and signal routing in harsh-temperature vehicle subsystems.

FAQ

What is the operating temperature range certified for CD74HC138QM96G4Q1?

CD74HC138QM96G4Q1 is qualified for −40°C to +125°C operation per AEC-Q100 Grade 1 requirements. This rating is validated across all electrical parameters including propagation delay, output drive, and noise immunity-not just survival limits-making it suitable for under-hood engine control and transmission applications where ambient temperatures exceed 105°C.

Does CD74HC138QM96G4Q1 support cascading with other decoders, and how is it implemented?

Yes, CD74HC138QM96G4Q1 supports cascading using its three enable inputs: E1 (active-high), E2 (active-low), and E3 (active-low). To cascade two devices, tie E2 and E3 of the second decoder to one output (e.g., Y0) of the first, while connecting shared A0–A2 lines. This creates a 6-bit decode (32 outputs) with no additional logic, preserving timing integrity and minimizing board area.

What is the maximum capacitive load CD74HC138QM96G4Q1 can drive while maintaining specified propagation delay?

CD74HC138QM96G4Q1 maintains its 13 ns typical propagation delay at 5 V only up to 15 pF load capacitance. At 50 pF, t_pd increases to 30–45 ns depending on V_CC. For heavier loads, add a buffer stage or reduce trace length and stubs-TI recommends limiting total node capacitance to ≤25 pF for timing-critical automotive bus selects.

Can unused inputs on CD74HC138QM96G4Q1 be left floating in automotive applications?

No-unused inputs on CD74HC138QM96G4Q1 must be tied to V_CC or GND. Floating CMOS inputs cause increased ICC current, unpredictable output states, and potential latch-up in high-noise automotive environments. TI's application report SCBA004 mandates this for reliability; leaving any of A0–A2, E1, E2, or E3 unconnected violates AEC-Q100 stress testing requirements.

Is CD74HC138QM96G4Q1 pin-compatible with non-automotive versions like CD74HC138?

Yes, CD74HC138QM96G4Q1 uses the same SOIC-16 (D) package and identical pinout as CD74HC138, including A0–A2, E1–E3, Y0–Y7, V_CC, and GND. However, the Q1 version undergoes additional automotive qualification (AEC-Q100), has tighter AC/DC parameter screening across −40°C to 125°C, and features different marking (HC138Q) and reel packaging (2500 per reel).