Texas Instruments SN74HCS238QDRQ1

Overview

SN74HCS238QDRQ1 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 AEC-Q100 Grade 1 systems (–40°C to +125°C). It features three active-low strobe inputs (G₀, G₁) and one standard strobe (G₂), ±7.8-mA output drive at 6 V, 100 nA typical supply current, and operates across 2 V to 6 V.

For engineers reviewing the SN74HCS238QDRQ1 datasheet, SN74HCS238QDRQ1 pinout, SN74HCS238QDRQ1 application, or SN74HCS238QDRQ1 equivalent, key selection criteria include automotive temperature compliance, Schmitt-trigger noise immunity for slow/noisy control signals, low-power operation in always-on domains, and compatibility with shared bus chip-select architectures.

Technical Context

The SN74HCS238QDRQ1 implements a high-speed silicon-gate CMOS 3:8 decoder with balanced push-pull outputs capable of sourcing and sinking up to ±7.8 mA at 6 V. Its three address inputs (A₀–A₂) select one of eight outputs (Y₀–Y₇), while three independent strobe inputs (G₂, G₁, G₀) gate all outputs to low when asserted - enabling cascading and demultiplexing functions.

Schmitt-trigger inputs provide hysteresis (ΔV_T = 0.6 V min at 6 V), allowing reliable operation with slow-rising/falling or noisy control signals without external conditioning. Input leakage remains ≤±100 nA at 6 V, and propagation delay is as low as 7 ns (typ) at 6 V with 50-pF load.

Key Specifications

Pinout & Package

SN74HCS238QDRQ1 is packaged in a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with gull-wing leads and standard JEDEC MS-012 outline. Pin 1 is marked by a beveled corner or dot; pin numbering follows counterclockwise convention from top-left when viewed from top with marking side up.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCS138QDRQ1 and MC74HC238ADTR2G, the SN74HCS238QDRQ1 uniquely combines AEC-Q100 Grade 1 qualification, Schmitt-trigger noise immunity, and ultra-low 100-nA supply current - making it the sole option for robust, low-power decoding in harsh automotive environments where signal integrity cannot be guaranteed.

Availability

SN74HCS238QDRQ1 is available at Aetrix Electronics and suitable for automotive body control modules, ADAS domain controllers, infotainment head units, and electric powertrain gateways requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for SN74HCS238QDRQ1 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 SN74HCS238QDRQ1 belongs to TI's HCS logic family, engineered specifically for automotive signal routing and decoding tasks where noise immunity, wide supply range, and AEC-Q100 compliance are mandatory design requirements.

FAQ

What is the maximum capacitive load the SN74HCS238QDRQ1 can drive while maintaining specified timing?

The SN74HCS238QDRQ1 is characterized for switching performance with a 50-pF load, and all timing specifications (e.g., t_pd = 7 ns typ at 6 V) are guaranteed under that condition. Driving larger capacitances increases propagation delay and transition time nonlinearly; for loads exceeding 50 pF, derating curves in Figure 6-1 and Figure 6-2 of the SN74HCS238QDRQ1 datasheet should be consulted to verify timing margins in the target application.

Does the SN74HCS238QDRQ1 require external pull-up or pull-down resistors on its address inputs?

No - the SN74HCS238QDRQ1 does not require external biasing on A₀, A₁, or A₂ because its Schmitt-trigger inputs tolerate undefined or floating states without excessive current draw or oscillation. However, TI strongly recommends tying unused address or strobe inputs to VCC or GND to prevent unintended decoding states; a 10-kΩ resistor is typical if dynamic control is needed later.

Can the SN74HCS238QDRQ1 outputs be paralleled to increase current drive capability?

Yes - two or more outputs of the SN74HCS238QDRQ1 (e.g., Y₀ and Y₁) may be wired in parallel to double the effective sink/source current, provided they are driven by identical address and strobe conditions. This technique is documented in Section 9.2.1.3 of the SN74HCS238QDRQ1 datasheet and maintains logic integrity as long as no conflicting states occur.

Is thermal pad connection required for the SN74HCS238QDRQ1 in SOIC (D) package?

No - the SN74HCS238QDRQ1 in the SOIC (D) package does not include a thermal pad. Thermal pad connectivity applies only to the WQFN (BQB) variant. For the D-package SN74HCS238QDRQ1, standard PCB copper pour under the body provides adequate thermal dissipation given its <2 µA typical power dissipation.

How does the SN74HCS238QDRQ1 behave when multiple strobe inputs are simultaneously asserted?

When any of G₂, G₁, or G₀ is asserted (G₂ = high, or G₁ = low, or G₀ = low), all eight outputs (Y₀–Y₇) are forced low regardless of address inputs - this is an OR logic function across strobes. The SN74HCS238QDRQ1 does not prioritize one strobe over another; simultaneous assertion has identical effect to single-strobe activation.