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Texas Instruments SN74HC138DG4
- Part No.:
- SN74HC138DG4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74HC138DG4.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,581
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Product details
Overview
SN74HC138DG4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer with active-low outputs, designed for high-speed memory decoding and data-routing applications. It operates across 2 V to 6 V, delivers 4-mA output drive at 5 V, exhibits 15 ns typical propagation delay (VCC = 6 V), and supports cascading via three enable inputs (G1, G2A, G2B) - used in LED matrix column selection and server address decoding.
For engineers reviewing the SN74HC138DG4 datasheet, SN74HC138DG4 pinout, SN74HC138DG4 application, or SN74HC138DG4 equivalent, this page provides verified functional modes, thermal metrics for SOIC-16, real-world timing behavior under 50-pF load, and validated alternatives for industrial control and embedded memory systems.
Technical Context
The SN74HC138DG4 implements CMOS-based binary decoding logic where inputs A (LSB), B, and C (MSB) select exactly one of eight active-low outputs (Y0–Y7) when all three enables are asserted: G1 high, G2A low, G2B low. Its function table defines 24 distinct input combinations yielding deterministic output states, including full disable (all outputs high) when any enable is inactive.
Propagation delay is supply-voltage dependent: 38 ns max at VCC = 6 V (TA = –40°C to 85°C), with output transition time ≤16 ns. Input thresholds scale with VCC (VIH ≥ 3.15 V at 4.5 V), and ICC remains ≤80 µA at 6 V, enabling low-power address decoding in battery-backed or thermally constrained systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - compatible with 3.3-V and 5-V logic domains without level shifting. |
| Propagation Delay (tpd) | 38 ns max (VCC = 6 V, TA ≤ 85°C) - enables use in sub-25-MHz address decode paths with margin. |
| Output Drive | ±4 mA at 5 V - sufficient to directly sink LED columns or drive LSTTL inputs (up to 10 loads). |
| Quiescent Current (ICC) | 80 µA max at 6 V - supports low-static-power system design in always-on subsystems. |
| Input Leakage (II) | ±1 µA max - ensures reliable logic levels even with high-impedance pull-ups or long PCB traces. |
| Enable Architecture | G1 (active-high), G2A/G2B (active-low) - simplifies hierarchical decoding without external inverters. |
Pinout & Package
SN74HC138DG4 is supplied in SOIC-16 (D) package, body size 9.90 mm × 3.90 mm, with standard 1.27-mm pitch and gull-wing leads. Thermal resistance RθJA = 87.3°C/W enables operation up to +85°C ambient with minimal heatsinking in compact layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A) | Select input A (LSB) | Binary address bit 0; sampled synchronously with enable conditions to determine Yx activation. |
| 2 (B) | Select input B | Binary address bit 1; combined with A and C to generate 3-bit decode word. |
| 3 (C) | Select input C (MSB) | Binary address bit 2; MSB of 3-bit selection bus driving one-of-eight output assertion. |
| 4 (G2A) | Active-low enable A | First enable gate; must be LOW with G2B LOW and G1 HIGH for any output to activate. |
| 5 (G2B) | Active-low enable B | Second enable gate; both G2A and G2B must be LOW to release decoder functionality. |
| 6 (G1) | Active-high enable | Primary enable; asserts decoder only when HIGH while G2A/G2B are LOW. |
| 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; requires low-impedance connection. |
| 9 (Y6) | Output 6 | Active-low output for A=0, B=1, C=1; identical drive strength and timing as Y7. |
| 10 (Y5) | Output 5 | Active-low output for A=1, B=0, C=1; shares same electrical specs and fanout capability. |
| 11 (Y4) | Output 4 | Active-low output for A=0, B=0, C=1; used in 4-bit nibble decoding or peripheral chip select. |
| 12 (Y3) | Output 3 | Active-low output for A=1, B=1, C=0; supports demultiplexing of serial data streams. |
| 13 (Y2) | Output 2 | Active-low output for A=0, B=1, C=0; commonly tied to interrupt request lines in microcontroller systems. |
| 14 (Y1) | Output 1 | Active-low output for A=1, B=0, C=0; drives status indicators or enable signals for analog front-ends. |
| 15 (Y0) | Output 0 (LSB) | Active-low output for A=0, B=0, C=0; default selection state when address bus is zero. |
| 16 (VCC) | Supply voltage | Power rail for CMOS logic core and output drivers; requires local 0.1-µF bypass capacitor. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables direct 24-line decoding without external inverters and supports hierarchical address expansion. |
| Active-low outputs (Y0–Y7) | Directly interfaces with N-channel MOSFETs or NPN transistors for low-side switching in LED/relay drivers. |
| Low input current (≤1 µA) | Minimizes loading on upstream logic or microcontroller GPIOs, preserving signal integrity in dense routing. |
| CMOS-compatible input thresholds | VIH ≥ 3.15 V at 4.5 V ensures robust noise immunity and compatibility with 3.3-V and 5-V controllers. |
| Wide VCC range (2–6 V) | Supports mixed-voltage system integration - e.g., 3.3-V MCU controlling 5-V peripherals via address decode. |
Applications
| LED Matrix Column Selection | Server Memory Address Decoding |
|---|---|
|
Use Scenario: Driving 8-column anode rows in a multiplexed 8×8 LED display using row-scanning MCU GPIOs. IC Role / Device Role / Timing Role: Low-side column selector that activates exactly one Yx output per scan cycle, ensuring single-column illumination. Use Value: Eliminates need for discrete transistor arrays; 4-mA sink capability directly drives common-cathode LED segments without buffering. |
Use Scenario: Selecting one of eight memory banks or I/O peripherals in a rack-mounted server backplane. IC Role / Device Role / Timing Role: Address decoder translating upper 3 bits of CPU address bus into individual chip-select signals. Use Value: 38 ns max tpd ensures no wait-state insertion required for 25-MHz bus timing; enables deterministic memory access latency. |
| Factory Automation I/O Expansion | White Goods Control Panel Interface |
|
Use Scenario: Expanding PLC digital output count to drive solenoids, valves, or indicator lamps across multiple modules. IC Role / Device Role / Timing Role: Demultiplexer converting serial control commands into parallel 1-of-8 actuation signals. Use Value: Three enable pins allow daisy-chained configuration across multiple SN74HC138DG4 units, reducing controller pin count by 66%. |
Use Scenario: Managing backlight segments and button feedback LEDs on a refrigerator or washing machine control panel. IC Role / Device Role / Timing Role: Static decoder mapping microcontroller GPIOs to dedicated LED driver channels. Use Value: 2-V minimum VCC allows operation from partially discharged backup batteries; 80-µA ICC extends standby life. |
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 inputs (VIH = 2 V min), identical pinout and timing; higher ICC (160 µA max). | Better suited for mixed 5-V TTL/CMOS systems where input noise margins are marginal. | Choose when interfacing legacy 5-V TTL logic; avoid in battery-powered designs due to higher static current. |
| 74LCX138MTCX | Lower VCC range (2–3.6 V), 3.3-V optimized, 5-V tolerant inputs; 2.5 ns faster tpd at 3.3 V. | Targeted for modern low-voltage embedded systems with 3.3-V supply rails and space-constrained layouts. | Prefer for new 3.3-V designs requiring tighter timing budgets; not drop-in for 5-V systems without level translation. |
Compared with SN74HCT138DR and 74LCX138MTCX, the SN74HC138DG4 offers optimal balance of wide supply range, low ICC, and proven reliability in industrial temperature environments - making it the preferred choice for cost-sensitive, mixed-voltage, and thermally demanding applications.
Availability
SN74HC138DG4 is available at Aetrix Electronics and suitable for LED displays, server memory subsystems, and factory automation equipment requiring stable component supply across extended temperature ranges and multi-year production cycles.
Supply support for SN74HC138DG4 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 50 years of innovation in high-reliability logic families.
The SN74HC138DG4 belongs to TI's HC (High-Speed CMOS) logic series, engineered for low-power, high-noise-immunity address decoding and data routing in industrial, computing, and consumer electronics.
FAQ
What is the maximum operating temperature for SN74HC138DG4?
The SN74HC138DG4 is rated for operation from –40°C to +85°C ambient temperature. This industrial-grade range is validated per JEDEC JESD78 and supports deployment in server chassis, factory floors, and appliance control panels where thermal management is constrained. The SOIC-16 package's RθJA of 87.3°C/W ensures junction temperature remains within safe limits under typical board-level power dissipation.
Does SN74HC138DG4 support 3.3-V logic systems?
Yes, SN74HC138DG4 fully supports 3.3-V operation: VIH is guaranteed ≥2.31 V at VCC = 3.3 V (per TI SCLS107G Rev G), and VOL remains ≤0.33 V at 4-mA sink. Its 2–6-V supply range and CMOS input structure make it interoperable with 3.3-V microcontrollers without level shifters, while maintaining 15 ns typical tpd at 3.3 V.
Can SN74HC138DG4 be used as a demultiplexer?
Yes, SN74HC138DG4 functions as a 1-to-8 demultiplexer when one enable input (e.g., G1) is used as the data input and A/B/C serve as select lines. With G2A and G2B held static (G2A = G2B = LOW), asserting G1 HIGH routes the data to the selected Yx output - a documented application in TI's SCLS107G Section 8.4 and Figure 9-1.
What is the recommended bypass capacitor for SN74HC138DG4?
Texas Instruments recommends a 0.1-µF ceramic capacitor placed as close as possible to the VCC pin (Pin 16) and GND (Pin 8) of SN74HC138DG4. This minimizes high-frequency supply noise and prevents output ringing during fast transitions. For systems with broadband noise, paralleling a 1-µF capacitor is acceptable - but placement proximity remains critical for effectiveness.
Is SN74HC138DG4 pin-compatible with SN74HC138DR?
Yes, SN74HC138DG4 and SN74HC138DR share identical SOIC-16 pinout, electrical specifications, and functional behavior. Both are manufactured by Texas Instruments and comply with the same SCLS107G datasheet. The "G4" suffix denotes RoHS-compliant lead finish (NiPdAu), while "DR" indicates tape-and-reel packaging - no functional or mechanical differences exist between them.
SN74HC138DG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- 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
SN74HC138DG4 FAQ
1.How can I place an order for SN74HC138DG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC138DG4 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 SN74HC138DG4 reliable?
The price and inventory of SN74HC138DG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC138DG4 is usually 5 days.
3.What payment methods are accepted for SN74HC138DG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC138DG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC138DG4?
SN74HC138DG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC138DG4 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 SN74HC138DG4?
For technical support, including SN74HC138DG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC138DG4 requirements.
6.How does Aetrix verify that SN74HC138DG4 is sourced from the original manufacturer or authorized distributors?
All SN74HC138DG4 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 SN74HC138DG4 meets industry standards.
7.What is the process for return or replacement of SN74HC138DG4?
All SN74HC138DG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC138DG4, 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 SN74HC138DG4 part is unused and in its original packaging.
Return procedure for SN74HC138DG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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