Texas Instruments SN74HCS238QPWRQ1

Overview

SN74HCS238QPWRQ1 from Texas Instruments is an automotive-qualified 3-to-8 line decoder/demultiplexer with Schmitt-trigger inputs, designed for memory address decoding and data routing in safety-critical vehicle systems. It operates from 2 V to 6 V, delivers ±7.8-mA output drive at 6 V, features typical ICC of 100 nA, and supports –40°C to +125°C ambient operation per AEC-Q100 Grade 1.

For engineers reviewing the SN74HCS238QPWRQ1 datasheet, SN74HCS238QPWRQ1 pinout, SN74HCS238QPWRQ1 application, or SN74HCS238QPWRQ1 equivalent, key selection criteria include Schmitt-trigger noise immunity, triple strobe control (G2, G1, G0), low-power CMOS push-pull outputs, and TSSOP-16 packaging qualified for automotive environments.

Technical Context

The SN74HCS238QPWRQ1 implements a single 3:8 decoder with three address inputs (A2–A0) and three independent strobe inputs (G2, active-high; G1 and G0, active-low). When any strobe is asserted, all eight outputs (Y0–Y7) are forced low-enabling cascading and demultiplexing functions without external logic.

Its Schmitt-trigger inputs provide hysteresis (ΔVT = 0.6 V min at 6 V), enabling reliable operation with slow-rising/falling or noisy signals. The balanced CMOS push-pull outputs support bidirectional current drive up to ±7.8 mA at 6 V while maintaining VOH ≥ 5.4 V and VOL ≤ 0.33 V under full load.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00 mm × 4.40 mm body size) with exposed thermal pad (not connected in PW variant); RoHS-compliant, lead-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCS238QPWRQ1, SN74HCS138QPWRQ1 offers identical pinout but lacks Schmitt-trigger noise rejection, while MC74HC238ADTR2G omits AEC-Q100 validation-making SN74HCS238QPWRQ1 the only option meeting full automotive reliability, noise tolerance, and temperature requirements in a single TSSOP-16 package.

Availability

SN74HCS238QPWRQ1 is available at Aetrix Electronics and suitable for automotive infotainment systems, ADAS domain controllers, and vehicle diagnostic gateways requiring stable component supply across extended production lifecycles.

Supply support for SN74HCS238QPWRQ1 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-grade logic solutions with decades of automotive qualification expertise.

The SN74HCS238QPWRQ1 belongs to TI's HCS logic family-designed specifically for low-power, noise-immune automotive signal routing and memory interface applications where reliability across extreme temperature and EMI conditions is mandatory.

FAQ

What is the maximum capacitive load the SN74HCS238QPWRQ1 can drive while meeting all datasheet timing specifications?

The SN74HCS238QPWRQ1 is characterized for CL = 50 pF in its switching characteristics table. While it can drive larger loads, propagation delay and transition time degrade beyond this value. For guaranteed tpd ≤ 16 ns and tt ≤ 7 ns at 6 V, keep total output capacitance-including trace, probe, and load-≤50 pF. Exceeding this requires empirical validation of setup/hold margins in the target system.

Does the SN74HCS238QPWRQ1 require external pull-up or pull-down resistors on unused address inputs?

Yes-unused address inputs (A0–A2) and strobe inputs (G0–G2) must be terminated to either VCC or GND to prevent floating states and undefined outputs. TI recommends 10-kΩ resistors for predictable default logic levels. Schmitt-trigger inputs tolerate slow transitions but do not eliminate the need for DC biasing; floating inputs risk increased ICC and metastability.

Can the SN74HCS238QPWRQ1 outputs be paralleled to increase drive strength?

Yes-two or more outputs of the SN74HCS238QPWRQ1 can be wired together to source or sink higher current, provided they are driven by identical logic states. This is explicitly supported in TI's Feature Description section. However, outputs must never be paralleled with opposing states (e.g., Y0 high and Y1 low), as that creates a short between VCC and GND and risks device damage.

What is the purpose of the thermal pad on the SN74HCS238QPWRQ1 TSSOP package?

The SN74HCS238QPWRQ1 in TSSOP (PW) package does not include a thermal pad-the thermal pad is exclusive to the WQFN (BQB) variant. The PW package relies on standard PCB copper pour and trace width for thermal dissipation. RθJA for PW is 141.2°C/W; adequate for typical automotive logic loads without additional heatsinking.

How does the SN74HCS238QPWRQ1 differ from the commercial-grade SN74HCS238PWR in terms of electrical performance?

Electrically, SN74HCS238QPWRQ1 and SN74HCS238PWR share identical DC and AC specifications-including VCC range, propagation delay, drive strength, and hysteresis. The Q1 suffix denotes automotive qualification: enhanced screening, AEC-Q100 Grade 1 temperature testing (–40°C to +125°C), HBM ESD Level 2 (±4 kV), and CDM Level C6 (±1.5 kV). No electrical parameter is relaxed or tightened in the Q1 version.