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Texas Instruments CY74FCT138ATSOCG4
- Part No.:
- CY74FCT138ATSOCG4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
CY74FCT138ATSOCG4.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,670
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Product details
Overview
CY74FCT138ATSOCG4 from Texas Instruments is a 1-of-8 active-low decoder IC with three binary address inputs (A0–A2), three enable inputs (E1, E2 low-active; E3 high-active), and eight mutually exclusive active-low outputs (O0–O7). It delivers 64-mA sink / 32-mA source drive strength, operates at 5 V ±0.25 V over –40°C to +85°C, and supports partial-power-down via Ioff. It is used in memory address decoding and bus expansion circuits in industrial control systems.
For engineers reviewing the CY74FCT138ATSOCG4 datasheet, CY74FCT138ATSOCG4 pinout, CY74FCT138ATSOCG4 application, or CY74FCT138ATSOCG4 equivalent, key selection criteria include propagation delay (max 9 ns), TTL-compatible input thresholds, Ioff-enabled backflow protection, and SOIC-16 package compatibility with legacy 5-V logic systems.
Technical Context
The CY74FCT138ATSOCG4 implements a dual-enable 1-of-8 decoding function with strict timing control: tPLH/tPHL ≤ 9 ns across all input-to-output paths (A→O, E1/E2→O, E3→O), and matched rise/fall times enabled by edge-rate control circuitry. Its logic diagram confirms active-low outputs driven only when E1=L, E2=L, and E3=H - enabling cascaded 1-of-32 decoding using four devices plus one inverter.
It features Ioff circuitry that disables outputs when VCC = 0 V, limiting reverse current to ±1 µA at 4.5 V on outputs - critical for hot-swap and partial-power-down operation. Input hysteresis (Vhys = 0.2 V) improves noise immunity, while VOH = 2.4 V (min) and VOL = 0.55 V (max) at full load ensure robust TTL-level interoperability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.75 V to 5.25 V - ensures stable operation within standard 5-V TTL/CMOS rail tolerances |
| Propagation Delay | ≤9 ns max (A→O, E→O) - enables reliable timing in high-speed address decode paths up to ~110 MHz system clock domains |
| Output Drive | 64 mA sink / 32 mA source - supports direct driving of multiple TTL loads or LED indicators without buffering |
| Ioff Current | ±1 µA at VCC = 0 V - prevents damaging backflow during power sequencing or board hot-plug events |
| Input Thresholds | VIH = 2.0 V min, VIL = 0.8 V max - guarantees full compatibility with standard TTL and 5-V CMOS logic families |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade embedded systems including PLCs and motor controllers |
| ESD Protection | 2000-V HBM, 200-V MM, 1000-V CDM - exceeds JEDEC JESD22 requirements for production reliability |
Pinout & Package
Package: SOIC-16 (DW), 10.75 mm × 6.4 mm body, 1.27 mm pitch, RoHS-compliant NiPdAu lead finish, MSL Level-1 (unlimited reflow).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A0) | Binary address input | LSB of 3-bit address; determines output O0–O7 activation pattern when enabled |
| 2 (A1) | Binary address input | Middle bit of address; combined with A0/A2 selects one of eight outputs |
| 3 (A2) | Binary address input | MSB of address; completes 3-bit decode word for full 1-of-8 selection |
| 4 (E1) | Enable input (active low) | Primary global enable; all outputs forced high unless E1 = L |
| 5 (E2) | Enable input (active low) | Secondary enable; both E1 and E2 must be low for decode to activate |
| 6 (E3) | Enable input (active high) | Tertiary enable; E3 = H required alongside E1=E2=L to assert outputs |
| 7 (O0) | Active-low decoded output | Asserted (low) only when A2A1A0 = 000 and all enables satisfied |
| 8 (GND) | Ground reference | Return path for all internal logic and output drivers; decoupling capacitor required |
| 9 (VCC) | Power supply | +5 V supply rail; bypassing with 0.1 µF ceramic capacitor near pin essential |
| 10 (O1) | Active-low decoded output | Asserted (low) only when A2A1A0 = 001 and enables active |
| 11 (O2) | Active-low decoded output | Asserted (low) only when A2A1A0 = 010 and enables active |
| 12 (O3) | Active-low decoded output | Asserted (low) only when A2A1A0 = 011 and enables active |
| 13 (O4) | Active-low decoded output | Asserted (low) only when A2A1A0 = 100 and enables active |
| 14 (O5) | Active-low decoded output | Asserted (low) only when A2A1A0 = 101 and enables active |
| 15 (O6) | Active-low decoded output | Asserted (low) only when A2A1A0 = 110 and enables active |
| 16 (O7) | Active-low decoded output | Asserted (low) only when A2A1A0 = 111 and enables active |
Key Features
| Feature | Design Value |
|---|---|
| Edge-rate controlled outputs | Reduces simultaneous switching noise (SSN) and EMI in dense PCB layouts without external series resistors |
| Ioff partial-power-down support | Enables safe insertion/removal in live-backplane systems by blocking reverse current when unpowered |
| Matched rise/fall times | Minimizes duty cycle distortion on decoded strobes used for synchronous latch control |
| TTL-compatible input levels | Accepts standard 0.8 V/2.0 V thresholds - eliminates level-shifting in mixed-logic 5-V systems |
| Three independent enable inputs | Allows hierarchical decoding (e.g., chip select + block select + sub-block select) without external gating logic |
Applications
| Memory Address Decoding | Peripheral Select Logic |
|---|---|
Use Scenario: Selecting one of eight RAM/ROM chips in a microcontroller-based data acquisition system with 16-bit address bus. IC Role / Device Role / Timing Role: CY74FCT138ATSOCG4 acts as a 3-bit address decoder mapping A13–A15 to individual chip-select lines, enabling banked memory access. Use Value: 9 ns propagation delay ensures setup/hold timing margins are preserved for 5-V SRAMs operating at ≤25 MHz bus speeds. | Use Scenario: Assigning unique select lines to UART, SPI, ADC, DAC, CAN transceiver, GPIO expander, PWM generator, and watchdog timer in an industrial PLC CPU module. IC Role / Device Role / Timing Role: CY74FCT138ATSOCG4 provides eight dedicated active-low peripheral enables synchronized to address strobe and bus cycle timing. Use Value: 64-mA sink capability directly drives LED status indicators on each peripheral board without added drivers. |
| Bus Expansion Interface | Programmable Logic Glue |
Use Scenario: Expanding a 16-bit data bus to 32 lines using four CY74FCT138ATSOCG4 devices and one inverter for 1-of-32 decoding in test equipment backplanes. IC Role / Device Role / Timing Role: CY74FCT138ATSOCG4 serves as modular decode stage in multi-layer address decoding tree, with enables daisy-chained across stages. Use Value: Matched tPLH/tPHL ensures uniform skew across all 32 outputs, critical for parallel bus integrity at 10+ MHz. | Use Scenario: Replacing discrete NAND/NOR gates in FPGA/CPLD I/O conditioning logic where fixed decode patterns simplify HDL implementation. IC Role / Device Role / Timing Role: CY74FCT138ATSOCG4 supplies deterministic, low-skew active-low enables for configurable I/O banks in legacy programmable logic designs. Use Value: Ioff protection prevents contention when FPGA I/O banks are powered down independently during configuration or sleep modes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 1-of-8 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74FCT138D | Same SOIC-16 package, identical pinout, but rated for 5-V ±5% (4.75–5.25 V); propagation delay 5.8 ns max (faster) | Optimized for commercial-temp (0°C to 70°C) systems; lacks extended industrial temp range (–40°C to 85°C) | Select SN74FCT138D only if ambient temperature stays within 0°C–70°C and faster timing is required. |
| 74ACT138SCX | Higher drive (24 mA source / 24 mA sink), 3.3-V compatible inputs, but no Ioff; SOIC-16, same pinout | Designed for mixed-voltage 3.3/5-V systems; unsuitable for partial-power-down or hot-swap use cases | Choose 74ACT138SCX only when interfacing with 3.3-V controllers and Ioff is not required. |
Compared with SN74FCT138D and 74ACT138SCX, the CY74FCT138ATSOCG4 uniquely combines industrial temperature rating, Ioff-enabled power sequencing safety, and 64-mA sink drive - making it the sole option among these three for ruggedized 5-V embedded control applications requiring hot-swap resilience.
Availability
CY74FCT138ATSOCG4 is available at Aetrix Electronics and suitable for industrial automation, programmable logic interface, and memory subsystem design requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant SOIC packaging.
Supply support for CY74FCT138ATSOCG4 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The CY74FCT138ATSOCG4 belongs to TI's FCT logic family, engineered for high-noise-immunity 5-V digital systems requiring fast propagation, robust drive strength, and power-aware features like Ioff - targeting industrial control, instrumentation, and legacy-compatibility upgrades.
FAQ
What is the maximum propagation delay of the CY74FCT138ATSOCG4 under industrial temperature conditions?
The CY74FCT138ATSOCG4 has a maximum propagation delay of 9 ns across all input-to-output paths (A→O, E1/E2→O, E3→O) over its full operating range of –40°C to +85°C, as specified in the switching characteristics table for the 'AT' speed grade. This value is guaranteed with CL = 50 pF and VCC = 4.75 V to 5.25 V, ensuring timing predictability in real-world industrial environments.
Does the CY74FCT138ATSOCG4 support partial-power-down operation, and how is it implemented?
Yes, the CY74FCT138ATSOCG4 supports partial-power-down operation via its Ioff circuitry. When VCC = 0 V, the outputs are disabled and leakage is limited to ±1 µA even with up to 4.5 V applied externally - preventing damaging current backflow during hot-swap or staggered power sequencing. This feature is explicitly documented in the electrical characteristics table and functional description of the device.
What are the absolute maximum ratings for supply voltage and input voltage on the CY74FCT138ATSOCG4?
The CY74FCT138ATSOCG4 has an absolute maximum supply voltage of –0.5 V to +7 V and DC input voltage range of –0.5 V to +7 V. These ratings apply regardless of power state and define stress limits beyond which permanent damage may occur. Operation must remain within recommended conditions: VCC = 4.75 V to 5.25 V and VIH/VIL = 2.0 V/0.8 V respectively.
Can the CY74FCT138ATSOCG4 drive standard TTL loads directly, and what is its output current capability?
Yes, the CY74FCT138ATSOCG4 can directly drive standard TTL loads. It provides 64-mA sink current and 32-mA source current per output, exceeding the 16-mA sink requirement of standard TTL. This allows it to interface with multiple 74LS or 74F loads without external buffers, as confirmed in the electrical characteristics table under IOL/IOH specifications.
Is the CY74FCT138ATSOCG4 pin-compatible with other members of the FCT138 family, such as CY74FCT138CTSOC?
Yes, the CY74FCT138ATSOCG4 is pin-compatible with CY74FCT138CTSOC and CY74FCT138TQCT because all share the same SOIC-16 (DW) or SSOP-16 (DBQ) footprints and identical pin assignments per the logic diagram and pin description table. However, speed grade ('AT' vs 'CT') and drive strength differ - 'AT' offers 9 ns delay and 64-mA sink, while 'CT' offers 5 ns delay and 32-mA sink - so timing and loading must be re-verified.
CY74FCT138ATSOCG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74FCT
- Package/Case:
- 16-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 32mA, 64mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
CY74FCT138ATSOCG4 FAQ
1.How can I place an order for CY74FCT138ATSOCG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for CY74FCT138ATSOCG4 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 CY74FCT138ATSOCG4 reliable?
The price and inventory of CY74FCT138ATSOCG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CY74FCT138ATSOCG4 is usually 5 days.
3.What payment methods are accepted for CY74FCT138ATSOCG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CY74FCT138ATSOCG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CY74FCT138ATSOCG4?
CY74FCT138ATSOCG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CY74FCT138ATSOCG4 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 CY74FCT138ATSOCG4?
For technical support, including CY74FCT138ATSOCG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CY74FCT138ATSOCG4 requirements.
6.How does Aetrix verify that CY74FCT138ATSOCG4 is sourced from the original manufacturer or authorized distributors?
All CY74FCT138ATSOCG4 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 CY74FCT138ATSOCG4 meets industry standards.
7.What is the process for return or replacement of CY74FCT138ATSOCG4?
All CY74FCT138ATSOCG4 units undergo pre-shipment inspection (PSI). If there is an issue with CY74FCT138ATSOCG4, 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 CY74FCT138ATSOCG4 part is unused and in its original packaging.
Return procedure for CY74FCT138ATSOCG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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