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Texas Instruments CD74ACT138M
- Part No.:
- CD74ACT138M
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
CD74ACT138M.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:267
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Product details
Overview
CD74ACT138M from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in SOIC-16 package, operating at 4.5–5.5 V supply, with 3.1–10.9 ns propagation delay (tPLH/tPHL), ±24 mA output drive, and TTL-compatible inputs. It serves as a high-speed memory address decoder in industrial control backplanes and data-routing subsystems.
For engineers reviewing the CD74ACT138M datasheet, CD74ACT138M pinout, CD74ACT138M application, or CD74ACT138M equivalent, this page delivers verified functional modes, real-world timing behavior under load, enable-input cascading logic, and validated alternatives for memory decoding and demux use cases.
Technical Context
The CD74ACT138M implements positive-logic 3-to-8 decoding with three independent enable inputs: one active-high (G1) and two active-low (G2A, G2B), enabling hierarchical expansion without external inverters. Its CMOS ACT process ensures TTL-level input compatibility while delivering bipolar-F speed with reduced power.
Propagation delays are balanced across all eight outputs (Y0–Y7), and output drive supports fanout to 15 F-family devices. The device operates across –55°C to +125°C, with ESD robustness exceeding ±2000 V HBM per MIL-STD-883.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - Ensures stable operation with standard 5 V logic rails and tolerance for rail droop in dense PCB layouts. |
| Propagation Delay (tPLH/tPHL) | 3.1 ns (min) to 10.9 ns (max) at VCC = 5 V, CL = 50 pF - Enables sub-10 ns address decoding in high-speed memory systems. |
| Output Drive Current | ±24 mA - Sustains reliable signal integrity driving multiple TTL loads or transmission lines up to 75 Ω at 125°C. |
| Input Compatibility | TTL-voltage compatible (VIH = 2 V, VIL = 0.8 V) - Interfaces directly with legacy 74LS/74F logic without level-shifting. |
| ESD Rating | ±2000 V HBM - Meets MIL-STD-883 requirement, supporting handling in non-EPA environments during prototyping. |
| Operating Temperature | –55°C to +125°C - Qualified for extended-temperature industrial and aerospace avionics applications. |
| Quiescent Supply Current | 8 μA (typ) at 25°C - Minimizes standby power in always-on control modules with multiple decoders. |
Pinout & Package
CD74ACT138M uses a 16-pin SOIC (D) package measuring 9.9 mm × 6.0 mm body size, with gull-wing leads and standard JEDEC MO-001AC footprint. Thermal resistance RθJA is 106.6°C/W, requiring minimal copper pour for thermal management in continuous operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A, B, C | Binary select inputs | 3-bit address lines determining which of Y0–Y7 activates; decoded in positive logic (low = selected output). |
| G1 | Active-high enable | Primary chip-select; device enabled only when G1 = HIGH and both G2A = G2B = LOW. |
| G2A, G2B | Active-low enables | Secondary enables allowing cascaded 24- or 32-line decoding without external inverters. |
| Y0–Y7 | Active-low decoded outputs | One output goes LOW per valid input combination; all remain HIGH when disabled - ideal for NAND-based memory enable trees. |
| VCC, GND | Power and reference | Single 5 V supply; bypass capacitor (0.1 µF) required adjacent to VCC pin to suppress switching noise. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables direct 24-line decoding with no external gates and 32-line decoding with only one inverter - reduces board area and routing complexity. |
| Balanced propagation delays | Ensures deterministic timing across all eight outputs, critical for synchronous memory access where skew between chip-select signals must be minimized. |
| ±24 mA output drive | Supports fanout to 15 F-family devices or drives 50–75 Ω transmission lines - eliminates need for buffer stages in high-density backplane designs. |
| SCR-latchup-resistant CMOS process | Prevents destructive latch-up during transient overvoltage or hot-insertion events - essential for field-replaceable module interfaces. |
| TTL-compatible inputs | Accepts standard 74LS/74F logic thresholds without pull-ups or level shifters - simplifies integration into mixed-technology legacy systems. |
Applications
| Industrial PLC Backplane Decoding | Automotive Engine Control Unit (ECU) Memory Mapping |
|---|---|
Use Scenario: Address decoding for modular I/O expansion slots in programmable logic controllers, where multiple peripheral cards share a common 16-bit address bus. IC Role / Device Role / Timing Role: Primary address decoder selecting individual slot enables; operates in cascade with identical CD74ACT138M units to generate 24 discrete slot-select signals. Use Value: Eliminates need for discrete logic gates or CPLDs in slot-enable generation, reducing BOM count and improving timing predictability across temperature. |
Use Scenario: Mapping flash memory banks and peripheral registers in dual-core automotive ECUs, where fast, deterministic chip-select assertion is required for real-time firmware execution. IC Role / Device Role / Timing Role: High-speed memory decoder interfacing between microcontroller address bus and parallel NOR flash devices; used with G1 as CPU chip-select and G2A/G2B tied to upper address bits. Use Value: Sub-11 ns propagation delay ensures zero wait-state access to boot ROM and configuration EEPROM, meeting ASIL-B timing constraints. |
| Test Equipment Digital Pattern Generator | Avionics Data Acquisition Module |
Use Scenario: Selecting one of eight DAC channels in automated test equipment generating multi-channel analog stimulus waveforms. IC Role / Device Role / Timing Role: Demultiplexer routing a common digital control word to one of eight parallel-output DACs; G2A/G2B driven by sequencer strobes, G1 by pattern trigger. Use Value: ±24 mA drive capability allows direct connection to DAC reference pins without buffering, maintaining monotonicity and settling time specs. |
Use Scenario: Enabling discrete sensor interface ICs (e.g., ADCs, transducer conditioners) in radiation-tolerant flight data recorders operating across –55°C to +125°C. IC Role / Device Role / Timing Role: Radiation-hardened-compatible decoder asserting enables on analog front-end ICs based on ARINC 429 bus commands; leverages extended temperature rating and HBM ESD robustness. Use Value: Guaranteed operation at 125°C ambient and ±2000 V HBM withstand enables use in uncooled avionics bays without derating or shielding overhead. |
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 |
|---|---|---|---|
| SN74ACT138DR | Same ACT logic family, identical pinout and timing, but rated for –40°C to +85°C only; lower RθJA (126.2°C/W) due to TSSOP package. | Suitable for commercial-grade instrumentation where extended temperature is not required; less suitable for under-hood automotive or industrial enclosures. | Select SN74ACT138DR only if ambient temperature stays below 85°C and board space favors TSSOP over SOIC. |
| CD74HC138E | High-speed CMOS (HC) variant: slower max delay (21 ns), lower drive (±5.2 mA), wider VCC range (2–6 V), but no TTL input compatibility. | Applicable in battery-powered or mixed-voltage systems where 3.3 V operation is needed, but incompatible with legacy 5 V TTL sources without level translation. | Choose CD74HC138E only when supply voltage flexibility or ultra-low static current (< 2 μA) outweighs need for TTL compatibility and speed. |
Compared with SN74ACT138DR and CD74HC138E, CD74ACT138M uniquely combines military-grade temperature range (–55°C to +125°C), TTL input compatibility, and sub-11 ns propagation in a standard SOIC-16 package - making it the sole option for high-reliability 5 V memory decoding where environmental extremes and legacy interface coexist.
Availability
CD74ACT138M is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive ECU memory mapping, and avionics data acquisition modules requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74ACT138M 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 logic solutions, with over 50 years of innovation in high-reliability logic families.
The CD74ACT138M belongs to TI's Advanced CMOS Technology (ACT) logic series, designed specifically for high-speed memory decoding and data-routing systems demanding TTL compatibility, low power, and extended temperature operation.
FAQ
What is the maximum operating temperature for CD74ACT138M?
The CD74ACT138M is specified for continuous operation from –55°C to +125°C, making it suitable for under-hood automotive, industrial motor drives, and aerospace applications where ambient temperatures exceed commercial-grade limits. This rating is confirmed in Section 4.3 of the TI SCHS329C datasheet and applies to the SOIC (D) package variant.
Does CD74ACT138M support TTL-level inputs?
Yes, CD74ACT138M features TTL-voltage compatible inputs with VIH = 2.0 V (min) and VIL = 0.8 V (max) across its full temperature range, enabling direct interface with 74LS, 74F, and other legacy TTL logic families without level-shifting circuitry - a key differentiator from HC-series decoders.
Can CD74ACT138M be used in cascaded 24-line decoding without external inverters?
Yes, CD74ACT138M's three enable inputs (G1 active-high, G2A/G2B active-low) allow implementation of a 24-line decoder using three devices with no external inverters. This is explicitly documented in Figure 7-1 and Section 6.3 of the TI datasheet, leveraging G2A/G2B for hierarchical selection.
What is the typical propagation delay of CD74ACT138M at 5 V supply?
At VCC = 5 V, CL = 50 pF, and TA = 25°C, CD74ACT138M exhibits typical propagation delays of 3.1 ns (tPLH/tPHL) from address inputs (A/B/C) to outputs (Y0–Y7). The maximum delay is 10.9 ns across –55°C to +125°C, as specified in Table 4-6 of the SCHS329C datasheet.
Is CD74ACT138M pin-compatible with CD74HC138E?
No, CD74ACT138M and CD74HC138E are not pin-compatible replacements. While both use 16-pin packages (SOIC and PDIP respectively), their electrical behaviors differ significantly: CD74ACT138M requires 4.5–5.5 V supply and accepts TTL inputs, whereas CD74HC138E operates from 2–6 V and has CMOS input thresholds - necessitating redesign of biasing and supply networks.
CD74ACT138M Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
CD74ACT138M FAQ
1.How can I place an order for CD74ACT138M through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74ACT138M 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 CD74ACT138M reliable?
The price and inventory of CD74ACT138M are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74ACT138M is usually 5 days.
3.What payment methods are accepted for CD74ACT138M?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74ACT138M transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74ACT138M?
CD74ACT138M orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74ACT138M 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 CD74ACT138M?
For technical support, including CD74ACT138M datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74ACT138M requirements.
6.How does Aetrix verify that CD74ACT138M is sourced from the original manufacturer or authorized distributors?
All CD74ACT138M 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 CD74ACT138M meets industry standards.
7.What is the process for return or replacement of CD74ACT138M?
All CD74ACT138M units undergo pre-shipment inspection (PSI). If there is an issue with CD74ACT138M, 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 CD74ACT138M part is unused and in its original packaging.
Return procedure for CD74ACT138M:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
CD74ACT138M Tags
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