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Texas Instruments CD74ACT138PWR
- Part No.:
- CD74ACT138PWR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
CD74ACT138PWR.pdf
- Description:
- 3-Line to 8-Line Inverting Decod
- Quantity:
- Payment:
- Shipping:
Inventory:2,990
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Product details
Overview
CD74ACT138PWR from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in 16-pin TSSOP (PW) package, operating at 4.5–5.5 V with propagation delays as low as 2.6 ns (G2A/G2B → Y), ±24 mA output drive, and TTL-compatible inputs. It serves as a high-speed memory address decoder or data routing switch in industrial control and embedded logic systems.
For engineers reviewing the CD74ACT138PWR datasheet, CD74ACT138PWR pinout, CD74ACT138PWR application, or CD74ACT138PWR equivalent, key selection criteria include its triple-enable architecture (G1, G2A, G2B), balanced tPLH/tPHL timing, SCR-latchup-resistant CMOS process, and −55°C to +125°C operating range for ruggedized digital subsystems.
Technical Context
The CD74ACT138PWR implements positive-logic decoding with three binary select inputs (A, B, C) and three enable terminals (G1 active-high; G2A, G2B active-low), enabling cascaded 24- or 32-line decoding without external inverters. Its function table defines eight mutually exclusive active-low outputs (Y0–Y7), each asserted only when all enables are satisfied and the corresponding 3-bit address matches.
Internally, it uses advanced CMOS technology with bipolar-equivalent speed and reduced power consumption versus legacy F/AS/S families. Propagation delays are tightly balanced across input-to-output paths (tPLH ≈ tPHL), and output drive capability supports fanout to 15 F-type loads while maintaining VOL ≤ 0.44 V at 24 mA sink current under −40°C to +85°C conditions.
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 CMOS logic rails |
| Propagation Delay (G2A→Y) | 2.6 ns min / 10.5 ns max - enables sub-100 MHz address decoding in memory subsystems |
| Output Drive (IOL/IOH) | ±24 mA - supports direct interfacing to multiple F-family inputs or moderate capacitive loads |
| Input Compatibility | TTL-voltage level - accepts 0.8 V VIH and 2.0 V VIL thresholds without level-shifting |
| Operating Temperature | −55°C to +125°C - qualified for extended industrial and automotive under-hood applications |
| ESD Rating (HBM) | ±2000 V - exceeds MIL-STD-883 requirement, reducing board-level ESD protection overhead |
| Power Dissipation Cap | 110 pF typical Cpd - enables accurate dynamic power estimation in high-frequency switching |
Pinout & Package
CD74ACT138PWR is housed in a 16-pin TSSOP (PW) package measuring 5.00 mm × 6.4 mm body size, with 0.65 mm lead pitch and 1.2 mm maximum height. The exposed pad is not present - thermal management relies on PCB copper area under leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A (1) | Binary address input A | LSB of 3-bit decode address; must be terminated to VCC or GND if unused |
| B (2) | Binary address input B | Middle bit of address; contributes to Y0–Y7 selection per function table |
| C (3) | Binary address input C | MSB of address; determines upper/lower half of output group |
| G2A (4) | Active-low strobe enable | First enable leg; low enables decoding only when G2B = low and G1 = high |
| G2B (5) | Active-low strobe enable | Second enable leg; used with G2A to reduce external gating in cascaded designs |
| G1 (6) | Active-high strobe enable | Primary enable; high required for any output assertion - simplifies hierarchical enable trees |
| Y7 (7) | Active-low decoded output | Asserted only when A=B=C=1 and all enables active; drives bus or memory chip-select |
| GND (8) | Ground reference | Return path for all internal logic and output currents; requires low-inductance PCB connection |
| Y6 (9) | Active-low decoded output | Corresponds to address 110₂; used for peripheral selection or I/O mapping |
| Y5 (10) | Active-low decoded output | Corresponds to address 101₂; supports modular address space partitioning |
| Y4 (11) | Active-low decoded output | Corresponds to address 100₂; commonly assigned to high-priority system resources |
| Y3 (12) | Active-low decoded output | Corresponds to address 011₂; enables compact 3-to-8 expansion without glue logic |
| Y2 (13) | Active-low decoded output | Corresponds to address 010₂; used in demultiplexing data streams to parallel peripherals |
| Y1 (14) | Active-low decoded output | Corresponds to address 001₂; supports interrupt vector routing or status flag distribution |
| Y0 (15) | Active-low decoded output | Corresponds to address 000₂; typically assigned to boot ROM or primary controller interface |
| VCC (16) | Positive supply rail | Must be bypassed with 0.1 μF ceramic capacitor near pin; supports 5-V system integration |
Key Features
| Feature | Design Value |
|---|---|
| Triple Enable Architecture | G1 (active-high) + G2A/G2B (active-low) allows hierarchical decoding trees with zero external inverters for 24-line expansion |
| SCR-Latchup Resistant Process | CMOS fabrication prevents destructive latchup under transient overvoltage or ESD stress in noisy industrial environments |
| Balanced Propagation Delays | tPLH and tPHL match within 0.2 ns across all input/output combinations - critical for skew-sensitive address buses |
| TTL-Compatible Inputs | Accepts standard 5-V TTL logic levels directly, eliminating level translators in mixed-technology systems |
| High Output Drive (±24 mA) | Drives 15 F-family loads or 50-Ω transmission lines - suitable for backplane or long-trace routing |
Applications
| Memory Address Decoding | Peripheral Select Logic |
|---|---|
Use Scenario: Decoding 3-bit address bus to select one of eight SRAM, EPROM, or FPGA configuration blocks in a microcontroller-based system. IC Role / Device Role / Timing Role: Address decoder providing chip-select signals with <11 ns worst-case delay, minimizing memory access latency. Use Value: Enables single-cycle memory access at up to 90 MHz system clock by keeping decode overhead below 10% of cycle time. | Use Scenario: Routing UART, SPI, or GPIO control signals to eight distinct sensors or actuators in an industrial PLC rack. IC Role / Device Role / Timing Role: Demultiplexer converting serial command bits into parallel peripheral enable lines. Use Value: Reduces MCU GPIO count by 5 pins versus discrete AND gates while maintaining deterministic 3.1 ns output assertion timing. |
| Cascaded System Expansion | Interrupt Vector Mapping |
Use Scenario: Building a 32-line decoder using two CD74ACT138PWR devices and one inverter to manage 32 memory-mapped I/O registers. IC Role / Device Role / Timing Role: Primary and secondary decoder in hierarchical enable chain, where G1 of second device is driven by Y7 of first. Use Value: Achieves full 32-line decoding with only one external inverter - cuts BOM cost and layout area by 40% vs. alternative solutions. | Use Scenario: Assigning priority-encoded interrupt requests from eight peripheral sources to a fixed-vector interrupt controller. IC Role / Device Role / Timing Role: Priority encoder front-end generating unique active-low vector lines (Y0–Y7) synchronized to CPU interrupt acknowledge cycle. Use Value: Guarantees interrupt response latency ≤ 12 ns from request to vector assertion, meeting hard real-time deadlines in motor control firmware. |
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 |
|---|---|---|---|
| SN74ACT138PWR | Identical pinout, timing, and DC specs; same TI ACT family, but SN prefix denotes commercial-grade (-40°C to +85°C) temperature range | Limited to commercial ambient; unsuitable for extended temperature deployments requiring −55°C or +125°C operation | Select SN74ACT138PWR only for cost-sensitive consumer or office equipment where full industrial temp range is unnecessary |
| 74LCX138MTCX | Lower VCC range (2.0–3.6 V), 3.3-V logic compatible; 5.5 ns max tPD at 3.3 V; no TTL input compatibility | Designed for low-voltage portable or battery-powered systems; incompatible with 5-V buses without level translation | Choose 74LCX138MTCX when migrating to 3.3-V core logic and board-level voltage scaling is already implemented |
Compared with SN74ACT138PWR and 74LCX138MTCX, CD74ACT138PWR uniquely delivers full industrial temperature support, TTL input compatibility, and 5-V operation in the same TSSOP-16 footprint - making it the sole option for legacy 5-V systems requiring extended reliability.
Availability
CD74ACT138PWR is available at Aetrix Electronics and suitable for industrial control panels, test equipment, and avionics subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74ACT138PWR 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 ICs, with decades of heritage in high-reliability logic families including ACT, LVC, and AHC series.
The CD74ACT138PWR belongs to TI's advanced CMOS logic product line, engineered specifically for high-speed memory decoding and data-routing applications demanding low propagation delay, robust noise immunity, and extended temperature operation.
FAQ
What is the maximum operating frequency supported by the CD74ACT138PWR in a memory decoding application?
The CD74ACT138PWR does not specify a maximum clock frequency, but its worst-case propagation delay is 10.9 ns (−40°C to +85°C). When used in address decoding, this supports reliable operation in systems with memory access cycles ≥ 11 ns - effectively enabling up to ~90 MHz bus timing. Actual system frequency depends on board trace length, load capacitance, and enable signal timing margins. The CD74ACT138PWR remains functional well beyond this point, though setup/hold timing must be verified per application.
Does the CD74ACT138PWR require external pull-up or pull-down resistors on unused inputs?
Yes - all unused inputs (A, B, C, G1, G2A, G2B) of the CD74ACT138PWR must be externally tied to either VCC or GND to prevent floating states that cause excessive ICC current, logic instability, or increased EMI. TI explicitly mandates this in Section 4.3 of the datasheet. Leaving inputs unconnected risks undefined outputs and potential device malfunction. The CD74ACT138PWR has no internal termination; external biasing is mandatory for robust operation.
Can the CD74ACT138PWR be used as a demultiplexer, and how is data routed?
Yes - the CD74ACT138PWR functions as a 1-to-8 demultiplexer when one enable input (e.g., G2A) is used as the data input while A, B, C serve as select lines. With G2B held low and G1 high, asserting G2A high routes the logic state to the selected Y output (active-low). For example, A=B=C=0 and G2A=high yields Y0=low; all other Y outputs remain high. This mode is documented in TI's Application Information section and leverages the device's inherent enable-controlled output behavior. The CD74ACT138PWR supports true demux operation without modification.
What is the thermal resistance (RθJA) of the CD74ACT138PWR in its TSSOP package?
The junction-to-ambient thermal resistance (RθJA) for the CD74ACT138PWR in the PW (TSSOP-16) package is 126.2°C/W, as specified in Section 4.4 of the datasheet. This value assumes standard JEDEC high-K board conditions (2S2P). Actual thermal performance depends on PCB copper area, airflow, and nearby heat sources. No thermal pad is present in the TSSOP package, so heat dissipation occurs solely through leads and package body. For high-duty-cycle applications, derating per TI's thermal guidelines is recommended. The CD74ACT138PWR's low ICC (≤160 μA) minimizes self-heating under static conditions.
Is the CD74ACT138PWR pin-compatible with older 74LS138 or 74HC138 devices?
No - while the CD74ACT138PWR shares identical pin numbering and basic function with 74LS138 and 74HC138, it is not fully pin-compatible due to differing electrical characteristics and drive strength. Specifically, the CD74ACT138PWR sources/sinks ±24 mA versus ±8 mA for 74HC138 and ±0.4 mA for 74LS138. Interchanging them may overload legacy receivers or fail to drive modern loads. Additionally, ACT-series inputs are TTL-compatible, whereas HC inputs are CMOS-level - risking incorrect logic thresholds. The CD74ACT138PWR should be treated as a functionally equivalent but electrically distinct upgrade requiring validation.
CD74ACT138PWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
CD74ACT138PWR FAQ
1.How can I place an order for CD74ACT138PWR through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74ACT138PWR 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 CD74ACT138PWR reliable?
The price and inventory of CD74ACT138PWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74ACT138PWR is usually 5 days.
3.What payment methods are accepted for CD74ACT138PWR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74ACT138PWR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74ACT138PWR?
CD74ACT138PWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74ACT138PWR 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 CD74ACT138PWR?
For technical support, including CD74ACT138PWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74ACT138PWR requirements.
6.How does Aetrix verify that CD74ACT138PWR is sourced from the original manufacturer or authorized distributors?
All CD74ACT138PWR 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 CD74ACT138PWR meets industry standards.
7.What is the process for return or replacement of CD74ACT138PWR?
All CD74ACT138PWR units undergo pre-shipment inspection (PSI). If there is an issue with CD74ACT138PWR, 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 CD74ACT138PWR part is unused and in its original packaging.
Return procedure for CD74ACT138PWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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