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Texas Instruments CY74FCT138ATSOC
- Part No.:
- CY74FCT138ATSOC
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
CY74FCT138ATSOC.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:426
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Product details
Overview
CY74FCT138ATSOC from Texas Instruments is a 1-of-8 active-low decoder IC with three address inputs (A0–A2), three enable inputs (E1, E2 low-active; E3 high-active), and eight mutually exclusive outputs (O0–O7). It operates at 5 V, delivers 64 mA sink / 32 mA source drive, features Ioff for partial-power-down support, and achieves 5.8 ns max propagation delay across –40°C to +85°C. It is used in memory address decoding and peripheral selection in industrial control logic.
For engineers reviewing the CY74FCT138ATSOC datasheet, CY74FCT138ATSOC pinout, CY74FCT138ATSOC application, or CY74FCT138ATSOC equivalent, key selection criteria include TTL-compatible input thresholds, 3.3 V typical VOH, matched rise/fall times, edge-rate control for noise immunity, and SOIC-16 packaging with Level-1 MSL rating.
Technical Context
This device implements combinational logic decoding using standard positive-logic gate architecture with NAND-based output stages. Its triple-enable structure (E1, E2 low; E3 high) enables hierarchical expansion-e.g., five-line-to-32-line decoding with four devices and one inverter-without external gating.
The internal Ioff circuitry actively disables outputs when VCC = 0 V, limiting reverse current to ±1 µA and enabling safe back-drive during partial power-down. Edge-rate control ensures controlled slew rates, reducing simultaneous switching noise while maintaining full TTL-level compatibility on both inputs and outputs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.75 V to 5.25 V - ensures stable operation within industrial 5 V rail tolerances |
| Propagation Delay | Max 5.8 ns (A→O, E→O) - supports high-speed address decoding in ≤170 MHz systems |
| Output Drive | 64 mA sink / 32 mA source - directly drives multiple TTL loads or small LED indicators |
| Ioff Current | ±1 µA at VCC = 0 V - prevents damaging back-current during hot-insertion or mixed-voltage sequencing |
| Input Thresholds | VIL = 0.8 V, VIH = 2.0 V - fully compatible with legacy TTL and 5 V CMOS logic families |
| ESD Protection | 2000-V HBM, 200-V MM, 1000-V CDM - meets industrial handling robustness requirements |
| Package | SOIC-16 (DW), RoHS-compliant, NIPDAU finish, MSL Level-1 - suitable for reflow assembly without moisture bake |
Pinout & Package
Package: 16-pin SOIC (DW), body width 3.9 mm, lead pitch 1.27 mm, JEDEC MS-012AC compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 15, 16 | A0, A1, A2 | Binary address inputs determining active output (O0–O7) |
| 2, 3 | E1, E2 | Active-low enable inputs - both must be low for decode to activate |
| 4 | E3 | Active-high enable input - must be high for decode to activate |
| 5–12 | O0–O7 | Active-low decoded outputs - only one asserted per valid input combination |
| 13 | GND | Ground reference for all logic and power domains |
| 14 | VCC | 5 V supply pin - powers internal logic and output drivers |
Key Features
| Feature | Design Value |
|---|---|
| Triple Enable Logic | Enables cascaded 1-of-32 decoding with minimal external components |
| Ioff Partial-Power-Down | Prevents reverse current flow when VCC is off, supporting hot-swap and multi-rail systems |
| Edge-Rate Control | Reduces simultaneous switching noise (SSN) without compromising speed |
| Matched Rise/Fall Times | Ensures symmetrical timing margins in synchronous bus applications |
| TTL-Compatible I/O | Accepts standard TTL input levels and drives TTL loads directly - no level-shifting needed |
Applications
| Memory Address Decoding | Peripheral Select Logic |
|---|---|
Use Scenario: Selecting one of eight RAM/ROM chips in a microcontroller-based embedded system with 16-bit address bus. IC Role / Device Role / Timing Role: Translates lower 3 address bits and chip-enable signals into individual chip-select lines. Use Value: Eliminates discrete gate logic, reduces board area, and guarantees deterministic 5.8 ns decode latency. | Use Scenario: Enabling specific UART, SPI, or GPIO expanders in an industrial PLC backplane. IC Role / Device Role / Timing Role: Acts as a static peripheral selector driven by CPU address and control bus. Use Value: Provides noise-immune, TTL-compatible selection with Ioff protection during module hot-swap. |
| Bus Expansion Interface | Digital I/O Multiplexing |
Use Scenario: Expanding a 4-bit data bus to control eight independent relay drivers in HVAC control panels. IC Role / Device Role / Timing Role: Converts 3-bit select code into eight parallel enable signals for Darlington arrays. Use Value: Delivers 64 mA sink capability per output - sufficient to drive base inputs without external transistors. | Use Scenario: Routing sensor readout signals from eight analog channels to a single ADC input via analog switches. IC Role / Device Role / Timing Role: Generates mutually exclusive gate-enable pulses synchronized to ADC conversion timing. Use Value: Ensures glitch-free channel selection with matched propagation delays across all outputs. |
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 |
|---|---|---|---|
| CY74FCT138ATSOCT | Tape-and-reel packaging (2000 pcs), identical electrical specs and pinout | Suitable for automated SMT production; same thermal profile (MSL Level-1) | Select when volume assembly requires reel-fed placement |
| SN74FCT138D | Same SOIC-16 package, but FCT138 family variant with 6 ns max delay and 32 mA sink (not 64 mA) | Limited drive strength - insufficient for direct TTL fanout >10 or relay driver bases | Choose only if lower drive and slightly slower timing are acceptable |
Compared with CY74FCT138ATSOC, CY74FCT138ATSOCT offers identical performance in tape-and-reel format for SMT lines, while SN74FCT138D trades 64 mA sink capability for marginally higher timing tolerance - making CY74FCT138ATSOC optimal for high-fanout or noise-sensitive industrial decoding where drive strength and edge control are critical.
Availability
CY74FCT138ATSOC is available at Aetrix Electronics and suitable for industrial control systems, programmable logic interfaces, and memory subsystems requiring stable component supply, long-term lifecycle support, and RoHS-compliant SOIC packaging.
Supply support for CY74FCT138ATSOC 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, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The CY74FCT138ATSOC belongs to TI's FCT logic family, engineered for high-speed, low-noise, TTL-compatible digital interfacing in mission-critical industrial environments.
FAQ
What is the maximum operating temperature range for CY74FCT138ATSOC?
CY74FCT138ATSOC is rated for operation from –40°C to +85°C ambient temperature. This range is validated per the recommended operating conditions table in the official Texas Instruments datasheet SCCS013B, and applies specifically to the SOIC-packaged CY74FCT138ATSOC variant. Thermal derating is not required within this span.
Does CY74FCT138ATSOC support partial power-down mode?
Yes, CY74FCT138ATSOC supports partial power-down mode via its Ioff feature. When VCC = 0 V, output leakage is limited to ±1 µA, preventing damaging back-current from live buses. This behavior is explicitly specified in the electrical characteristics table and confirmed for the CY74FCT138T series including CY74FCT138ATSOC.
What are the enable logic polarities for CY74FCT138ATSOC?
CY74FCT138ATSOC has three enable inputs: E1 and E2 are active-low, E3 is active-high. All three must be asserted simultaneously (E1 = L, E2 = L, E3 = H) for any output to activate. This triple-enable scheme is documented in the function table and logic diagram of the CY74FCT138ATSOC datasheet.
Is CY74FCT138ATSOC pin-compatible with standard 74LS138 or 74HC138 decoders?
No, CY74FCT138ATSOC is not pin-compatible with 74LS138 or 74HC138. While all are 16-pin DIP/SOIC decoders with identical pin numbering for A0–A2, E1–E3, O0–O7, GND, and VCC, the CY74FCT138ATSOC uses FCT-family drive strength and noise-control circuitry that differ electrically - especially in VOH (3.3 V typ), Ioff, and edge-rate behavior - requiring validation in target systems.
What is the typical VOH voltage for CY74FCT138ATSOC at 32 mA source current?
The typical VOH for CY74FCT138ATSOC is 3.3 V when sourcing 32 mA at VCC = 4.75 V, as specified in the "electrical characteristics" table of the SCCS013B datasheet. This reduced VOH (vs. standard 5 V TTL) improves noise margin in mixed-voltage systems while maintaining full TTL-level compatibility.
CY74FCT138ATSOC Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74FCT
- Package/Case:
- 16-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- 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
CY74FCT138ATSOC FAQ
1.How can I place an order for CY74FCT138ATSOC through Aetrix?
Please submit a Request for Quotation (RFQ) for CY74FCT138ATSOC 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 CY74FCT138ATSOC reliable?
The price and inventory of CY74FCT138ATSOC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CY74FCT138ATSOC is usually 5 days.
3.What payment methods are accepted for CY74FCT138ATSOC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CY74FCT138ATSOC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CY74FCT138ATSOC?
CY74FCT138ATSOC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CY74FCT138ATSOC 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 CY74FCT138ATSOC?
For technical support, including CY74FCT138ATSOC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CY74FCT138ATSOC requirements.
6.How does Aetrix verify that CY74FCT138ATSOC is sourced from the original manufacturer or authorized distributors?
All CY74FCT138ATSOC 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 CY74FCT138ATSOC meets industry standards.
7.What is the process for return or replacement of CY74FCT138ATSOC?
All CY74FCT138ATSOC units undergo pre-shipment inspection (PSI). If there is an issue with CY74FCT138ATSOC, 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 CY74FCT138ATSOC part is unused and in its original packaging.
Return procedure for CY74FCT138ATSOC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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