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Texas Instruments SN74LS245NS
- Part No.:
- SN74LS245NS
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74LS245NS.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:752
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Product details
Overview
SN74LS245NS from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in TTL-level systems. It features direction control (DIR), active-low output enable (OE), 8 ns typical propagation delay, ±15 mA high-level/24 mA low-level output drive, and operates at 4.75–5.25 V supply. It is used in industrial backplane interfaces and legacy embedded bus expansion.
For engineers reviewing the SN74LS245NS datasheet, SN74LS245NS pinout, SN74LS245NS application, or SN74LS245NS equivalent, key selection criteria include 3-state isolation capability, TTL-compatible input thresholds (VIL = 0.8 V, VIH = 2 V), PNP-input bus loading reduction, hysteresis-enhanced noise immunity, and SO-20 package compatibility with through-hole and surface-mount board designs.
Technical Context
The SN74LS245NS implements Schottky transistor logic (LS) to achieve fast switching while maintaining TTL voltage compatibility. Its DIR pin selects data flow direction (A→B or B→A), and OE enables/disables all eight channels simultaneously into high-impedance state - enabling true bus isolation without external logic.
It uses PNP inputs to minimize DC loading on driven buses and incorporates built-in hysteresis (0.2–0.4 V) on A/B-side inputs to improve noise margins in electrically noisy industrial environments. All outputs meet standard TTL sink/source specifications under recommended operating conditions (TA = 0–70°C, VCC = 4.75–5.25 V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | TTL LS - ensures compatibility with legacy 74LS-series systems and predictable timing behavior |
| Supply Voltage | 4.75–5.25 V - narrow range mandates stable 5 V rail; not tolerant of undervoltage or overvoltage |
| Propagation Delay | 8–12 ns - supports up to ~50 MHz bus operation with margin for trace delays and loading |
| Output Drive | –15 mA (IOH), 24 mA (IOL) - sufficient to drive multiple TTL loads or long ribbon cables directly |
| Input Hysteresis | 0.2–0.4 V - increases effective noise immunity on shared bus lines in factory automation settings |
| ESD Rating | ±2500 V HBM - meets standard handling requirements for non-ESD-protected industrial assembly lines |
| Operating Temperature | 0 to 70°C - rated for commercial/industrial indoor environments, not extended or automotive grade |
Pinout & Package
SN74LS245NS is housed in a 20-pin small-outline (SO) package with 12.60 mm × 5.30 mm body size, gull-wing leads, and RoHS-compliant NiPdAu lead finish. It is compatible with standard SOIC footprints but requires verification of thermal pad clearance and reflow profile per Level-1-260°C MSL rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data flow; High = A→B data flow; determines signal path polarity across all 8 channels |
| 2–9 (A1–A8) | Bidirectional I/O (A side) | Connects to source bus; functions as input or output depending on DIR state and OE status |
| 10 (GND) | Ground Reference | Primary return path for all internal logic and output currents; must be low-impedance connection |
| 11–18 (B8–B1) | Bidirectional I/O (B side) | Connects to destination bus; mirrors A-side behavior with reversed pin order (B8 to B1) |
| 19 (OE) | Active-Low Output Enable | Low = all outputs enabled; High = all outputs in high-Z - critical for bus arbitration and hot-swap isolation |
| 20 (VCC) | Power Supply | 5 V nominal supply; requires local 0.1 µF bypass capacitor placed adjacent to pin for noise suppression |
Key Features
| Feature | Design Value |
|---|---|
| 3-State Outputs | Enables full electrical isolation of A and B buses when OE is high - essential for multi-master bus contention avoidance |
| PNP Input Structure | Reduces steady-state DC loading on upstream drivers (e.g., MCUs, FPGAs), preserving signal integrity on lightly terminated lines |
| Hysteresis on Bus Inputs | 0.2–0.4 V threshold window improves noise rejection on shared industrial backplanes subject to EMI and ground bounce |
| Standard '245 Pinout | Ensures drop-in replacement compatibility with other 74LS245 variants and legacy designs using PDIP, SOIC, or SSOP packages |
| TTL-Level Compatibility | Accepts standard TTL input voltages (VIH ≥ 2 V, VIL ≤ 0.8 V) and drives standard TTL loads - no level-shifting required |
Applications
| Industrial Backplane Interface | Legacy System Bus Expansion |
|---|---|
|
Use Scenario: Connecting microcontroller-based master modules to peripheral slave cards across a 200-mm ribbon cable in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional data repeater and bus driver that compensates for signal attenuation and skew introduced by long parallel traces. Use Value: Enables reliable 8-bit data transfer at 10 MHz over unshielded ribbon cable without external termination or buffering. |
Use Scenario: Upgrading aging test equipment with additional I/O slots while retaining original TTL-based motherboard architecture. IC Role / Device Role / Timing Role: Isolation transceiver allowing hot-plug insertion of new daughterboards without disrupting active bus communication. Use Value: Prevents bus contention during card insertion/removal via OE-controlled 3-state disable, eliminating need for system reset. |
| Factory Automation Data Hub | Electronic Point-of-Sale Terminal Interface |
|
Use Scenario: Aggregating sensor data from eight discrete PLC I/O modules onto a central CAN-to-TTL gateway board. IC Role / Device Role / Timing Role: Synchronized octal transceiver synchronizing asynchronous sensor read cycles to a common clock domain. Use Value: Provides deterministic 8 ns propagation delay across all channels - critical for time-aligned sampling in motion control loops. |
Use Scenario: Interfacing a 74LS-based cash register controller to a modern LCD display module requiring higher drive strength. IC Role / Device Role / Timing Role: Level-matched buffer translating weak MCU GPIO outputs into robust TTL bus signals. Use Value: Delivers 24 mA sink current to drive LED backlight segments and 15 mA source current for display data lines reliably. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS245N | Same logic, PDIP-20 package (24.33 × 6.35 mm); higher RθJA (46.1°C/W vs. 74.2°C/W), through-hole only | Preferred for prototyping, manual soldering, or legacy through-hole PCBs; unsuitable for space-constrained SMT layouts | Select SN74LS245N if board design uses through-hole mounting and thermal dissipation is managed via heatsinking or airflow. |
| SN74LS245DW | Same logic, SOIC-20 package (12.80 × 7.50 mm); obsolete status per TI documentation; no current production support | Not recommended for new designs due to discontinuation risk and lack of guaranteed supply continuity | Prefer SN74LS245NS over SN74LS245DW for new designs requiring long-term availability and RoHS compliance. |
Compared with SN74LS245N and SN74LS245DW, the SN74LS245NS offers optimal balance of surface-mount compatibility, thermal performance (RθJA = 74.2°C/W), and active production status - making it the preferred choice for volume-manufactured industrial control boards.
Availability
SN74LS245NS is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus expansion, and factory automation data hubs requiring stable component supply across multi-year production cycles.
Supply support for SN74LS245NS 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 solutions with over 50 years of TTL and LS-family product heritage.
The SN74LS245NS belongs to TI's legacy 74LS logic portfolio, engineered specifically for robust, low-cost bidirectional bus interfacing in industrial and commercial systems where reliability and pin compatibility outweigh advanced feature sets.
FAQ
What is the maximum operating temperature range for the SN74LS245NS?
The SN74LS245NS is specified for operation from 0°C to +70°C ambient temperature. This commercial-grade rating makes it suitable for indoor industrial enclosures and office-based electronic point-of-sale terminals but excludes use in under-hood automotive or outdoor uncontrolled environments. Thermal derating is not defined beyond this range, and junction temperature must remain below 150°C under all operating conditions.
Does the SN74LS245NS support bidirectional data flow without external logic?
Yes, the SN74LS245NS supports fully bidirectional data flow using only its DIR pin: when DIR is low, data flows from B-side to A-side; when DIR is high, data flows from A-side to B-side. No external gates or latches are needed to configure direction - the internal logic handles polarity reversal synchronously across all eight channels.
Can the SN74LS245NS be used with 3.3 V logic systems?
No, the SN74LS245NS is not compatible with 3.3 V logic. It requires a 4.75–5.25 V supply and has TTL input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) that do not reliably interface with 3.3 V CMOS outputs. Using it with 3.3 V systems risks marginal switching, increased power consumption, and potential damage due to input voltage violations.
How does the hysteresis in the SN74LS245NS improve noise immunity?
The SN74LS245NS provides 0.2–0.4 V of hysteresis on its A and B bus inputs, meaning the rising and falling input thresholds differ. This prevents oscillation or chatter during slow-rising/falling edges or in presence of bus noise, effectively widening the noise margin by up to 400 mV - especially valuable in electrically noisy factory automation settings.
Is the SN74LS245NS pin-compatible with other 74LS245 package variants?
Yes, the SN74LS245NS shares the industry-standard '245 pinout across all package types (SO, PDIP, SOIC, SSOP). Pin 1 is DIR, pins 2–9 are A1–A8, pin 10 is GND, pins 11–18 are B8–B1 (reversed order), pin 19 is OE, and pin 20 is VCC - enabling direct substitution between SN74LS245NS, SN74LS245N, and SN74LS245DBR in existing layouts.
SN74LS245NS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74LS245NS FAQ
1.How can I place an order for SN74LS245NS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS245NS 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 SN74LS245NS reliable?
The price and inventory of SN74LS245NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS245NS is usually 5 days.
3.What payment methods are accepted for SN74LS245NS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS245NS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS245NS?
SN74LS245NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS245NS 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 SN74LS245NS?
For technical support, including SN74LS245NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS245NS requirements.
6.How does Aetrix verify that SN74LS245NS is sourced from the original manufacturer or authorized distributors?
All SN74LS245NS 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 SN74LS245NS meets industry standards.
7.What is the process for return or replacement of SN74LS245NS?
All SN74LS245NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS245NS, 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 SN74LS245NS part is unused and in its original packaging.
Return procedure for SN74LS245NS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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