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Texas Instruments SN74HCS238DR
- Part No.:
- SN74HCS238DR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74HCS238DR.pdf
- Description:
- 3-TO-8 LINE DECODER DEMULTIPLEXE
- Quantity:
- Payment:
- Shipping:
Inventory:3,331
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Product details
Overview
SN74HCS238DR from Texas Instruments is a 3-to-8 line decoder/demultiplexer with Schmitt-trigger inputs, designed for memory address decoding and data routing in industrial and automotive systems. It operates from 2 V to 6 V, delivers ±7.8-mA output drive at 6 V, supports –40°C to +125°C ambient temperature, and features three active-low strobe inputs (G₀, G₁) plus one standard strobe (G₂) for cascading and demux control.
For engineers reviewing the SN74HCS238DR datasheet, SN74HCS238DR pinout, SN74HCS238DR application, or SN74HCS238DR equivalent, key selection criteria include Schmitt-trigger noise immunity, low ICC (100 nA typical), 16-pin SOIC package compatibility, and precise 3-input address decoding with simultaneous output gating via three independent strobes.
Technical Context
The SN74HCS238DR 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 Schmitt-trigger inputs provide hysteresis (ΔVT = 0.6–1.6 V across supply range), enabling robust operation with slow-rising or noisy address/control signals without external conditioning.
Functional behavior is governed by a three-strobe enable architecture: outputs are forced low when any of G₂ (active-high), G₁ or G₀ (active-low) is asserted; otherwise, only one Y₀–Y₇ output goes high per A₂A₁A₀ binary input, while all others remain low - supporting both discrete device selection and time-multiplexed data routing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - enables direct interface with 3.3-V and 5-V logic families without level shifters |
| Output Drive Strength | ±7.8 mA at 6 V - sufficient to directly drive multiple CMOS inputs or small LED loads |
| Propagation Delay | 7 ns typical at 6 V - ensures timing-critical address decoding in sub-100-MHz systems |
| Input Hysteresis (ΔVT) | 0.6 V min at 6 V - rejects >600-mV peak-to-peak noise on address/strobe lines |
| Quiescent Supply Current | 100 nA typical - supports ultra-low-power battery-backed or always-on subsystems |
| Operating Temperature | –40°C to +125°C - qualified for under-hood automotive and industrial control environments |
| Input Leakage Current | ±100 nA max at 6 V - minimizes voltage droop on high-impedance bus lines |
Pinout & Package
SN74HCS238DR is supplied in a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard JEDEC MS-012AC footprint and gull-wing leads. Thermal performance includes RθJA = 122.2°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0, A1, A2 | Address select inputs | Binary-coded 3-bit input determining which of eight outputs (Y0–Y7) activates high |
| G0, G1 | Active-low strobe inputs | Asserting either forces all outputs low - used for chip-select gating or hierarchical decoding |
| G2 | Active-high strobe input | Enables decoder function only when high; complements G0/G1 for flexible enable logic |
| Y0–Y7 | Decoder outputs | Active-high, mutually exclusive outputs - only one high per valid address when strobes permit |
| VCC | Positive supply | Power rail for internal logic and output drivers; requires local 0.1-μF bypass capacitor |
| GND | Ground reference | Return path for all supply and signal currents; must be low-impedance for stable switching |
Key Features
| Feature | Design Value |
|---|---|
| Schmitt-trigger inputs | Provides 0.6–1.6 V hysteresis to reject noise and accept slow-rising signals without oscillation |
| Three independent strobes | Enables flexible cascading (e.g., two SN74HCS238DRs for 4-to-16 decode) and dynamic output blanking |
| Low ICC quiescent current | 100 nA typical allows integration into power-sensitive applications like sensor nodes or sleep-mode controllers |
| Wide VCC range | 2–6 V operation supports mixed-voltage system design and brown-out resilience down to 2 V |
| CMOS push-pull outputs | Balanced sourcing/sinking capability eliminates need for external pull-ups in most bus-driving scenarios |
Applications
| Memory Address Decoding | Shared Data Bus Control |
|---|---|
Use Scenario: Selecting one of eight SRAM or Flash devices connected to a common 8/16-bit data bus in an embedded controller. IC Role / Device Role / Timing Role: Decoder translates 3-bit address lines into individual chip-select (CS) signals, enabling single-device access per transaction. Use Value: Reduces GPIO count required for memory expansion from eight dedicated lines to three address + three strobes, simplifying PCB routing and firmware management. | Use Scenario: Routing UART, SPI, or I²C signals to one of eight peripheral modules (e.g., sensors, ADCs, DACs) in a modular industrial I/O system. IC Role / Device Role / Timing Role: Demultiplexer uses strobe-controlled gating to isolate communication paths, preventing bus contention during multi-peripheral operations. Use Value: Eliminates need for eight separate transceivers or analog switches - leverages low propagation delay (7 ns) for real-time peripheral switching without protocol violation. |
| Automotive Body Control | Industrial PLC I/O Expansion |
Use Scenario: Driving eight discrete load drivers (e.g., relays, LEDs, solenoids) from a microcontroller in a vehicle body control module operating at 125°C ambient. IC Role / Device Role / Timing Role: Logic-level translator and selector that accepts noisy, slow-switching signals from mechanical switches or LIN bus interfaces. Use Value: Schmitt-trigger inputs tolerate switch bounce and EMI without external RC filtering; ±7.8-mA drive directly interfaces with most gate drivers or optocouplers. | Use Scenario: Expanding digital output capability of a programmable logic controller (PLC) CPU board to control 8 valves, indicators, or actuators in factory automation. IC Role / Device Role / Timing Role: Address-decoded output expander that synchronizes with PLC scan cycle via strobe inputs tied to system clock enable. Use Value: Enables deterministic, glitch-free output activation using G₂/G₁/G₀ to coordinate with safety interlocks or watchdog timers - critical for SIL-2 compliant designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-to-8 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HC238D | Same pinout and logic function but lacks Schmitt-trigger inputs; higher input sensitivity to noise | Not suitable for noisy or slow-transition environments (e.g., mechanical switch interfaces) | Select SN74HCS238DR where input signal integrity cannot be guaranteed |
| CD74HCT238E | TTL-compatible input thresholds (2 V/0.8 V); identical output drive and package | Required when interfacing with legacy 5-V TTL logic without level shifters | Choose CD74HCT238E only when driving from non-CMOS sources with strict VIH/VIL requirements |
Compared with SN74HC238D and CD74HCT238E, the SN74HCS238DR uniquely combines Schmitt-trigger noise immunity with wide VCC range and ultra-low ICC - making it the optimal choice for ruggedized, low-power, mixed-signal industrial and automotive decoding where input signal quality is uncontrolled.
Availability
SN74HCS238DR is available at Aetrix Electronics and suitable for memory address decoding, shared data bus control, automotive body electronics, industrial PLC I/O expansion, and sensor multiplexing requiring stable component supply across extended temperature and voltage ranges.
Supply support for SN74HCS238DR 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and consumer markets.
The SN74HCS238DR belongs to TI's HCS logic family - engineered for high-noise environments and low-power operation in automotive and industrial control systems where signal integrity and thermal resilience are critical.
FAQ
What is the maximum capacitive load the SN74HCS238DR can drive while meeting datasheet timing specs?
The SN74HCS238DR is characterized for CL = 50 pF in switching specifications. Propagation delay (tpd = 7 ns typical at 6 V) and transition time (tt = 4 ns typical) are guaranteed only up to this load. Driving larger capacitances increases delay and may cause timing violations in high-speed systems; layout optimization or buffer insertion is recommended beyond 50 pF.
Does the SN74HCS238DR require external pull-up resistors on its outputs?
No - the SN74HCS238DR features CMOS push-pull outputs capable of sourcing and sinking up to ±7.8 mA at 6 V. External pull-ups are unnecessary unless driving open-drain buses or interfacing with legacy logic families requiring specific voltage thresholds not met by the native VOH/VOL.
Can unused inputs on the SN74HCS238DR be left floating?
No - all unused inputs (A0–A2, G0–G2) must be terminated to VCC or GND. Floating CMOS inputs cause increased ICC, potential oscillation, and ESD susceptibility. TI recommends 10-kΩ pull-up/down resistors for configurable inputs; direct connection is acceptable for permanently fixed states.
How does the SN74HCS238DR behave when multiple strobe inputs are simultaneously asserted?
When any strobe input (G₂ high, or G₁/G₀ low) is active, all outputs (Y0–Y7) are forced low regardless of A2–A0 state. Simultaneous assertion has no conflict - the output disable function is OR-combined across strobes, ensuring deterministic low-state behavior for fail-safe gating.
Is the SN74HCS238DR pin-compatible with older 74-series decoders like the 74LS238?
No - while functionally similar, the SN74HCS238DR uses a modern 16-pin SOIC footprint with different pin assignments (e.g., GND at Pin 8, VCC at Pin 16) and CMOS electrical characteristics. Direct replacement requires PCB redesign; consult TI's migration guide for compatible drop-in alternatives if retrofitting legacy designs.
SN74HCS238DR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 7.8mA, 7.8mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74HCS238DR FAQ
1.How can I place an order for SN74HCS238DR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HCS238DR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SN74HCS238DR reliable?
The price and inventory of SN74HCS238DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HCS238DR is usually 5 days.
3.What payment methods are accepted for SN74HCS238DR?
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SN74HCS238DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HCS238DR order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SN74HCS238DR?
For technical support, including SN74HCS238DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HCS238DR requirements.
6.How does Aetrix verify that SN74HCS238DR is sourced from the original manufacturer or authorized distributors?
All SN74HCS238DR products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74HCS238DR meets industry standards.
7.What is the process for return or replacement of SN74HCS238DR?
All SN74HCS238DR units undergo pre-shipment inspection (PSI). If there is an issue with SN74HCS238DR, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SN74HCS238DR part is unused and in its original packaging.
Return procedure for SN74HCS238DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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