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Texas Instruments SN74HC138DRG4
- Part No.:
- SN74HC138DRG4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74HC138DRG4.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,343
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Product details
Overview
SN74HC138DRG4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in SOIC-16 package, operating from 2 V to 6 V supply, with typical propagation delay of 15 ns at 6 V and ±4-mA output drive capability at 5 V. It features three enable inputs (two active-low, one active-high) for cascading and implements active-low outputs for direct low-side LED column driving in matrix displays.
For engineers reviewing the SN74HC138DRG4 datasheet, SN74HC138DRG4 pinout, SN74HC138DRG4 application, or SN74HC138DRG4 equivalent, key selection criteria include its 16-pin SOIC footprint, 80-µA maximum ICC quiescent current, 10-LSTTL load drive capacity, and compatibility with high-speed memory decoding and data-routing systems requiring sub-40 ns worst-case propagation delay across temperature.
Technical Context
The SN74HC138DRG4 implements standard CMOS logic with balanced output drive and operates as a binary-select decoder: inputs A (LSB), B, and C (MSB) determine which of eight outputs (Y0–Y7) is driven LOW while all others remain HIGH. Its functional mode requires simultaneous assertion of G1 (HIGH), G2A (LOW), and G2B (LOW) to enable decoding.
Three dedicated enable inputs simplify hierarchical expansion-e.g., two SN74HC138DRG4 devices can form a 24-line decoder without external inverters, and a third with one inverter enables 32-line decoding. The device supports demultiplexing by using any enable input as a data channel when others are statically asserted.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - supports mixed-voltage system interfacing and legacy 5-V TTL compatibility |
| Propagation Delay (tpd) | 15 ns typical at VCC = 6 V, CL = 50 pF - enables use in high-speed memory address decoding where delay must be < memory access time |
| Output Drive | ±4 mA at 5 V - sufficient to directly sink/source standard LSTTL loads without buffering |
| Quiescent Current (ICC) | 80 µA maximum at VCC = 6 V - ensures low static power in battery-backed or energy-sensitive control logic |
| Input Leakage Current | ±1 µA maximum - minimizes unintended bias effects in high-impedance enable or select lines |
| Operating Temperature | –40 °C to +85 °C - qualified for industrial-grade embedded control and automation applications |
Pinout & Package
SN74HC138DRG4 uses a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm with standard 1.27-mm pitch. Pin numbering follows JEDEC MS-012, with pins 1–16 arranged in dual-in-line configuration.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A) | Select input A (LSB) | Binary address bit 0; determines output selection along with B and C |
| 2 (B) | Select input B | Binary address bit 1; used with A and C to decode 3-bit input into 8-line output |
| 3 (C) | Select input C (MSB) | Binary address bit 2; completes 3-bit selection vector for Y0–Y7 activation |
| 4 (G2A) | Active-low enable A | First enable control; must be LOW with G2B and G1 to activate outputs |
| 5 (G2B) | Active-low enable B | Second enable control; complements G2A to reduce external gating in cascaded designs |
| 6 (G1) | Active-high enable | Primary enable; must be HIGH with both G2A and G2B LOW to permit decoding |
| 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 | Logic and power return path; requires low-inductance connection to minimize noise coupling |
| 9 (Y6) | Output 6 | Active-low output for A=0, B=1, C=1; shares same electrical characteristics as Y7 |
| 10 (Y5) | Output 5 | Active-low output for A=1, B=0, C=1; electrically identical to other Yx outputs |
| 11 (Y4) | Output 4 | Active-low output for A=0, B=0, C=1; maintains consistent VOL/VOL specs across all outputs |
| 12 (Y3) | Output 3 | Active-low output for A=1, B=1, C=0; supports simultaneous multi-output drive within IOL limits |
| 13 (Y2) | Output 2 | Active-low output for A=0, B=1, C=0; compatible with open-collector wired-OR configurations |
| 14 (Y1) | Output 1 | Active-low output for A=1, B=0, C=0; designed for direct interface to LED cathodes or gate inputs |
| 15 (Y0) | Output 0 (LSB) | Active-low output for A=0, B=0, C=0; lowest-numbered decoded line, commonly used for default selection |
| 16 (VCC) | Supply voltage | Positive power rail; requires local 0.1-µF ceramic bypass capacitor per TI layout guidelines |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables seamless 24-line decoding without external inverters and simplifies hierarchical memory mapping |
| Active-low outputs (Y0–Y7) | Directly drives LED cathodes in multiplexed displays without level-shifting or external pull-ups |
| Low power consumption (80 µA ICC max) | Reduces thermal load in dense logic arrays and extends battery life in portable control panels |
| High-speed propagation (15 ns typ @ 6 V) | Meets timing budgets in fast SRAM/ROM address decoding where decoder delay must be negligible vs. memory access |
| Wide voltage operation (2–6 V) | Interoperates with 3.3-V microcontrollers and 5-V peripheral buses without level translators |
Applications
| LED Matrix Display Control | Industrial Memory Address Decoding |
|---|---|
|
Use Scenario: Driving column lines of an 8×8 monochrome LED matrix using row scanning with shift registers. IC Role / Device Role / Timing Role: Low-side column selector that activates exactly one Yx output per 3-bit A/B/C input cycle, synchronizing with row driver updates. Use Value: Eliminates need for discrete transistors or MOSFETs per column; leverages active-low outputs to sink LED current directly at up to 4 mA per line. |
Use Scenario: Selecting individual memory banks or peripheral devices in a microcontroller-based industrial PLC backplane. IC Role / Device Role / Timing Role: Address decoder translating upper address bits into chip-select signals for multiple SRAM or I/O expanders. Use Value: Propagation delay ≤38 ns over full temperature range ensures no added wait states in 20-MHz bus cycles; enables deterministic memory access timing. |
| Factory Automation I/O Expansion | Building Management System Logic |
|
Use Scenario: Expanding GPIO count on a programmable logic controller to manage 8-zone HVAC actuators or sensor inputs. IC Role / Device Role / Timing Role: Demultiplexer converting serial control commands into parallel enable signals for relay drivers or analog muxes. Use Value: Three enable inputs allow dynamic partitioning of I/O groups; G1 can serve as global enable while G2A/G2B select sub-banks. |
Use Scenario: Implementing zone-based lighting or security alarm routing in centralized building controllers with limited MCU pins. IC Role / Device Role / Timing Role: Logic-level signal router assigning sensor alerts or command pulses to designated output zones based on encoded address. Use Value: SOIC-16 footprint fits compact PCB layouts; 2–6 V operation matches wide-range building power supplies (e.g., 3.3 V MCU + 5 V sensors). |
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 | TTL-compatible input thresholds (VIH = 2 V min, VIL = 0.8 V max); otherwise identical pinout, timing, and drive | Better suited for mixed 5-V TTL/CMOS systems where input noise margins require stricter VIH/VIL | Choose SN74HCT138DR when interfacing directly with legacy 74LS or 74F logic families without level shifters |
| 74LCX138MTCX | Lower VCC range (2.0–3.6 V only); 24 mA output drive; 3.3-V optimized; different pinout (TSSOP-16) | Targeted for low-voltage portable electronics; not drop-in compatible due to voltage and package mismatch | Choose 74LCX138MTCX only in new 3.3-V-only designs where higher drive and lower ICC justify redesign effort |
Compared with SN74HC138DRG4, SN74HCT138DR offers guaranteed TTL input compatibility at 5 V but no advantage in 3.3-V systems, while 74LCX138MTCX delivers superior speed and drive at 3.3 V but requires board-level changes and cannot operate above 3.6 V.
Availability
SN74HC138DRG4 is available at Aetrix Electronics and suitable for industrial automation, LED display subsystems, and building management systems requiring stable component supply and long-term manufacturability.
Supply support for SN74HC138DRG4 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 decades of experience in industrial-grade logic families.
The SN74HC138DRG4 belongs to the 74HC high-speed CMOS logic family, designed for reliable, low-power decoding and demultiplexing in industrial control, instrumentation, and memory systems.
FAQ
What is the maximum supply voltage rating for SN74HC138DRG4?
The absolute maximum supply voltage for SN74HC138DRG4 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 permanent damage or accelerated parametric drift. For robust long-term reliability, maintain VCC ≤ 6 V in all operating conditions.
Does SN74HC138DRG4 support cascading for larger decoding schemes?
Yes, SN74HC138DRG4 supports cascading via its three enable inputs: G1 (active-high), G2A, and G2B (both active-low). Two devices can implement a 24-line decoder without external inverters; adding a third with one inverter achieves 32-line decoding. This architecture eliminates external logic gates and preserves timing integrity across expanded address spaces.
Can SN74HC138DRG4 drive LEDs directly?
Yes, SN74HC138DRG4 can drive LEDs directly through its active-low outputs (Y0–Y7), each capable of sinking up to 4 mA at 5 V. This makes it ideal for low-side column driving in 8×8 LED matrices. Ensure current-limiting resistors are placed in series with each LED anode to maintain IOL within specification and avoid thermal overstress.
What is the typical propagation delay of SN74HC138DRG4 at 5 V?
The typical propagation delay (tpd) of SN74HC138DRG4 at VCC = 5 V and CL = 50 pF is 18 ns for input-to-output transitions (A/B/C → Yx) and 18 ns for enable-to-output transitions (G1/G2A/G2B → Yx), per Section 6.9 of the SCLS107G datasheet. Worst-case tpd across temperature is 45 ns, enabling use in systems with ≥22 MHz clock domains.
Is SN74HC138DRG4 RoHS compliant?
Yes, SN74HC138DRG4 is RoHS compliant, as confirmed in TI's PACKAGE OPTION ADDENDUM (15-Jul-2026): lead finish is NIPDAU, and RoHS status is marked "Yes". It meets EU Directive 2011/65/EU requirements and contains no intentionally added lead, mercury, cadmium, hexavalent chromium, PBB, or PBDE.
SN74HC138DRG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- 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
SN74HC138DRG4 FAQ
1.How can I place an order for SN74HC138DRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC138DRG4 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 SN74HC138DRG4 reliable?
The price and inventory of SN74HC138DRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC138DRG4 is usually 5 days.
3.What payment methods are accepted for SN74HC138DRG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC138DRG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC138DRG4?
SN74HC138DRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC138DRG4 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 SN74HC138DRG4?
For technical support, including SN74HC138DRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC138DRG4 requirements.
6.How does Aetrix verify that SN74HC138DRG4 is sourced from the original manufacturer or authorized distributors?
All SN74HC138DRG4 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 SN74HC138DRG4 meets industry standards.
7.What is the process for return or replacement of SN74HC138DRG4?
All SN74HC138DRG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC138DRG4, 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 SN74HC138DRG4 part is unused and in its original packaging.
Return procedure for SN74HC138DRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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