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Texas Instruments SN74LS399N
- Part No.:
- SN74LS399N
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS399N.pdf
- Description:
- IC MULTIPLEXER 4 X 2:1 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,883
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Product details
Overview
SN74LS399N from Texas Instruments is a quadruple 2-input multiplexer with transparent latch storage, implemented in TTL logic, operating over 0°C to 70°C, with 16-pin PDIP package, 15 ns typical propagation delay, and compatible with standard LS-TTL input/output levels. It enables selective routing of four independent data pairs under common select and enable control in digital control and data path applications.
For engineers reviewing the SN74LS399N datasheet, SN74LS399N pinout, SN74LS399N application, or SN74LS399N equivalent, key selection considerations include its dual-function multiplexing + latching capability, guaranteed fan-out of 20 LS-TTL loads, DC supply current of 24 mA max, and compatibility with legacy 5 V TTL systems requiring deterministic data capture on clocked enable transitions.
Technical Context
The SN74LS399N integrates four independent 2:1 multiplexers, each with an active-high strobe (G) that enables transparent latching of selected inputs when asserted. Each channel features complementary outputs (Y and Y̅), supporting both true and inverted signal paths without external inversion.
Its internal architecture uses bipolar TTL circuitry with Schottky-clamped transistors for speed-power optimization. Input thresholds align with standard LS-TTL (VIH = 2.0 V min, VIL = 0.8 V max), and output drive capability meets LS-TTL sink/source requirements (IOL = 8 mA, IOH = -0.4 mA).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - ensures interoperability with legacy 5 V TTL systems and predictable noise margins |
| Function | Quadruple 2-input multiplexer with transparent latch - allows simultaneous selection and storage of four data bits |
| Propagation Delay | 15 ns max (tpd) at VCC = 5 V - supports synchronous operation up to ~33 MHz in critical paths |
| Supply Voltage | 4.75 V to 5.25 V - tight regulation required to maintain LS-TTL timing and noise immunity |
| Fan-Out | 20 LS-TTL loads - enables direct driving of multiple downstream TTL inputs without buffering |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded and industrial control environments |
| Package | 16-pin PDIP (N) - through-hole mounting compatible with legacy prototyping and repair workflows |
Pinout & Package
SN74LS399N is housed in a 16-pin plastic dual in-line package (PDIP), 0.300-inch width, with standard DIP pin spacing (0.100 inch). Pin 1 is marked by a notch or dot; pins are numbered counter-clockwise from top-left corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 4, 9, 12 | Data Input A (IA) | First input of each 2:1 mux channel - routed to output when S = 0 |
| 2, 5, 10, 13 | Data Input B (IB) | Second input of each 2:1 mux channel - routed to output when S = 1 |
| 3, 6, 11, 14 | Select Input (S) | Common select line for all four channels - determines IA or IB path per channel |
| 7, 8, 15, 16 | Strobe / Enable (G) | Active-high latch enable - captures and holds selected input value on rising edge |
| 17–20 | Not applicable | SN74LS399N has only 16 pins; no pins 17–20 exist |
Key Features
| Feature | Design Value |
|---|---|
| Integrated latch per channel | Eliminates need for external flip-flops when synchronizing multiplexed data to system clock edges |
| Complementary outputs (Y/Y̅) | Provides both true and inverted logic states simultaneously - reduces external inverters in bus arbitration or differential signaling |
| LS-TTL compatible I/O | Direct interface with 74LS, 74ALS, and 74F families without level-shifting or pull-up resistors |
| Low power consumption | 24 mA max ICC at 5 V - significantly lower than original 74-series TTL, easing thermal design in dense logic arrays |
| Guaranteed AC/DC specs | Full parametric testing per SDLS174 datasheet - ensures timing predictability in safety-critical sequencing logic |
Applications
| Industrial Control Sequencing | Legacy Test Equipment Data Routing |
|---|---|
Use Scenario: Selecting sensor inputs or actuator command lines in programmable logic controllers with cycle-synchronized sampling. IC Role / Device Role / Timing Role: Multiplexer + latch acting as a synchronized input selector and hold register for scan-cycle alignment. Use Value: Ensures deterministic capture of analog-to-digital converter outputs or switch status before state-machine evaluation. |
Use Scenario: Routing calibration reference signals or DUT response paths in automated test fixtures with fixed timing windows. IC Role / Device Role / Timing Role: Signal path selector with storage enabling stable test vector application during measurement acquisition. Use Value: Prevents metastability during signal switching by holding selected path until next strobe assertion. |
| Microprocessor Bus Expansion | EPROM Address Decoding Logic |
Use Scenario: Extending address/data bus visibility across multiple peripheral slots using shared select lines. IC Role / Device Role / Timing Role: Dynamic bus segment selector with latch retaining configuration between CPU instruction cycles. Use Value: Reduces bus contention by isolating inactive peripherals while preserving active mapping state. |
Use Scenario: Generating chip-select signals for multiple EPROM banks based on upper address bits. IC Role / Device Role / Timing Role: Address decoder element that latches decoded enable state during memory access window. Use Value: Stabilizes CS assertion during address setup/hold transitions, improving read reliability in slow-memory systems. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multiplexer-with-latch applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS253N | No integrated latch; outputs are purely combinational - requires external latch for storage | Suitable where asynchronous selection suffices and timing-critical capture is handled elsewhere | Choose when latch functionality is unnecessary and board space permits discrete storage |
| SN74LS157N | Single-output per channel (no Y̅); no latch; lower pin count (16-pin still, but different pinout) | Better fit for space-constrained designs needing only true outputs and no inversion | Select when complementary outputs are unused and simplified routing is prioritized |
Compared with SN74LS399N, SN74LS253N offers faster propagation (12 ns) but lacks latching, while SN74LS157N provides identical multiplexing without storage or inverted outputs - making SN74LS399N uniquely suited for applications demanding synchronized, dual-polarity data capture in one device.
Availability
SN74LS399N is available at Aetrix Electronics and suitable for industrial control sequencing, legacy test equipment data routing, microprocessor bus expansion, and EPROM address decoding applications requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS399N 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 solutions with broad industrial and automotive reach.
The SN74LS399N belongs to TI's legacy 74LS logic family, designed specifically for reliable, low-power implementation of combinational and registered logic functions in commercial-grade digital systems.
FAQ
What is the primary function of the SN74LS399N?
The SN74LS399N is a quadruple 2-input multiplexer with transparent latch storage. Each of its four channels selects between two inputs (IA or IB) based on a common select line (S), and latches the result when the strobe (G) is high. This dual capability enables synchronized data routing and hold operations in digital control logic, making it distinct from basic multiplexers like the SN74LS157N or SN74LS253N. The SN74LS399N is widely used where deterministic timing and state retention are required within a single IC.
Does the SN74LS399N support 3.3 V operation?
No, the SN74LS399N is specified only for 4.75 V to 5.25 V operation and is not 3.3 V tolerant. Its LS-TTL input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and output drive characteristics are optimized for 5 V systems. Applying 3.3 V supply risks undefined logic states, excessive current draw, or permanent damage. For mixed-voltage designs, level translators or modern 3.3 V-compatible alternatives such as the SN74LVC157A should be considered instead of the SN74LS399N.
How does the latch behavior of the SN74LS399N differ from standard flip-flops?
The SN74LS399N implements transparent latching: when the strobe (G) is high, outputs follow selected inputs in real time; when G goes low, the last-selected value is held. Unlike edge-triggered D-flip-flops, it has no clock input and no setup/hold timing relative to a clock edge - instead, it responds directly to the enable signal level. This makes the SN74LS399N ideal for applications where data stability must be controlled by a simple enable pulse rather than a synchronous clock domain, as seen in many legacy controller and test system architectures using the SN74LS399N.
Are complementary outputs (Y and Y̅) available on all four channels of the SN74LS399N?
Yes, the SN74LS399N provides true (Y) and inverted (Y̅) outputs for each of its four independent multiplexer-latch channels. Pins 1–2, 4–5, 9–10, and 12–13 correspond to IA/IB inputs; pins 3, 6, 11, and 14 are select (S); pins 7, 8, 15, and 16 are strobe (G); and the Y/Y̅ outputs appear on dedicated pins per channel as defined in the official SDLS174 datasheet. This dual-output capability eliminates the need for external inverters in applications requiring both logic polarities - a key functional advantage distinguishing the SN74LS399N from single-output alternatives.
Can the SN74LS399N be used as a replacement for the SN54LS399J in commercial applications?
The SN74LS399N is the commercial-grade version (0°C to 70°C) of the same functional device as the military-grade SN54LS399J (–55°C to 125°C), sharing identical logic behavior, pinout, and AC/DC specifications within its temperature range. While they are not drop-in replacements due to differing temperature ratings and packaging (PDIP vs CDIP), the SN74LS399N is fully suitable for commercial applications where extended temperature operation is unnecessary. System designers using the SN74LS399N benefit from RoHS compliance and cost-effective through-hole assembly - unlike the SN54LS399J, which uses SnPb lead finish and targets harsh-environment use cases.
SN74LS399N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- Multiplexer
- Circuit:
- 4 x 2:1
- 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
SN74LS399N FAQ
1.How can I place an order for SN74LS399N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS399N 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 SN74LS399N reliable?
The price and inventory of SN74LS399N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS399N is usually 5 days.
3.What payment methods are accepted for SN74LS399N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS399N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS399N?
SN74LS399N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS399N 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 SN74LS399N?
For technical support, including SN74LS399N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS399N requirements.
6.How does Aetrix verify that SN74LS399N is sourced from the original manufacturer or authorized distributors?
All SN74LS399N 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 SN74LS399N meets industry standards.
7.What is the process for return or replacement of SN74LS399N?
All SN74LS399N units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS399N, 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 SN74LS399N part is unused and in its original packaging.
Return procedure for SN74LS399N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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