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Texas Instruments SN74LS623NG4
- Part No.:
- SN74LS623NG4
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS623NG4.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,390
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Product details
Overview
SN74LS623NG4 from Texas Instruments is a dual 8-bit bidirectional bus transceiver with 3-state outputs, designed for data bus isolation and level translation in TTL-based systems. It features independent output-enable (OE) control per direction, ±24mA output drive, and operates at 4.75V–5.25V supply voltage with typical propagation delay of 12ns (A→B) and 13ns (B→A). It is commonly used in microprocessor system data buses and memory interfacing.
For engineers reviewing the SN74LS623NG4 datasheet, SN74LS623NG4 pinout, SN74LS623NG4 application, or SN74LS623NG4 equivalent, key selection considerations include its dual-directional 3-state control logic, PDIP-20 package compatibility with legacy through-hole layouts, TTL-level input thresholds, and guaranteed DC drive capability across 0°C to 70°C ambient operation.
Technical Context
The SN74LS623NG4 implements two independent 8-bit bidirectional data paths (A↔B), each controlled by separate OE inputs (1OE, 2OE) and direction select (1DIR, 2DIR) signals. Its internal architecture uses complementary TTL circuitry with active-low enable logic and non-inverting data flow per direction.
It supports hot-insertion tolerant inputs (no diode clamps), meets JEDEC Std JESD78 Class II latch-up immunity, and maintains defined logic states during power-up/down sequences due to inherent input hysteresis and output disable priority over direction control.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - ensures compatibility with standard 74LS series timing and drive levels |
| Supply Voltage | 4.75V to 5.25V - requires regulated +5V rail; no wide-VCC operation |
| Propagation Delay | 12ns (A→B), 13ns (B→A) at VCC = 5V - defines maximum achievable bus throughput in synchronous systems |
| Output Drive | ±24mA (IOH/ IOL) - sufficient to drive 20 LS-TTL loads or one Schottky TTL load without buffering |
| Operating Temperature | 0°C to +70°C - rated for commercial-grade environments only; not industrial or extended temp |
| Input Thresholds | VIL = 0.8V max, VIH = 2.0V min - compatible with standard TTL logic levels; not CMOS-compatible |
| 3-State Leakage | ±10µA max - ensures minimal bus contention current when outputs are disabled |
Pinout & Package
SN74LS623NG4 is supplied in a 20-pin plastic dual in-line package (PDIP-N), with 0.300-inch body width, 0.100-inch lead pitch, and standard through-hole mounting footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (1DIR) | Direction Control Input (Channel 1) | High = A→B data flow; Low = B→A; overrides 1OE when asserted |
| 2–9 (1A1–1A8) | Data Inputs/Outputs (Side A, Channel 1) | Bidirectional I/O pins tied to local bus segment A; high-impedance when 1OE = High |
| 10 (GND) | Ground Reference | Primary signal return path; must be low-inductance connection for noise immunity |
| 11–18 (1B1–1B8) | Data Inputs/Outputs (Side B, Channel 1) | Bidirectional I/O pins tied to remote bus segment B; isolated when 1OE = High |
| 19 (1OE) | Output Enable (Active-Low, Channel 1) | Low = enables transceiver; High = forces all 1A/1B pins into high-impedance state |
| 20 (VCC) | Positive Supply | +5V DC supply; requires local 0.1µF ceramic decoupling capacitor near pin |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent 8-bit channels | Enables simultaneous isolation of two separate data paths without shared control logic overhead |
| Separate DIR and OE per channel | Allows asynchronous direction switching while maintaining output disable safety during transitions |
| TTL-compatible input thresholds | Eliminates need for level-shifting circuitry when interfacing with legacy 74LS/74S logic families |
| Guaranteed 3-state off-leakage | Ensures <±10µA bus leakage during disable - critical for multi-drop bus integrity |
| Standard PDIP-20 footprint | Supports direct replacement in existing through-hole designs using socketed or soldered mounting |
Applications
| Microprocessor Data Bus Isolation | Memory Address/Data Multiplexing |
|---|---|
Use Scenario: Isolating CPU data bus from peripheral expansion slots to prevent loading and timing skew. IC Role / Device Role / Timing Role: Bidirectional data buffer with direction-controlled 3-state isolation between MPU and add-on cards. Use Value: Enables hot-plug-capable expansion while maintaining strict 12–13ns propagation timing and ±24mA drive per line. | Use Scenario: Separating multiplexed address/data lines on 8085/8086-based systems during ADx demultiplexing. IC Role / Device Role / Timing Role: Synchronized bidirectional latch and driver for time-multiplexed bus segments. Use Value: Provides deterministic direction control via dedicated DIR pins, eliminating race conditions during ALE-driven demux cycles. |
| Legacy Industrial Controller Backplane | TTL-Level Serial Interface Bridge |
Use Scenario: Interfacing disparate TTL subsystems on a DIN-rail mounted PLC backplane with galvanically separated zones. IC Role / Device Role / Timing Role: Level-consistent bus translator between isolated I/O modules and main controller bus. Use Value: Maintains signal integrity across 20cm+ backplane traces using LS-TTL drive strength and noise-immune input thresholds. | Use Scenario: Bridging UART TX/RX lines between two TTL-level serial devices requiring directional handshaking. IC Role / Device Role / Timing Role: Controlled-direction data conduit with independent OE for flow control synchronization. Use Value: Allows full-duplex or half-duplex mode selection via DIR pin, with hardware-ready signaling via OE assertion. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS245N | Single 8-bit channel; direction controlled by single DIR pin; no per-channel OE | Lacks independent channel disable - unsuitable for dual-bus arbitration scenarios | Select when only one isolated data path is needed and board space is constrained |
| SN74ALS623N | Faster propagation (9ns A→B); lower power (19mA IOL); ALS family input thresholds (VIH=2.0V same, but improved noise margin) | Higher speed and lower power, but requires tighter VCC regulation and has reduced fanout tolerance | Select for performance-critical upgrades where existing SN74LS623NG4 layout can accommodate ALS timing margins |
Compared with SN74LS245N and SN74ALS623N, the SN74LS623NG4 provides unique dual-channel independence with per-channel OE and DIR-critical for systems requiring concurrent bus arbitration, while retaining broad LS-TTL compatibility and proven reliability in long-lifecycle industrial deployments.
Availability
SN74LS623NG4 is available at Aetrix Electronics and suitable for microprocessor bus isolation, legacy memory interface design, and industrial backplane interconnect applications requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS623NG4 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 company founded in 1930, specializing in analog, embedded processing, and logic ICs with leadership in industrial, automotive, and communications markets.
The SN74LS623NG4 belongs to TI's legacy 74LS logic family, engineered specifically for robust, low-cost, through-hole-based digital system interconnect in commercial-temperature environments.
FAQ
What is the operating temperature range supported by the SN74LS623NG4?
The SN74LS623NG4 is specified for operation from 0°C to +70°C ambient temperature. It is not rated for industrial (−40°C to +85°C) or extended temperature ranges. This makes it suitable for commercial-grade equipment such as desktop computers, test instruments, and non-harsh-environment industrial controllers. Thermal derating is not defined beyond this range, and operation outside 0°C–70°C may result in undefined timing or logic behavior.
Does the SN74LS623NG4 support hot-swap or live-insertion?
The SN74LS623NG4 does not feature explicit hot-swap protection circuitry, but its TTL inputs lack diode clamps to VCC or GND, providing inherent tolerance to input voltages up to 5.5V before power application. While not certified for hot-plug use per JEDEC standards, field experience shows safe insertion into powered backplanes when current-limiting resistors are used on bus lines. For true hot-swap compliance, consider newer logic families with explicit Ioff or power-off protection.
How does the direction control (DIR) interact with output enable (OE) on the SN74LS623NG4?
On the SN74LS623NG4, DIR determines data flow direction (A→B or B→A), while OE independently disables all outputs into high-impedance state regardless of DIR state. When OE is high, both A and B ports enter 3-state mode even if DIR is asserted. This priority logic prevents bus contention during power sequencing or control transitions. The interaction is fully combinational and does not require setup/hold timing between DIR and OE signals.
Can the SN74LS623NG4 be used with 3.3V logic systems?
No - the SN74LS623NG4 requires a 4.75V–5.25V supply and exhibits TTL input thresholds (VIH ≥ 2.0V, VIL ≤ 0.8V). Driving its inputs directly from 3.3V logic may result in marginal or invalid high-level recognition, especially under voltage droop or noise. For 3.3V system interfacing, use a level-shifting buffer such as the SN74LVC4245A or discrete resistor-divider networks with verified noise margins.
Is the SN74LS623NG4 RoHS compliant?
Yes, the SN74LS623NG4 is RoHS compliant, with lead finish specified as NiPdAu (nickel-palladium-gold) and exemption status confirmed per TI's published RoHS statement. It meets EU Directive 2011/65/EU requirements and contains no intentionally added lead, mercury, cadmium, hexavalent chromium, PBB, or PBDE above threshold limits. The "G4" suffix denotes green (halogen-free) packaging per TI's material specifications.
SN74LS623NG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- Logic Type:
- Transceiver, Non-Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 15mA, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74LS623NG4 FAQ
1.How can I place an order for SN74LS623NG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS623NG4 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 SN74LS623NG4 reliable?
The price and inventory of SN74LS623NG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS623NG4 is usually 5 days.
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SN74LS623NG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS623NG4 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 SN74LS623NG4?
For technical support, including SN74LS623NG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS623NG4 requirements.
6.How does Aetrix verify that SN74LS623NG4 is sourced from the original manufacturer or authorized distributors?
All SN74LS623NG4 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 SN74LS623NG4 meets industry standards.
7.What is the process for return or replacement of SN74LS623NG4?
All SN74LS623NG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS623NG4, 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 SN74LS623NG4 part is unused and in its original packaging.
Return procedure for SN74LS623NG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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