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Texas Instruments CD74AC138EE4
- Part No.:
- CD74AC138EE4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
CD74AC138EE4.pdf
- Description:
- 3-LINE TO 8-LINE INVERTING DECOD
- Quantity:
- Payment:
- Shipping:
Inventory:4,461
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Product details
Overview
CD74AC138EE4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in 16-pin PDIP packaging, operating from 1.5 V to 5.5 V with ±24 mA output drive, balanced propagation delays, and SCR-latchup-resistant CMOS process. It features three enable inputs (G1, G2A, G2B) for cascading and is designed for high-speed memory decoding and data-routing systems.
For engineers reviewing the CD74AC138EE4 datasheet, CD74AC138EE4 pinout, CD74AC138EE4 application, or CD74AC138EE4 equivalent, key selection criteria include its wide supply voltage range (1.5–5.5 V), low propagation delay (as low as 2.8 ns at 5 V), 3-state outputs, ESD rating of ±2000 V HBM, and compatibility with legacy through-hole PCB layouts using the N-package.
Technical Context
The CD74AC138EE4 implements positive-logic decoding with active-low enables (G1, G2A, G2B) and three binary address inputs (A, B, C) to select one of eight active-low outputs (Y0–Y7). All outputs are actively driven - not open-drain - and enter high-impedance state when any enable is inactive.
Its architecture supports cascading via enable chaining: G2A/G2B can serve as outputs from upstream decoders, while G1 accepts external control. Propagation delays are balanced across input-to-output paths (tPLH ≈ tPHL), and switching characteristics are specified at 1.5 V, 3.3 V, and 5 V supply levels with 50 pF load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 1.5 V to 5.5 V - supports mixed-voltage system interfacing and battery-powered logic |
| Propagation Delay | 2.8 ns (max, 5 V, -40°C to 85°C) - enables sub-100 MHz address decoding in memory subsystems |
| Output Drive | ±24 mA - drives 15 F-type loads directly without buffering |
| ESD Rating | ±2000 V HBM - meets MIL-STD-883 requirement for robust handling in manufacturing |
| Operating Temp | -55°C to +125°C - qualified for industrial and extended-temperature applications |
| Power Dissipation Cap | 110 pF - defines dynamic power consumption at 5 V, 10 MHz operation |
| Input Thresholds | VIL = 0.3 V (at 1.5 V), VIH = 3.85 V (at 5.5 V) - ensures noise margin ≥30% of VCC across full range |
Pinout & Package
CD74AC138EE4 uses the 16-pin plastic dual in-line package (PDIP-N), body size 19.3 mm × 6.35 mm, with through-hole mounting and standard 0.3-inch row spacing. Pin 1 is marked by a notch or dot; thermal pad is not present (unlike WQFN variants).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A, B, C | Binary address inputs | Select one of eight outputs (Y0–Y7); logic states interpreted as CBA (MSB to LSB) |
| G1 | Enable input (active high) | Must be high AND both G2A and G2B low for decode function; enables cascading control |
| G2A, G2B | Strobe inputs (both active low) | Both must be low simultaneously with G1 high to activate outputs; used for hierarchical enable tree |
| Y0–Y7 | Active-low decoded outputs | Only one output low per valid input combination; all others remain high (not high-Z unless disabled) |
| VCC | Positive supply | Single rail powers all logic; bypass capacitor (0.1 µF) required near pin 16 |
| GND | Ground reference | Common return for all I/O and internal circuitry; connects to system ground plane |
Key Features
| Feature | Design Value |
|---|---|
| Wide-Voltage Operation | 1.5 V to 5.5 V supply range enables interoperability across 1.8 V, 3.3 V, and 5 V logic families without level shifters |
| Balanced Propagation Delays | tPLH and tPHL match within 0.2 ns (5 V) - critical for skew-sensitive address/data bus timing |
| Three Enable Inputs | G1 (high-enable), G2A/G2B (low-enable) allow flexible hierarchical decoding and daisy-chained demux trees |
| High Output Drive | ±24 mA per output supports direct fanout to 15 F-devices or termination into 50 Ω transmission lines |
| SCR-Latchup Immunity | CMOS process with guard rings prevents destructive latchup under transient overvoltage or ESD stress |
Applications
| Memory Address Decoding | Data Routing in Bus Systems |
|---|---|
Use Scenario: Selecting one of eight memory banks in a microcontroller-based embedded system with 24-bit address space. IC Role / Device Role / Timing Role: Address decoder that translates upper address bits (A15–A13) into chip-select signals for parallel SRAM/Flash devices. Use Value: Reduces address decoding latency to ≤2.8 ns, minimizing memory access cycle time and enabling >35 MHz bus operation. | Use Scenario: Distributing serial control data from a master MCU to eight peripheral ICs (e.g., ADCs, DACs, sensors) on a shared digital bus. IC Role / Device Role / Timing Role: Demultiplexer routing clock-synchronized command packets to individual slave devices based on 3-bit channel ID. Use Value: Eliminates need for discrete logic gates or FPGA resources; enables deterministic, glitch-free channel selection with <10 ns skew. |
| Cascaded Logic Expansion | Industrial Control I/O Selection |
Use Scenario: Building a 5-to-32 line decoder using two CD74AC138EE4 devices and one CD74AC139 to decode 5-bit inputs for PLC backplane addressing. IC Role / Device Role / Timing Role: First-stage decoder enabling second-stage devices via G2A/G2B outputs; G1 driven by MSB pair. Use Value: Maintains consistent propagation delay across stages (≤3.5 ns at 3.3 V), preserving setup/hold margins in real-time control loops. | Use Scenario: Selecting one of eight analog input channels for multiplexed signal conditioning in an industrial data acquisition module. IC Role / Device Role / Timing Role: Digital selector controlling analog switch enable lines (e.g., CD4067), synchronized with ADC sampling clock. Use Value: Provides TTL/CMOS-compatible control with ±24 mA drive - sufficient to directly drive multiple analog switch INH pins without buffer transistors. |
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 |
|---|---|---|---|
| SN74AC138N | Same AC logic family, identical pinout, same 16-pin PDIP package, but TI's commercial-grade version with -40°C to +85°C temp range | Suitable for commercial/industrial environments where extended temperature (-55°C to +125°C) is not required | Prefer SN74AC138N for cost-sensitive, non-military designs with standard ambient conditions |
| 74HC138N | Higher propagation delay (24 ns @ 4.5 V), lower drive (±4 mA), narrower VCC range (2–6 V), no SCR-latchup immunity | Limited to low-speed, low-noise applications; unsuitable for high-reliability or mixed-voltage systems | Choose only if legacy HC design reuse is mandatory and timing budget allows ≥20 ns delay |
Compared with SN74AC138N and 74HC138N, CD74AC138EE4 delivers superior temperature range, faster switching, higher drive strength, and enhanced latchup immunity - making it optimal for mission-critical industrial, aerospace, and test equipment where reliability and performance coexist.
Availability
CD74AC138EE4 is available at Aetrix Electronics and suitable for memory decoding, bus routing, industrial I/O selection, and cascaded logic expansion requiring stable component supply across extended temperature ranges.
Supply support for CD74AC138EE4 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 and embedded processing solutions, with decades of expertise in logic, timing, and interface ICs.
The CD74AC138EE4 belongs to TI's AC-series advanced CMOS logic family, engineered for high-speed, low-power memory and data-path applications demanding robust noise immunity and wide supply flexibility.
FAQ
What is the maximum operating frequency supported by CD74AC138EE4?
The CD74AC138EE4 does not specify a maximum clock frequency, as it is a combinational logic device. Its usable speed is determined by propagation delay: at 5 V, tPD ≤ 11 ns over temperature, supporting reliable operation in address/data paths up to ~35 MHz with appropriate setup/hold margins. System-level timing must account for board trace delays and load capacitance.
Does CD74AC138EE4 support 1.8 V logic interfaces?
Yes, CD74AC138EE4 operates down to 1.5 V, making it fully compatible with 1.8 V systems. At VCC = 1.8 V, VIH is 1.35 V (75% of VCC) and VIL is 0.45 V (25% of VCC), providing >400 mV noise margin. Input thresholds scale with supply, ensuring robust interfacing without external level shifters.
Can CD74AC138EE4 outputs drive LEDs directly?
No - CD74AC138EE4 outputs are active-push-pull (not open-drain) and rated for ±24 mA continuous current, but driving LEDs requires current-limiting resistors and careful thermal consideration. Direct LED connection risks exceeding absolute max ratings if forward voltage drops misalign; use external drivers or series resistors sized for 5–10 mA typical LED current.
Is CD74AC138EE4 pin-compatible with older CD74HC138 variants?
No - while both are 16-pin PDIP 3-to-8 decoders, CD74AC138EE4 and CD74HC138 share identical pinout but differ electrically: AC has faster speed, higher drive, wider VCC range, and different input thresholds. Swapping requires validation of timing, noise margins, and power supply compatibility; they are not drop-in replacements.
What is the purpose of the three enable inputs (G1, G2A, G2B) on CD74AC138EE4?
The three enables provide hierarchical control: G1 is active-high, G2A/G2B are active-low. All three must be asserted (G1=H, G2A=L, G2B=L) for decoding to occur. This allows flexible cascading - e.g., G2A/G2B can be driven by outputs of another decoder, while G1 serves as global enable - simplifying multi-level address decoding trees without external gates.
CD74AC138EE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AC
- 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:
- 1.5V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
CD74AC138EE4 FAQ
1.How can I place an order for CD74AC138EE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74AC138EE4 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 CD74AC138EE4 reliable?
The price and inventory of CD74AC138EE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74AC138EE4 is usually 5 days.
3.What payment methods are accepted for CD74AC138EE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74AC138EE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74AC138EE4?
CD74AC138EE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74AC138EE4 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 CD74AC138EE4?
For technical support, including CD74AC138EE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74AC138EE4 requirements.
6.How does Aetrix verify that CD74AC138EE4 is sourced from the original manufacturer or authorized distributors?
All CD74AC138EE4 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 CD74AC138EE4 meets industry standards.
7.What is the process for return or replacement of CD74AC138EE4?
All CD74AC138EE4 units undergo pre-shipment inspection (PSI). If there is an issue with CD74AC138EE4, 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 CD74AC138EE4 part is unused and in its original packaging.
Return procedure for CD74AC138EE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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