Texas Instruments SN74HCS138QPWRQ1

Overview

SN74HCS138QPWRQ1 from Texas Instruments is an automotive-qualified 3-to-8 line decoder/demultiplexer with Schmitt-trigger inputs, operating across 2 V to 6 V supply, delivering ±7.8-mA output drive at 6 V, and featuring typical ICC of 100 nA for ultra-low-power memory selection and bus routing in engine control units and ADAS domain controllers.

For engineers reviewing the SN74HCS138QPWRQ1 datasheet, SN74HCS138QPWRQ1 pinout, SN74HCS138QPWRQ1 application, or SN74HCS138QPWRQ1 equivalent, key selection criteria include AEC-Q100 Grade 1 qualification (–40°C to +125°C), hysteresis-enabled noise immunity, TSSOP-16 wettable flank compatibility, and strobe-gated output disable functionality.

Technical Context

The SN74HCS138QPWRQ1 implements a single 3:8 decoder with three address inputs (A2–A0) and three independent strobe inputs (G2, G1, G0), where any active strobe forces all eight outputs high. Its CMOS push-pull outputs provide balanced sourcing/sinking capability up to ±7.8 mA at 6 V, enabling direct interface with standard logic loads without external buffers.

Schmitt-trigger inputs deliver hysteresis (ΔVT = 0.6 V min at 6 V), allowing reliable operation with slow-rising signals (<100 ns transition time) and rejecting noise up to ±300 mV peak-to-peak. The device operates within AEC-Q100 Grade 1 ambient temperature range (–40°C to +125°C) and meets HBM ESD Level 2 (±4 kV) and CDM Level C6 (±1.5 kV).

Key Specifications

Pinout & Package

SN74HCS138QPWRQ1 is packaged in a 16-pin TSSOP (PW) with wettable flanks, body size 5.00 mm × 4.40 mm, optimized for automated optical inspection (AOI) and high-reliability solder joint formation in automotive PCB assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCS138PWR and MC74HC138ADR2G, the SN74HCS138QPWRQ1 uniquely delivers automotive-grade thermal robustness, integrated noise rejection, and wettable flank manufacturability - making it the sole choice for production-tier automotive decoding where reliability and process control are mandatory.

Availability

SN74HCS138QPWRQ1 is available at Aetrix Electronics and suitable for engine control units, ADAS camera modules, electric power steering systems, and infotainment display backlights requiring stable component supply across automotive production lifecycles.

Supply support for SN74HCS138QPWRQ1 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 automotive ICs, with over 50 years of innovation in high-reliability silicon solutions.

The SN74HCS138QPWRQ1 belongs to TI's HCS logic family - designed specifically for automotive signal routing and memory selection where low power, noise immunity, and AEC-Q100 compliance are non-negotiable.

FAQ

What is the maximum operating temperature for SN74HCS138QPWRQ1?

The SN74HCS138QPWRQ1 is AEC-Q100 Grade 1 qualified with a specified ambient operating temperature range of –40°C to +125°C. This rating is validated across production lots and applies to continuous operation in automotive under-hood and transmission control environments. The junction temperature limit remains 150°C per absolute maximum ratings, but thermal design must ensure TJ stays within specification under worst-case power dissipation and airflow conditions. SN74HCS138QPWRQ1 thermal resistance (RθJA) is 141.2°C/W in its TSSOP package.

Does SN74HCS138QPWRQ1 support 2.5-V logic systems?

Yes, SN74HCS138QPWRQ1 supports 2.5-V operation within its 2 V to 6 V supply range. At 2.5 V, the device maintains guaranteed hysteresis (ΔVT ≥ 0.2 V), propagation delay ≤ 53 ns, and output drive ≥ ±4 mA. Input thresholds scale proportionally: VT+ = 0.7–1.5 V and VT– = 0.3–1.0 V, ensuring clean logic transitions. SN74HCS138QPWRQ1 is commonly used in mixed-voltage domains where 2.5-V microcontrollers interface with 3.3-V or 5-V peripherals via level-shifted address buses.

How does the strobe logic work on SN74HCS138QPWRQ1?

SN74HCS138QPWRQ1 uses three independent strobe inputs: G2 (active-high), G1 (active-low), and G0 (active-low). When any strobe is asserted - i.e., G2 = HIGH, or G1 = LOW, or G0 = LOW - all eight outputs (Y0–Y7) are forced HIGH regardless of address inputs A2–A0. Only when G2 = LOW AND G1 = HIGH AND G0 = HIGH does the decoder respond to A2–A0, asserting exactly one low output. This enables hardware-level output disable for safety-critical fault handling in automotive systems. SN74HCS138QPWRQ1 function table confirms this behavior across all combinations.

Can SN74HCS138QPWRQ1 drive LEDs directly?

SN74HCS138QPWRQ1 can drive low-current LEDs directly in active-low configuration: connect LED anode to VCC and cathode to any Yx output. At 6 V supply, SN74HCS138QPWRQ1 sinks up to 7.8 mA while maintaining VOL ≤ 0.33 V - sufficient for indicator LEDs drawing ≤5 mA. For higher-current or multi-LED loads, external FETs or constant-current drivers are recommended. Always verify total output current does not exceed ±35 mA per pin or ±70 mA total through VCC/GND, as specified in SN74HCS138QPWRQ1 absolute maximum ratings.

Is SN74HCS138QPWRQ1 pin-compatible with legacy 74HC138 devices?

SN74HCS138QPWRQ1 is functionally and pin-compatible with standard 74HC138 and 74HCT138 devices in TSSOP-16 packages, sharing identical pin assignments for A0–A2, G0–G2, Y0–Y7, VCC, and GND. However, SN74HCS138QPWRQ1 adds Schmitt-trigger inputs and automotive qualification - meaning it replaces legacy parts without layout changes but provides superior noise immunity and temperature range. SN74HCS138QPWRQ1 retains the same 16-pin TSSOP footprint and mechanical dimensions (5.00 mm × 4.40 mm) as SN74HC138PWR.