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Texas Instruments SN74HC138DE4
- Part No.:
- SN74HC138DE4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74HC138DE4.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,437
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Product details
Overview
SN74HC138DE4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in SOIC-16 package, operating from 2 V to 6 V, with 15 ns typical propagation delay at 6 V, ±4-mA output drive at 5 V, and active-low outputs enabling memory address decoding and LED column selection in embedded control systems.
For engineers reviewing the SN74HC138DE4 datasheet, SN74HC138DE4 pinout, SN74HC138DE4 application, or SN74HC138DE4 equivalent, this page delivers verified functional modes, thermal metrics for SOIC-16, switching characteristics across voltage rails, and real-world implementation guidance for high-speed decoding and demux tasks.
Technical Context
The SN74HC138DE4 implements a 3-bit binary input (A, B, C) to select one of eight active-low outputs (Y0–Y7), with three enable inputs-G1 (active-high) and G2A/G2B (both active-low)-enabling cascading without external inverters. All outputs are CMOS-compatible and fully buffered.
It operates within –40°C to +85°C ambient temperature, supports up to 10 LSTTL loads per output, and features low input current (≤1 µA max) and quiescent ICC ≤80 µA at 6 V, making it suitable for power-sensitive logic routing in industrial and computing systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 2 V to 6 V - supports mixed-voltage system interfacing and battery-backed operation down to 2 V logic levels. |
| Propagation Delay (tpd) | 15 ns typical at VCC = 6 V - enables synchronization with fast microcontrollers and memory access cycles. |
| Output Drive | ±4 mA at 5 V - sufficient to directly sink LED columns or drive TTL inputs without external buffers. |
| Input Current | ≤1 µA max - minimizes loading on upstream logic and preserves signal integrity in fan-out-critical paths. |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade embedded applications including factory automation and power infrastructure. |
| Package | SOIC-16 (D), 9.90 mm × 3.90 mm - surface-mount compatible with standard reflow profiles and PCB assembly lines. |
| Junction-to-Ambient RθJA | 87.3°C/W - defines thermal derating limits under natural convection; requires board-level copper pour for sustained 6-V operation at full load. |
Pinout & Package
SN74HC138DE4 uses the SOIC-16 (D) package with 9.90 mm × 3.90 mm body size and standard 1.27 mm pitch. Pin numbering follows TI's D-package top-view convention.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A) | Select input A (LSB) | Binary address bit 0; determines least-significant output selection when all enables are active. |
| 2 (B) | Select input B | Binary address bit 1; combined with A and C to uniquely decode one of eight outputs. |
| 3 (C) | Select input C (MSB) | Binary address bit 2; MSB of 3-bit address bus; required for full 8-output resolution. |
| 4 (G2A) | Active-low enable A | One of two active-low enables; must be LOW with G2B and G1 HIGH to activate decoding function. |
| 5 (G2B) | Active-low enable B | Second active-low enable; both G2A and G2B must be LOW for device to respond to A/B/C inputs. |
| 6 (G1) | Active-high enable | Primary enable control; must be HIGH alongside G2A/G2B LOW to permit output activation. |
| 7 (Y7) | Output 7 (MSB) | Active-low decoded output corresponding to A=1, B=1, C=1; sinks current when selected. |
| 8 (GND) | Ground reference | Return path for all internal logic and output currents; must be connected to system ground plane. |
| 9 (Y6) | Output 6 | Active-low output for A=0, B=1, C=1; used in 3-to-8 address expansion or data routing. |
| 10 (Y5) | Output 5 | Active-low output for A=1, B=0, C=1; supports discrete channel selection in multiplexed I/O systems. |
| 11 (Y4) | Output 4 | Active-low output for A=0, B=0, C=1; commonly used in LED matrix row/column scanning. |
| 12 (Y3) | Output 3 | Active-low output for A=1, B=1, C=0; enables peripheral chip select in memory-mapped architectures. |
| 13 (Y2) | Output 2 | Active-low output for A=0, B=1, C=0; provides dedicated enable for auxiliary subsystems. |
| 14 (Y1) | Output 1 | Active-low output for A=1, B=0, C=0; used in sensor array addressing or display driver sequencing. |
| 15 (Y0) | Output 0 (LSB) | Active-low output for A=0, B=0, C=0; default selection when address bus is zero; often tied to boot-enable logic. |
| 16 (VCC) | Supply voltage | Positive rail connection; requires local 0.1-µF ceramic bypass capacitor placed adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables hierarchical decoding: two 74HC138 devices can form a 4-to-16 decoder without external inverters. |
| Active-low outputs | Directly interfaces with N-channel MOSFETs or low-side LED drivers without level-shifting or inversion logic. |
| Low power consumption (≤80 µA ICC) | Reduces standby current in always-on control modules, extending battery life in portable instrumentation. |
| High-speed propagation (15 ns typ @ 6 V) | Meets timing budgets for 20+ MHz address decoding in FPGA co-processor or MCU peripheral expansion. |
| CMOS input compatibility | Accepts TTL- and CMOS-level signals across full 2–6 V supply range, simplifying mixed-logic system integration. |
Applications
| LED Matrix Scanning | Memory Address Decoding |
|---|---|
|
Use Scenario: Driving 8-column cathodes in an 8×8 monochrome LED display using row-scanning technique. IC Role / Device Role / Timing Role: SN74HC138DE4 acts as column-select decoder, asserting one active-low Yx output per scan cycle to enable single column conduction. Use Value: Ensures only one column is active at a time, preventing ghosting and reducing average current per LED while maintaining brightness via PWM-compatible timing. |
Use Scenario: Selecting one of eight peripheral ICs (e.g., ADCs, DACs, GPIO expanders) in a microcontroller-based data acquisition system. IC Role / Device Role / Timing Role: SN74HC138DE4 decodes upper address bits (A2–A0) to generate individual chip-select signals synchronized with bus read/write strobes. Use Value: Eliminates need for discrete NAND gates or PLD logic, reducing BOM count and layout complexity while preserving deterministic access latency. |
| Industrial I/O Expansion | Server Board Management |
|
Use Scenario: Enabling/disabling up to eight isolated digital input channels in a programmable logic controller (PLC) backplane module. IC Role / Device Role / Timing Role: SN74HC138DE4 routes enable signals to optocoupler drivers or analog switch control inputs based on configuration register bits. Use Value: Provides deterministic, glitch-free channel gating with no race conditions during address transitions due to synchronous enable architecture. |
Use Scenario: Routing sensor alerts (temperature, fan fault, voltage rail failure) to dedicated interrupt lines on a server baseboard management controller (BMC). IC Role / Device Role / Timing Role: SN74HC138DE4 demultiplexes a shared interrupt bus into eight dedicated BMC input pins, each mapped to a specific subsystem. Use Value: Enables prioritized interrupt handling without software polling, improving system responsiveness and diagnostic granularity in multi-rack 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 |
|---|---|---|---|
| 74HC238PW | Identical logic function and pinout; TSSOP-16 package (5.00 mm × 4.40 mm), lower RθJA (141.6°C/W), RoHS-compliant NiPdAu finish. | Better suited for space-constrained PCBs; higher thermal resistance requires tighter layout attention for continuous 6-V operation. | Choose when footprint reduction and modern packaging compliance outweigh SOIC-16 rework familiarity. |
| SN74HCT138N | TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max); identical SOIC-16 package and pinout; same 15 ns tpd at 5 V. | Designed for direct interface with legacy 5-V TTL logic families without level shifters; slightly higher ICC (≤160 µA). | Prefer when integrating with older 74LS/74ALS peripherals or where input noise immunity at 5 V is critical. |
Compared with SN74HC138DE4, 74HC238PW offers smaller footprint but demands more careful thermal design, while SN74HCT138N trades wider supply tolerance for guaranteed TTL input compatibility-making each alternative optimal only under specific system-level constraints.
Availability
SN74HC138DE4 is available at Aetrix Electronics and suitable for industrial I/O expansion, LED matrix displays, memory address decoding, and server board management requiring stable component supply across extended product lifecycles.
Supply support for SN74HC138DE4 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 solutions, with over 90 years of innovation in high-reliability components for industrial, automotive, and communications markets.
The SN74HC138DE4 belongs to TI's 74HC logic family, engineered for high-speed, low-power decoding and demultiplexing in memory systems, display controllers, and programmable logic interfaces.
FAQ
What is the maximum supply voltage rating for SN74HC138DE4?
The absolute maximum supply voltage for SN74HC138DE4 is 7 V, but the recommended operating range is 2 V to 6 V per TI's SCLS107G datasheet. Operation above 6 V risks exceeding absolute maximum ratings and may cause irreversible damage or parametric shift. Always limit VCC to ≤6 V in production designs.
Does SN74HC138DE4 support cascading with other decoders?
Yes, SN74HC138DE4 supports cascading via its three enable inputs: G1 (active-high), G2A and G2B (both active-low). By connecting outputs of one SN74HC138DE4 to enables of others, you can build 4-to-16 or 5-to-32 decoders without external inverters-verified in TI's functional mode table and application note SCLA011.
What is the output drive capability of SN74HC138DE4 at 5 V?
At VCC = 5 V, SN74HC138DE4 delivers ±4 mA per output (IOL/IOH), sufficient to drive 10 LSTTL loads or directly sink common-anode LED columns. This value is confirmed in Section 6.7 Electrical Characteristics of the official datasheet under IOH = –4 mA and IOL = 4 mA test conditions.
Can SN74HC138DE4 operate at –40°C?
Yes, SN74HC138DE4 is specified for operation from –40°C to +85°C ambient temperature, as stated in Section 6.3 Recommended Operating Conditions. This industrial temperature grade makes it suitable for outdoor equipment, factory automation, and power infrastructure applications where thermal extremes occur.
Is SN74HC138DE4 pin-compatible with SN74HC238?
No-SN74HC138DE4 (SOIC-16) and SN74HC238 (TSSOP-16) share identical logic functionality and signal pin assignments (A–C, G1–G2B, Y0–Y7, VCC, GND), but differ in physical package dimensions, thermal metrics, and pin pitch. They are functionally interchangeable only with PCB layout revision to accommodate TSSOP-16 footprint.
SN74HC138DE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 5.2mA, 5.2mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74HC138DE4 FAQ
1.How can I place an order for SN74HC138DE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC138DE4 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 SN74HC138DE4 reliable?
The price and inventory of SN74HC138DE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC138DE4 is usually 5 days.
3.What payment methods are accepted for SN74HC138DE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC138DE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC138DE4?
SN74HC138DE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC138DE4 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 SN74HC138DE4?
For technical support, including SN74HC138DE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC138DE4 requirements.
6.How does Aetrix verify that SN74HC138DE4 is sourced from the original manufacturer or authorized distributors?
All SN74HC138DE4 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 SN74HC138DE4 meets industry standards.
7.What is the process for return or replacement of SN74HC138DE4?
All SN74HC138DE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC138DE4, 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 SN74HC138DE4 part is unused and in its original packaging.
Return procedure for SN74HC138DE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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