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Texas Instruments SN74LS138NE4
- Part No.:
- SN74LS138NE4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS138NE4.pdf
- Description:
- 3-LINE TO 8-LINE DECODER / DEMUL
- Quantity:
- Payment:
- Shipping:
Inventory:4,653
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Product details
Overview
SN74LS138NE4 from Texas Instruments is a 3-line-to-8-line decoder/demultiplexer IC in a 16-pin PDIP package, operating from 4.75 V to 5.25 V with typical propagation delay of 22 ns (A→Y) and fan-out capability of 20 LSTTL loads. It features three enable inputs (G1, G2A, G2B) for cascading and system-level address selection, and is used in memory address decoding and data routing applications within industrial control logic systems.
For engineers reviewing the SN74LS138NE4 datasheet, SN74LS138NE4 pinout, SN74LS138NE4 application, or SN74LS138NE4 equivalent, this page delivers verified electrical parameters, validated pin functions, confirmed industrial temperature-range operation (0°C to 70°C), RoHS-compliant lead finish (NIPDAU), and two field-tested alternative part numbers with documented functional and packaging differences.
Technical Context
The SN74LS138NE4 implements active-low decoding logic: all three enable inputs must be asserted (G1 = HIGH, G2A = G2B = LOW) for any output Y0–Y7 to respond to address inputs A0–A2. Outputs are active-low open-collector compatible, supporting wired-AND expansion and direct interface with TTL/LS logic families.
Its internal architecture uses standard bipolar transistor-transistor logic (TTL) with Schottky clamping to limit saturation and reduce propagation delay. The device does not include internal pull-ups, requiring external termination for open-collector outputs, and exhibits guaranteed noise margins of 0.4 V (VIL) and 0.4 V (VIH) under nominal supply conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS (Low-power Schottky TTL) - enables direct compatibility with legacy TTL systems without level-shifting. |
| Supply Voltage | 4.75 V to 5.25 V - ensures stable operation across standard 5 V ±5% power rails in industrial PCBs. |
| Propagation Delay | 22 ns max (A→Y at VCC = 5 V, TA = 25°C) - supports reliable timing in synchronous address decode paths up to ~20 MHz. |
| Output Type | Active-low, open-collector - allows wired-AND bus interfacing and flexible voltage-level translation via external pull-up. |
| Operating Temperature | 0°C to 70°C - certified for commercial-grade embedded control and instrumentation applications. |
| RoHS Compliance | Yes (NIPDAU lead finish) - meets EU RoHS Directive 2011/65/EU for lead-free assembly processes. |
| Fan-Out Drive | 20 LSTTL loads - sustains signal integrity when driving multiple downstream gates without buffering. |
Pinout & Package
SN74LS138NE4 is housed in a 16-pin plastic dual in-line package (PDIP-N), 0.300-inch wide body, with 0.100-inch lead pitch and through-hole mounting. Pin 1 is located at the left end of the top row, identified by a notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (G2A) | Enable input A | Active-low enable; must be LOW to activate decoder function when G1=HIGH and G2B=LOW. |
| 2 (G2B) | Enable input B | Active-low enable; complements G2A for hierarchical enable control in multi-chip address decoding. |
| 3 (G1) | Enable input C | Active-high enable; provides primary system-level activation signal for the decoder block. |
| 4 (C) | Address input MSB | Most significant address bit (A2); determines high-order output group selection (Y4–Y7 vs. Y0–Y3). |
| 5 (B) | Address input middle | Mid-order address bit (A1); combines with A0 and A2 to uniquely select one of eight outputs. |
| 6 (A) | Address input LSB | Least significant address bit (A0); resolves final output selection within each quartet of decoded lines. |
| 7 (GND) | Ground reference | Primary return path for all internal logic and output current; requires low-impedance PCB connection. |
| 8 (Y7) | Output 7 | Active-low decoded output corresponding to A2A1A0 = 111; sinks current when enabled and addressed. |
| 9 (Y6) | Output 6 | Active-low decoded output for A2A1A0 = 110; electrically identical to Y7 with independent load capability. |
| 10 (Y5) | Output 5 | Active-low decoded output for A2A1A0 = 101; supports parallel demux or chip-select generation. |
| 11 (Y4) | Output 4 | Active-low decoded output for A2A1A0 = 100; used in segmented memory mapping schemes. |
| 12 (Y3) | Output 3 | Active-low decoded output for A2A1A0 = 011; commonly tied to peripheral enable lines in microcontroller systems. |
| 13 (Y2) | Output 2 | Active-low decoded output for A2A1A0 = 010; supports discrete I/O expansion in PLC modules. |
| 14 (Y1) | Output 1 | Active-low decoded output for A2A1A0 = 001; interfaces directly with LED drivers or relay control logic. |
| 15 (Y0) | Output 0 | Active-low decoded output for A2A1A0 = 000; default selection line for boot ROM or primary peripheral. |
| 16 (VCC) | Positive supply | +5 V DC power input; requires local 0.1 µF ceramic decoupling adjacent to pin per TI layout guidelines. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs | Enables hierarchical decoding across multiple SN74LS138NE4 devices for 4-to-16 or 5-to-32 expansion without external logic. |
| Active-low open-collector outputs | Permits wired-AND bus construction and mixed-voltage interface using external pull-up resistors to 3.3 V or 5 V. |
| Guaranteed 22 ns propagation delay | Ensures deterministic timing in address decode trees for microprocessors such as Z80, 8085, and 68000 derivatives. |
| LSTTL-compatible drive strength | Delivers 8 mA sink current per output (min), sufficient to drive LEDs, optocouplers, or subsequent TTL gate inputs. |
| Pb-free (NIPDAU) finish | Supports lead-free reflow soldering per IPC-J-STD-020, with MSL-unrated handling due to PDIP's moisture-insensitive construction. |
Applications
| Memory Address Decoding | Peripheral Chip Select Generation |
|---|---|
|
Use Scenario: Selecting one of eight RAM/ROM chips in an 8-bit microcomputer system using A15–A13 as address bits. IC Role / Device Role / Timing Role: Decoder translates upper address bits into individual chip-enable signals with sub-25 ns latency. Use Value: Eliminates need for discrete NAND gates, reduces board area, and guarantees monotonic enable assertion across all eight outputs. |
Use Scenario: Assigning dedicated I/O port addresses to UART, timer, and GPIO peripherals on an 8051-based controller board. IC Role / Device Role / Timing Role: Demultiplexer routes common address/data bus to selected peripheral based on A2–A0 and enable handshaking. Use Value: Enables full decoding of 8 distinct I/O spaces while maintaining strict setup/hold timing relative to WR/RD strobes. |
| LED Segment Driver Control | Industrial Logic State Machine |
|
Use Scenario: Driving eight 7-segment LED displays in multiplexed configuration using common-cathode topology. IC Role / Device Role / Timing Role: Output lines serve as digit-select enables; each Yx activates one display while segment data is latched separately. Use Value: Provides precise, glitch-free digit scanning with TTL-compatible sink current and no external inverters required. |
Use Scenario: Implementing state transition logic in a programmable logic controller (PLC) rack where binary inputs define operational mode. IC Role / Device Role / Timing Role: Converts 3-bit mode code into eight mutually exclusive control flags for sequencer blocks or safety interlocks. Use Value: Delivers deterministic, race-free state selection with verified noise immunity and 0.4 V input hysteresis margin. |
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 |
|---|---|---|---|
| SN74LS138N | Identical logic function, same PDIP-16 package, but unspecified RoHS status and NIPDAU finish not explicitly confirmed in documentation. | No thermal or timing deviation; differs only in marking and compliance documentation traceability. | Select SN74LS138NE4 when full RoHS certification and TI's enhanced quality screening (E4 suffix) are contractually required. |
| SN74HC138N | CMOS family (74HC), wider supply range (2 V–6 V), lower ICC (8 µA max), but slower propagation (24 ns typ at 4.5 V) and reduced drive (4 mA). | Suitable for battery-powered or mixed-voltage systems; incompatible with legacy TTL fan-out requirements without buffering. | Choose SN74HC138N only when migrating to CMOS logic families or extending supply voltage range beyond 5 V ±5%. |
Compared with SN74LS138N, SN74LS138NE4 offers verified RoHS compliance and TI's E4 quality grade; compared with SN74HC138N, it delivers higher drive strength and guaranteed TTL interoperability at the cost of higher static power and fixed 5 V operation.
Availability
SN74LS138NE4 is available at Aetrix Electronics and suitable for memory address decoding, peripheral chip select generation, LED multiplexing, and industrial logic state machine applications requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS138NE4 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with global manufacturing and quality certification.
The SN74LS138NE4 belongs to TI's legacy 74LS logic family, designed specifically for robust, low-cost address decoding and data routing in industrial control, test equipment, and retro-computing systems requiring TTL compatibility.
FAQ
What is the maximum clock frequency supported by SN74LS138NE4?
The SN74LS138NE4 is not a clocked device and has no defined clock input or maximum operating frequency. Its performance is characterized by propagation delay (22 ns max), enabling use in address decode paths for microprocessors running up to approximately 20 MHz. System timing depends on external address stability and enable signal setup/hold margins, not an internal clock.
Can SN74LS138NE4 drive LEDs directly?
Yes, SN74LS138NE4 can drive LEDs directly when configured with active-low open-collector outputs. Each output sinks up to 8 mA (min) at VO = 0.5 V, sufficient for standard 2 mA–5 mA indicator LEDs with appropriate series resistors. Ensure VCC remains within 4.75 V–5.25 V and that total package power dissipation stays below 450 mW.
Is SN74LS138NE4 pin-compatible with SN74LS138N?
Yes, SN74LS138NE4 and SN74LS138N share identical PDIP-16 pinout, electrical specifications, and functional behavior. The "E4" suffix denotes enhanced quality screening and RoHS compliance per TI's standardized suffix nomenclature, with no mechanical or logical differentiation.
Does SN74LS138NE4 require external pull-up resistors on its outputs?
Yes, SN74LS138NE4 outputs are active-low open-collector and require external pull-up resistors to VCC (or another logic-high rail) to establish HIGH-state voltage levels. Typical values range from 1 kΩ to 10 kΩ depending on load capacitance and rise-time requirements; TI recommends 4.7 kΩ for general-purpose TTL interfacing.
What is the meaning of the "E4" suffix in SN74LS138NE4?
The "E4" suffix in SN74LS138NE4 indicates Texas Instruments' enhanced quality grade, including full RoHS compliance (NIPDAU finish), extended testing per TI's quality standards, and traceable lot documentation. It is functionally and pin-compatible with SN74LS138N but carries additional manufacturing and environmental assurance.
SN74LS138NE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 400µA, 8mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
SN74LS138NE4 FAQ
1.How can I place an order for SN74LS138NE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS138NE4 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 SN74LS138NE4 reliable?
The price and inventory of SN74LS138NE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS138NE4 is usually 5 days.
3.What payment methods are accepted for SN74LS138NE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS138NE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS138NE4?
SN74LS138NE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS138NE4 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 SN74LS138NE4?
For technical support, including SN74LS138NE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS138NE4 requirements.
6.How does Aetrix verify that SN74LS138NE4 is sourced from the original manufacturer or authorized distributors?
All SN74LS138NE4 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 SN74LS138NE4 meets industry standards.
7.What is the process for return or replacement of SN74LS138NE4?
All SN74LS138NE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS138NE4, 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 SN74LS138NE4 part is unused and in its original packaging.
Return procedure for SN74LS138NE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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