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Texas Instruments CD74HCT138M96G4
- Part No.:
- CD74HCT138M96G4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
CD74HCT138M96G4.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
CD74HCT138M96G4 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 industrial and embedded systems. It operates at 4.5–5.5 V, delivers 14 ns typical propagation delay (VCC = 5 V, CL = 15 pF), supports -55°C to +125°C operation, and features three enable inputs (E1̅, E2̅, E3) for cascading.
For engineers reviewing the CD74HCT138M96G4 datasheet, CD74HCT138M96G4 pinout, CD74HCT138M96G4 application, or CD74HCT138M96G4 equivalent, key selection criteria include LSTTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V), SOIC-16 package compatibility, and guaranteed operation across extended temperature ranges without derating.
Technical Context
The CD74HCT138M96G4 implements a binary-decoded 3-input (A0–A2) to 8-output logic function with active-low outputs (Y0̅–Y7̅). Its enable architecture uses two active-low (E1̅, E2̅) and one active-high (E3) control signals, allowing hierarchical expansion of decoding trees without external gating logic.
It belongs to the HCT family, ensuring direct DC compatibility with legacy LSTTL logic while retaining CMOS advantages: low static current (≤160 µA over full temperature range), high noise immunity (NIL/NIH = 30% of VCC), and balanced transition times - critical for glitch-free address selection in synchronous memory subsystems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | 3-to-8 line decoder / demultiplexer with active-low outputs (Y0̅–Y7̅) |
| Supply Voltage Range | 4.5 V to 5.5 V - ensures interoperability with standard 5 V TTL and microcontroller I/O rails |
| Propagation Delay | 14 ns typical (VCC = 5 V, CL = 15 pF) - enables reliable operation in sub-50 MHz address decode paths |
| Input Thresholds | VIL ≤ 0.8 V (max), VIH ≥ 2.0 V (min) - guarantees robust recognition of LSTTL output levels |
| Operating Temperature | -55°C to +125°C - qualified for aerospace, automotive under-hood, and industrial control environments |
| Output Drive | ±25 mA per pin - sufficient to directly drive 10 LSTTL loads without buffering |
| Quiescent Current | ≤160 µA (full temp range) - supports low-power standby modes in battery-backed systems |
Pinout & Package
CD74HCT138M96G4 is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package per JEDEC MS-012, with 1.27 mm lead pitch, 3.9 mm body width, and 1.75 mm max height. Pin 1 is marked by a beveled corner or dot.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (E1̅) | Active-low enable input | Must be LOW to activate decoder; used with E2̅ and E3 for multi-level enable hierarchy |
| 2 (E2̅) | Active-low enable input | Second enable input; both E1̅ and E2̅ must be LOW when E3 is HIGH for functional enable |
| 3 (E3) | Active-high enable input | Third enable; all three enables must satisfy truth table condition for output activation |
| 4 (A0) | LSB address input | Binary-select bit 0; latched on enable assertion for stable output decoding |
| 5 (A1) | Mid-bit address input | Binary-select bit 1; determines output Y2n+m in conjunction with A0 and A2 |
| 6 (A2) | MSB address input | Binary-select bit 2; selects among eight output groups in 3-bit address space |
| 7 (Y0̅) | Active-low decoded output | Asserted LOW only when A2A1A0 = 000 and all enables satisfied; drives memory chip select or peripheral enable |
| 8 (Y1̅) | Active-low decoded output | Asserted LOW only when A2A1A0 = 001; provides discrete channel selection in demux applications |
| 9 (Y2̅) | Active-low decoded output | Asserted LOW only when A2A1A0 = 010; used for segmented I/O port addressing |
| 10 (Y3̅) | Active-low decoded output | Asserted LOW only when A2A1A0 = 011; supports bank switching in multi-bank memory systems |
| 11 (Y4̅) | Active-low decoded output | Asserted LOW only when A2A1A0 = 100; enables selective peripheral activation in bus architectures |
| 12 (Y5̅) | Active-low decoded output | Asserted LOW only when A2A1A0 = 101; isolates signal paths in test equipment multiplexing |
| 13 (Y6̅) | Active-low decoded output | Asserted LOW only when A2A1A0 = 110; controls power domains in modular embedded systems |
| 14 (Y7̅) | Active-low decoded output | Asserted LOW only when A2A1A0 = 111; serves as final enable in priority-encoded interrupt controllers |
| 15 (GND) | Ground reference | Primary return path for all internal logic and output currents; requires low-impedance PCB connection |
| 16 (VCC) | Positive supply | 5 V nominal supply rail; bypass capacitor (0.1 µF ceramic) required within 5 mm of pin for noise suppression |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (E1̅, E2̅, E3) | Enables seamless cascade of multiple CD74HCT138M96G4 devices for 4-to-16 or 5-to-32 decoding without external gates |
| LSTTL-compatible input thresholds | Eliminates level-shifting requirements when interfacing with legacy 74LS-series logic or microcontroller GPIOs |
| 14 ns typical propagation delay | Supports real-time address decoding in systems with ≤35 MHz clock domains without timing closure issues |
| Extended temperature range (-55°C to +125°C) | Validated for deployment in uncontrolled environments including motor control enclosures and avionics bays |
| Low quiescent current (≤160 µA) | Reduces system-level standby power consumption - critical for battery-operated instrumentation and remote sensors |
Applications
| Memory Address Decoding | Peripheral I/O Port Selection |
|---|---|
Use Scenario: Selecting one of eight SRAM or ROM chips in a microcontroller-based data logger with 64 KB address space. IC Role / Device Role / Timing Role: CD74HCT138M96G4 decodes upper address bits (A13–A15) to assert individual chip-select lines with <14 ns latency. Use Value: Enables deterministic memory access timing and eliminates address aliasing across 8×8 KB banks. | Use Scenario: Routing UART, SPI, and GPIO signals to one of eight sensor modules on a modular environmental monitoring board. IC Role / Device Role / Timing Role: CD74HCT138M96G4 acts as a hardware-controlled demultiplexer, enabling only one sensor interface at a time via decoded address lines. Use Value: Prevents bus contention and reduces EMI by electrically isolating inactive peripherals from shared communication lines. |
| Interrupt Priority Encoding | Industrial PLC I/O Expansion |
Use Scenario: Prioritizing up to eight asynchronous interrupt sources (e.g., limit switches, emergency stops) in a motion controller. IC Role / Device Role / Timing Role: CD74HCT138M96G4 generates encoded interrupt request lines fed into a priority encoder, with enable inputs synchronized to CPU interrupt acknowledge cycles. Use Value: Guarantees sub-20 ns response window for highest-priority events, meeting SIL-2 functional safety timing constraints. | Use Scenario: Expanding digital input capacity of a programmable logic controller by adding eight isolated 24 VDC input channels. IC Role / Device Role / Timing Role: CD74HCT138M96G4 selects one of eight optocoupler input banks based on PLC scan cycle address pointer. Use Value: Reduces component count vs. discrete gating solutions and maintains noise immunity through verified HCT input thresholds. |
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 |
|---|---|---|---|
| SN74HCT138DR | Same logic function, identical pinout, same SOIC-16 package; TI's newer second-source marking with identical AC/DC specs | No functional difference; validated for same industrial temperature range and LSTTL compatibility | Select SN74HCT138DR if dual-sourcing or long-term availability assurance is required |
| 74VHC138M | Higher VCC range (2–5.5 V); lower propagation delay (10 ns typ); not LSTTL-input compatible (VIH min = 3.15 V at 4.5 V) | Suitable for mixed-voltage 3.3 V/5 V systems but requires level translation when driving from 5 V LSTTL outputs | Choose 74VHC138M only when operating below 4.5 V or requiring faster timing - not drop-in compatible with CD74HCT138M96G4 |
Compared with SN74HCT138DR and 74VHC138M, CD74HCT138M96G4 uniquely balances LSTTL input compatibility, extended temperature resilience, and proven field reliability in harsh industrial deployments - making it optimal where legacy interface integrity and environmental robustness are non-negotiable.
Availability
CD74HCT138M96G4 is available at Aetrix Electronics and suitable for memory address decoding, peripheral I/O selection, interrupt prioritization, and industrial PLC expansion requiring stable component supply across extended temperature ranges.
Supply support for CD74HCT138M96G4 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 over 90 years of innovation in high-reliability electronic components.
The CD74HCT138M96G4 belongs to TI's legacy HCT logic family, engineered specifically for seamless integration with legacy TTL systems while delivering CMOS power efficiency and noise immunity - targeting industrial control, test equipment, and aerospace subsystems.
FAQ
What is the maximum operating frequency supported by the CD74HCT138M96G4?
The CD74HCT138M96G4 does not specify a maximum clock frequency because it is a combinational logic device with no internal clock. Its usable speed is determined by propagation delay: 14 ns typical (VCC = 5 V, CL = 15 pF), supporting reliable operation in address decode paths with ≤35 MHz toggle rates. System-level timing must account for worst-case delays across temperature and voltage extremes.
Can the CD74HCT138M96G4 be used with a 3.3 V microcontroller?
No - the CD74HCT138M96G4 requires a 4.5–5.5 V supply and has LSTTL-compatible inputs (VIH ≥ 2.0 V min), but its VIH threshold is specified only for 4.5–5.5 V operation. Driving it directly from a 3.3 V MCU violates input voltage specifications and risks unreliable logic recognition. A level shifter or 3.3 V–tolerant variant like SN74LVC138A is required for 3.3 V systems.
Is the CD74HCT138M96G4 RoHS compliant and lead-free?
Yes - the CD74HCT138M96G4 is RoHS compliant and lead-free, as confirmed by TI's packaging documentation. It uses Green (halogen-free) molding compound and NiPdAu (NIPDAU) lead finish, meeting EU RoHS Directive 2011/65/EU and JEDEC J-STD-020 moisture sensitivity Level-1 (260°C peak reflow).
How many CD74HCT138M96G4 devices can be cascaded for larger decoding?
Multiple CD74HCT138M96G4 devices can be cascaded using their three enable inputs: E1̅ and E2̅ serve as group-select lines from higher-order address bits, while E3 connects to the master enable. For example, two devices decode 4-to-16 lines (using A3 to select between them), and four devices implement 5-to-32 decoding - all without external logic gates due to the dedicated enable architecture.
What is the meaning of the 'G4' suffix in CD74HCT138M96G4?
The 'G4' suffix in CD74HCT138M96G4 indicates TI's green packaging standard: halogen-free (Cl/Br ≤ 1000 ppm) and RoHS-compliant materials, with NiPdAu (NIPDAU) lead finish. It does not denote a functional revision - electrical, thermal, and timing specifications are identical to CD74HCT138M96.
CD74HCT138M96G4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 4mA, 4mA
- 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
CD74HCT138M96G4 FAQ
1.How can I place an order for CD74HCT138M96G4 through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HCT138M96G4 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 CD74HCT138M96G4 reliable?
The price and inventory of CD74HCT138M96G4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT138M96G4 is usually 5 days.
3.What payment methods are accepted for CD74HCT138M96G4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT138M96G4 transactions.
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4.How is shipping managed for CD74HCT138M96G4?
CD74HCT138M96G4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HCT138M96G4 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 CD74HCT138M96G4?
For technical support, including CD74HCT138M96G4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT138M96G4 requirements.
6.How does Aetrix verify that CD74HCT138M96G4 is sourced from the original manufacturer or authorized distributors?
All CD74HCT138M96G4 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 CD74HCT138M96G4 meets industry standards.
7.What is the process for return or replacement of CD74HCT138M96G4?
All CD74HCT138M96G4 units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT138M96G4, 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 CD74HCT138M96G4 part is unused and in its original packaging.
Return procedure for CD74HCT138M96G4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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