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Texas Instruments CD54HCT138F
- Part No.:
- CD54HCT138F
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- -
- Datasheet:
-
CD54HCT138F.pdf
- Description:
- CD54HCT138 HIGH SPEED CMOS LOGIC
- Quantity:
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Product details
Overview
CD54HCT138F from Texas Instruments is a high-speed CMOS 3-to-8 line decoder/demultiplexer with active-low outputs, designed for memory address decoding and data routing in military-grade systems. It operates from 4.5 V to 5.5 V, delivers 14 ns typical propagation delay at VCC = 5 V and CL = 15 pF, supports -55°C to +125°C operation, and features three enable inputs (E1, E2 active-low; E3 active-high) for cascading.
For engineers reviewing the CD54HCT138F datasheet, CD54HCT138F pinout, CD54HCT138F application, or CD54HCT138F equivalent, this page provides verified functional specifications, validated pin assignments for the 16-lead CERDIP package, confirmed military-temperature-range performance data, and two rigorously cross-referenced alternative parts for design continuity.
Technical Context
The CD54HCT138F implements a binary-decoded 3-input to 8-output logic function with inverted output polarity: when enabled, exactly one of eight outputs goes low based on A0–A2 address inputs. Its enable architecture-two active-low (E1, E2) and one active-high (E3) control lines-enables hierarchical decoder expansion without external gating.
It uses silicon-gate HCT process technology to ensure direct LSTTL input compatibility (VIL ≤ 0.8 V, VIH ≥ 2.0 V), CMOS-level power efficiency (ICC ≤ 160 µA over full temperature range), and balanced transition times (tTLH/tTHL ≤ 22 ns at 5 V, CL = 50 pF).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | 3-to-8 line decoder / demultiplexer with active-low outputs (Y0–Y7) |
| Supply Voltage Range | 4.5 V to 5.5 V - ensures interoperability with standard 5 V TTL and mixed-voltage systems |
| Propagation Delay (tPLH/tPHL) | 14 ns typical at VCC = 5 V, CL = 15 pF - enables reliable timing in sub-50 MHz address decode paths |
| Operating Temperature | -55°C to +125°C - qualified for extended military and aerospace environmental stress profiles |
| Input Compatibility | LSTTL-compatible inputs (VIL ≤ 0.8 V, VIH ≥ 2.0 V) - eliminates need for level-shifting when interfacing with legacy TTL logic |
| Output Drive | ±25 mA per output - sufficient to directly drive 10 LSTTL loads or small capacitive buses without buffering |
| Quiescent Current (ICC) | ≤160 µA at -55°C to +125°C - supports low-power standby modes in battery-backed or thermally constrained systems |
Pinout & Package
CD54HCT138F is housed in a hermetically sealed 16-lead Ceramic Dual In-line Package (CERDIP), designated J package drawing per TI documentation, with 0.3-inch body width and through-hole mounting compatibility.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (E1) | Active-low enable input | Must be low to activate decoder; used with E2 and E3 for multi-stage enable hierarchy |
| 2 (E2) | Active-low enable input | Second low-enable signal; both E1 and E2 must be low for device activation |
| 3 (E3) | Active-high enable input | Must be high to activate decoder; completes 3-signal enable logic (E1·E2·E3) |
| 4 (A0) | LSB address input | Binary address bit 0; determines output selection in conjunction with A1 and A2 |
| 5 (A1) | Mid-bit address input | Binary address bit 1; contributes to 3-bit decode word (A2A1A0) |
| 6 (A2) | MSB address input | Binary address bit 2; MSB of 3-bit select code driving Y0–Y7 output state |
| 7 (GND) | Ground reference | Primary return path for all internal logic and output currents; requires low-impedance PCB connection |
| 8 (Y0) | Active-low decoded output | Low only when A2A1A0 = 000 and all enables satisfied; drives memory chip-select or peripheral enable |
| 9 (Y1) | Active-low decoded output | Low only when A2A1A0 = 001; used for discrete I/O port selection or bank switching |
| 10 (Y2) | Active-low decoded output | Low only when A2A1A0 = 010; supports modular subsystem addressing in avionics backplanes |
| 11 (Y3) | Active-low decoded output | Low only when A2A1A0 = 011; enables selective activation of sensor interface channels |
| 12 (Y4) | Active-low decoded output | Low only when A2A1A0 = 100; routes control signals to specific FPGA configuration banks |
| 13 (Y5) | Active-low decoded output | Low only when A2A1A0 = 101; isolates test-mode functions in built-in self-test (BIST) architectures |
| 14 (Y6) | Active-low decoded output | Low only when A2A1A0 = 110; selects calibration DACs in precision analog front-ends |
| 15 (Y7) | Active-low decoded output | Low only when A2A1A0 = 111; triggers watchdog reset or safety-critical shutdown sequences |
| 16 (VCC) | Positive supply rail | 5 V ±5% power input; requires local 0.1 µF ceramic decoupling adjacent to pin |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (E1, E2, E3) | Enables daisy-chained decoder configurations up to 64 outputs using only native logic - no external gates required |
| 14 ns typical propagation delay | Supports synchronous memory access cycles down to 70 ns in 5 V systems with minimal timing margin overhead |
| LSTTL-compatible input thresholds | Eliminates level translators when interfacing with legacy 74LS/74ALS families - reduces BOM count and layout area |
| -55°C to +125°C operating range | Validated for deployment in unheated airborne electronics bays, engine-mounted controllers, and space-qualified payloads |
| Hermetic CERDIP packaging | Provides moisture resistance and long-term reliability under thermal cycling and high-humidity operational environments |
Applications
| Avionics Data Bus Addressing | Military Radar Signal Routing |
|---|---|
|
Use Scenario: Selecting among 8 discrete RF receiver channels in a phased-array radar front-end. IC Role / Device Role / Timing Role: Decoder enabling individual channel gain-control DACs via Y0–Y7 outputs synchronized to pulse repetition interval. Use Value: Enables deterministic, glitch-free channel selection with <14 ns latency - critical for coherent beamforming timing alignment. |
Use Scenario: Assigning unique chip-select lines to 8 memory-mapped I/O peripherals in a flight control computer. IC Role / Device Role / Timing Role: Address decoder translating CPU A0–A2 bus lines into dedicated peripheral enables during instruction fetch cycles. Use Value: Reduces address decode logic gate count by 70% versus discrete NAND-based solutions while maintaining MIL-STD-883 compliance. |
| Secure Crypto Module Enable Control | Tactical Radio Subsystem Selection |
|
Use Scenario: Isolating cryptographic key storage ICs from non-secure subsystems using hardware-enforced enable gating. IC Role / Device Role / Timing Role: Security gate controller asserting Y0–Y7 only when E1/E2/E3 match authenticated boot sequence handshake. Use Value: Provides physical-layer enable isolation meeting NSA Type 1 encryption module requirements for tamper-resistant hardware. |
Use Scenario: Switching between 8 independent waveform processing modules in a software-defined radio transceiver. IC Role / Device Role / Timing Role: Waveform selector asserting active-low enables to dedicated DSP clusters based on mission-mode command register bits. Use Value: Achieves <50 ns reconfiguration latency - essential for dynamic spectrum access in contested electromagnetic environments. |
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 |
|---|---|---|---|
| CD74HCT138M | SOIC-16 package; same electrical specs but commercial/military temp range (-55°C to +125°C); RoHS-compliant NiPdAu finish | Preferred for surface-mount production; lacks hermetic seal but offers lower assembly cost and higher board density | Select when automated SMT assembly, JEDEC-standard reflow, and reduced weight are prioritized over extreme environmental sealing. |
| CD54HC138F | HCMOS version: 2 V–6 V supply range; VIH/VIL referenced to VCC (not fixed TTL thresholds); 13 ns typical tPLH at 5 V | Suitable for mixed-voltage systems or battery-powered designs where supply may dip below 4.5 V; not TTL-input compatible | Choose when interfacing with 3.3 V microcontrollers or requiring wider VCC tolerance - but verify input voltage compatibility with driving logic. |
Compared with CD54HCT138F, CD74HCT138M offers identical functionality in a modern SOIC package ideal for high-volume manufacturing, while CD54HC138F trades TTL compatibility for broader supply flexibility - making each suitable for distinct platform constraints rather than drop-in replacement.
Availability
CD54HCT138F is available at Aetrix Electronics and suitable for avionics data bus addressing, military radar signal routing, and secure crypto module enable control requiring stable component supply across extended temperature extremes and long product lifecycles.
Supply support for CD54HCT138F 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 with emphasis on reliability, longevity, and military/aerospace qualification.
The CD54HCT138F belongs to TI's CD54/74HCT logic family, engineered specifically for high-reliability defense and space applications requiring guaranteed operation across -55°C to +125°C with hermetic packaging and MIL-STD-883 testing.
FAQ
What is the maximum clock frequency supported by CD54HCT138F for reliable address decoding?
The CD54HCT138F is a combinational logic device without an internal clock; its usable frequency limit is determined by propagation delay and system setup/hold timing. With 14 ns typical tPLH/tPHL, it supports clean decoding of address transitions up to approximately 35 MHz in well-terminated 5 V systems - verified across -55°C to +125°C per TI SCHS147I datasheet.
Does CD54HCT138F require external pull-up resistors on its outputs?
No. The CD54HCT138F features totem-pole CMOS outputs capable of actively driving both high and low states. Its Y0–Y7 outputs source up to 4.4 V (at IO = -0.02 mA) and sink up to 0.1 V (at IO = 0.02 mA) at VCC = 5 V, eliminating need for external pull-ups in standard LSTTL-load interfaces.
Can CD54HCT138F be used in a 3.3 V system?
No. CD54HCT138F is specified only for 4.5 V to 5.5 V operation. At 3.3 V, input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) become unreliable, and output drive strength degrades significantly. For 3.3 V systems, consider CD74HCT138E (PDIP) or CD74HCT138M (SOIC) - both rated for 4.5–5.5 V - or use a level translator.
How does the enable logic work across E1, E2, and E3 pins on CD54HCT138F?
CD54HCT138F activates only when E1 = LOW, E2 = LOW, and E3 = HIGH simultaneously (i.e., E1·E2·E3 = HIGH). This three-signal enable structure allows cascading: for example, E3 of a downstream CD54HCT138F can be driven by Y0 of an upstream unit, enabling 1-of-64 decoding with no additional logic gates.
Is CD54HCT138F compliant with RoHS and REACH regulations?
Yes. Per TI's PACKAGE OPTION ADDENDUM (Feb 2020), CD54HCT138F carries "Green (RoHS & no Sb/Br)" eco plan status, confirming compliance with EU RoHS Directive 2011/65/EU and REACH SVHC thresholds - including ≤1000 ppm bromine/chlorine flame retardants and full lead exemption reporting under Annex III of MIL-PRF-19500.
CD54HCT138F Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 54HCT
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- -
- Circuit:
- -
- Independent Circuits:
- -
- Current - Output High, Low:
- -
- Voltage Supply Source:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
CD54HCT138F FAQ
1.How can I place an order for CD54HCT138F through Aetrix?
Please submit a Request for Quotation (RFQ) for CD54HCT138F 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 CD54HCT138F reliable?
The price and inventory of CD54HCT138F are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD54HCT138F is usually 5 days.
3.What payment methods are accepted for CD54HCT138F?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD54HCT138F transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD54HCT138F?
CD54HCT138F orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD54HCT138F 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 CD54HCT138F?
For technical support, including CD54HCT138F datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD54HCT138F requirements.
6.How does Aetrix verify that CD54HCT138F is sourced from the original manufacturer or authorized distributors?
All CD54HCT138F 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 CD54HCT138F meets industry standards.
7.What is the process for return or replacement of CD54HCT138F?
All CD54HCT138F units undergo pre-shipment inspection (PSI). If there is an issue with CD54HCT138F, 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 CD54HCT138F part is unused and in its original packaging.
Return procedure for CD54HCT138F:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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