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Texas Instruments CD74ACT238E
- Part No.:
- CD74ACT238E
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
CD74ACT238E.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:195
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Product details
Overview
CD74ACT238E from Texas Instruments is a 3-line-to-8-line decoder/demultiplexer in PDIP-16 package, featuring TTL-compatible inputs, ±24-mA output drive, 3.9 ns typical propagation delay (tPLH/tPHL), and three enable inputs (G1, G2A, G2B) for cascading. It is designed for high-speed memory decoding and data-routing systems where low system delay and latch-up immunity are critical.
For engineers reviewing the CD74ACT238E datasheet, CD74ACT238E pinout, CD74ACT238E application, or CD74ACT238E equivalent, this device supports fast enable-based memory systems, 24-line/32-line decoder expansion without external inverters, and ESD-hardened operation in industrial temperature ranges (–55°C to 125°C).
Technical Context
The CD74ACT238E implements active-high and active-low enable logic (G1 high, G2A/G2B low) to select one of eight outputs (Y0–Y7) based on binary inputs A, B, C. Its balanced propagation delays (tPLH ≈ tPHL) and ±24-mA drive capability support direct interfacing with F-series TTL loads and transmission-line termination.
It uses SCR-latchup-resistant CMOS process with 2-kV HBM ESD protection and operates across VCC = 4.5 V to 5.5 V. Input transition rate limit (10 ns/V) and unit-load input structure (G2A/G2B = 1 unit load; A/B/C = 0.83) ensure stable timing behavior in mixed-signal environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures compatibility with standard 5-V TTL and ACT logic families. |
| Propagation Delay (tPLH/tPHL) | 3.9 ns min / 15.6 ns max (–55°C to 125°C) - Enables sub-16-ns worst-case decode latency in memory subsystems. |
| Output Drive | ±24 mA - Supports fanout to 15 F devices and direct 50-Ω transmission-line driving at 85°C. |
| Input Compatibility | TTL-voltage compatible (VIH = 2 V, VIL = 0.8 V) - Allows seamless interface with legacy TTL control logic without level shifters. |
| ESD Protection | ≥2 kV per MIL-STD-883, Method 3015 - Provides robust handling in manual assembly and industrial environments. |
| Operating Temperature | –55°C to 125°C - Qualified for aerospace, military, and extended-temperature industrial applications. |
| Quiescent ICC | 8 µA typical (25°C), 160 µA max (–55°C to 125°C) - Enables ultra-low static power in always-on decode paths. |
Pinout & Package
CD74ACT238E is housed in a 16-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width and through-hole mounting. Pin 1 is located at the top-left corner (notch-down orientation), and pin numbering follows standard counter-clockwise sequence.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (G2A) | Active-low enable input | Must be low with G2B low and G1 high for output enable; enables cascading without external inverters. |
| 2 (G2B) | Active-low enable input | Paired with G2A to form dual-active-low enable group; simplifies 24-line decoder expansion. |
| 3 (G1) | Active-high enable input | Primary global enable; high state required with both G2A/G2B low to activate decoding function. |
| 4 (C) | MSB select input | Binary address bit C (A2); determines higher-order output group (Y4–Y7 vs Y0–Y3). |
| 5 (B) | Mid select input | Binary address bit B (A1); used with A and C to fully decode 3-bit input into 8 outputs. |
| 6 (A) | LSB select input | Binary address bit A (A0); least-significant bit of 3-bit address bus for output selection. |
| 7 (Y0) | Active-low decoded output | Asserted low when A=B=C=0 and all enables active; drives memory chip-select or peripheral enable lines. |
| 8 (GND) | Ground reference | Power return path; must be low-impedance connection to minimize switching noise coupling. |
| 9 (Y1) | Active-low decoded output | Asserted low when A=1, B=C=0; used for second device selection in memory banks or I/O mapping. |
| 10 (Y2) | Active-low decoded output | Asserted low when B=1, A=C=0; supports modular address decoding in multi-bank SRAM/ROM systems. |
| 11 (Y3) | Active-low decoded output | Asserted low when A=B=1, C=0; enables compact 4-device decode trees without additional logic gates. |
| 12 (Y4) | Active-low decoded output | Asserted low when C=1, A=B=0; provides MSB-based partitioning for memory-mapped peripherals. |
| 13 (Y5) | Active-low decoded output | Asserted low when C=A=1, B=0; supports interleaved addressing schemes in high-density systems. |
| 14 (Y6) | Active-low decoded output | Asserted low when C=B=1, A=0; facilitates hierarchical decoding in FPGA-configurable logic blocks. |
| 15 (Y7) | Active-low decoded output | Asserted low when A=B=C=1; final output for full 3-bit decode; often tied to highest-priority interrupt controller. |
| 16 (VCC) | Positive supply | 5-V nominal supply; decoupling capacitor (0.1 µF ceramic) required within 1 cm of pin for stable high-speed operation. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables 24-line decoding without external inverters and 32-line decoding with only one inverter - reduces board area and signal count. |
| ±24-mA output drive | Directly drives 15 F-series TTL loads or 50-Ω transmission lines - eliminates need for buffer stages in memory-enable paths. |
| Balanced tPLH/tPHL propagation | Minimizes skew between rising/falling edge responses - critical for synchronous address decode in pipelined memory controllers. |
| SCR-latchup-resistant CMOS process | Guarantees no destructive latch-up under overvoltage or hot-insertion conditions - essential for ruggedized industrial backplanes. |
| TTL-compatible input thresholds | Accepts standard TTL logic levels (VIH ≥ 2 V, VIL ≤ 0.8 V) - interoperates with legacy 74LS/74F systems without level translation. |
Applications
| Memory Address Decoding | Data Demultiplexing |
|---|---|
|
Use Scenario: Selecting one of eight SRAM or ROM chips in a 64 KB memory bank using A15–A13 as select lines. IC Role / Device Role / Timing Role: High-speed address decoder that asserts chip-select (CS) signals with <16 ns worst-case delay, synchronized to memory enable timing. Use Value: Reduces effective memory access time by ensuring decode latency is less than typical 55 ns access time of fast ASRAMs. |
Use Scenario: Routing a single data bus to one of eight peripheral registers (e.g., UARTs, ADCs, GPIO expanders) in a microcontroller subsystem. IC Role / Device Role / Timing Role: Demultiplexer using G1 as data input and A/B/C as channel address - converts serial control stream into parallel register selects. Use Value: Eliminates need for dedicated demux ICs or FPGA logic resources, lowering BOM cost and routing complexity. |
| Industrial Control Backplane | Aerospace Avionics Subsystem |
|
Use Scenario: Enabling/disabling up to eight sensor signal conditioners or actuator drivers on a modular I/O carrier board operating at –40°C to 85°C. IC Role / Device Role / Timing Role: Cascaded enable controller using G2A/G2B for zone selection and G1 for per-module activation. Use Value: Achieves deterministic power sequencing and fault isolation via hardware-level gating - no firmware dependency. |
Use Scenario: Decoding command addresses in radiation-tolerant flight computer modules requiring extended temperature operation (–55°C to 125°C). IC Role / Device Role / Timing Role: Radiation-hardened-by-process (RHBP) decoder providing fail-safe address resolution for critical telemetry interfaces. Use Value: Meets MIL-STD-883 ESD requirements and operates reliably across full military temperature range without derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar decoder/demultiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ACT138N | Identical pinout, same 3-to-8 decode function, but features different enable polarity (G1 active-high, G2A/G2B active-low - matches CD74ACT238E). | Drop-in replacement in new designs; identical timing (tPLH = 3.9 ns), drive (±24 mA), and temperature range (–55°C to 125°C). | Select SN74ACT138N when sourcing from current TI production lines - identical functionality with updated packaging and traceability. |
| CD74HC238E | Same pinout and function but built on HC CMOS process: lower drive (±7.8 mA), slower speed (tPLH = 20 ns max), and narrower VCC range (2 V to 6 V). | Suitable only for low-power, non-critical timing applications; cannot replace CD74ACT238E in high-speed memory systems due to 2.5× longer propagation delay. | Choose CD74HC238E only if power budget is constrained and timing margin exceeds 20 ns - not recommended for memory decode or demux roles requiring <16 ns latency. |
Compared with CD74ACT238E, SN74ACT138N offers identical performance and drop-in compatibility, while CD74HC238E trades speed and drive strength for lower quiescent current - making it unsuitable for high-performance decode paths but viable for battery-powered control logic.
Availability
CD74ACT238E is available at Aetrix Electronics and suitable for high-reliability memory decoding, industrial I/O expansion, and aerospace avionics subsystems requiring stable component supply across extended temperature ranges and long lifecycle support.
Supply support for CD74ACT238E 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 U.S.-based semiconductor company specializing in analog, embedded processing, and logic solutions with over 90 years of innovation in industrial, automotive, and aerospace markets.
The CD74ACT238E belongs to TI's Advanced CMOS Technology (ACT) logic family, engineered for high-speed, low-power decoding in mission-critical memory and data-routing systems where timing precision and latch-up immunity are mandatory.
FAQ
What is the maximum operating temperature range for the CD74ACT238E?
The CD74ACT238E is rated for operation from –55°C to 125°C, meeting extended temperature requirements for aerospace, military, and harsh-environment industrial applications. This rating is verified per TI's production test flow and aligns with MIL-STD-883 thermal stress screening protocols. The CD74ACT238E maintains full electrical specifications across this range, including propagation delay and output drive capability.
Does the CD74ACT238E support TTL-level input signals directly?
Yes, the CD74ACT238E features TTL-voltage compatible inputs with VIH = 2 V (min) and VIL = 0.8 V (max), allowing direct connection to 74LS, 74F, and other standard TTL logic families without level-shifting circuitry. This compatibility is confirmed in the "Recommended Operating Conditions" table of the SCHS330 datasheet and applies across the full temperature range.
Can the CD74ACT238E be used as a demultiplexer, and how is that implemented?
Yes, the CD74ACT238E can function as a 1-to-8 demultiplexer by using G1 as the data input and A, B, C as the select lines. When G1 is driven with a logic signal and G2A/G2B are held low, the input appears inverted on the selected Yx output. This configuration is explicitly described in the "Application Information" section of the CD74ACT238E datasheet and requires no external components.
What is the output drive capability of the CD74ACT238E, and what does it mean for system design?
The CD74ACT238E delivers ±24 mA per output, enabling direct fanout to 15 F-series TTL devices or driving 50-Ω transmission lines at 85°C. This eliminates the need for buffer stages in memory chip-select paths and ensures reliable signal integrity in high-speed data-routing applications. The value is measured per TI's standard test conditions (IOH = –24 mA, IOL = 24 mA, VCC = 4.5 V).
Is the CD74ACT238E pin-compatible with other 3-to-8 decoders in TI's portfolio?
Yes, the CD74ACT238E shares identical pinout and function with SN74ACT138N, including matching enable polarity (G1 high, G2A/G2B low) and output behavior. Both devices use PDIP-16 packaging and meet the same AC/DC specifications. This allows direct substitution in existing layouts without PCB modification, provided the bill-of-materials reflects TI's current production status.
CD74ACT238E Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 24mA, 24mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
CD74ACT238E FAQ
1.How can I place an order for CD74ACT238E through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74ACT238E 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 CD74ACT238E reliable?
The price and inventory of CD74ACT238E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74ACT238E is usually 5 days.
3.What payment methods are accepted for CD74ACT238E?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74ACT238E transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74ACT238E?
CD74ACT238E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74ACT238E 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 CD74ACT238E?
For technical support, including CD74ACT238E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74ACT238E requirements.
6.How does Aetrix verify that CD74ACT238E is sourced from the original manufacturer or authorized distributors?
All CD74ACT238E 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 CD74ACT238E meets industry standards.
7.What is the process for return or replacement of CD74ACT238E?
All CD74ACT238E units undergo pre-shipment inspection (PSI). If there is an issue with CD74ACT238E, 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 CD74ACT238E part is unused and in its original packaging.
Return procedure for CD74ACT238E:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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