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Texas Instruments SN74ALS245AN
- Part No.:
- SN74ALS245AN
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS245AN.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,095
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Product details
Overview
SN74ALS245AN 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-compatible systems. It operates from 4.5 V to 5.5 V, delivers max propagation delay of 5.5 ns at 5 V, supports 12 mA low-level output drive (24 mA typical), and features pnp inputs to reduce DC loading. It is used in legacy industrial control backplanes and microprocessor system address/data bus isolation.
For engineers reviewing the SN74ALS245AN datasheet, SN74ALS245AN pinout, SN74ALS245AN application, or SN74ALS245AN equivalent, key selection criteria include its 20-pin PDIP package, direction-control (DIR) and output-enable (OE) logic interface, guaranteed 3-state isolation timing (tPZH/tPZL ≤ 20 ns), and compatibility with ALS logic family voltage thresholds (VIH = 2 V, VIL = 0.8 V).
Technical Context
The SN74ALS245AN implements dual 8-bit bidirectional data paths controlled by a single DIR input and a shared OE input. Its internal architecture uses bipolar ALS (Advanced Low-power Schottky) technology, enabling fast switching while maintaining TTL-compatible input thresholds and output drive capability.
Directional data flow is determined solely by DIR: low enables B→A transmission, high enables A→B transmission. OE must be low for either path to be active; when high, all outputs enter high-impedance state with tPHZ/tPLZ ≤ 10 ns and tPZH/tPZL ≤ 20 ns, ensuring clean bus isolation during arbitration or power sequencing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures robust operation across standard TTL supply tolerances and brown-out conditions. |
| Max Propagation Delay | 5.5 ns at VCC = 5 V - Enables reliable operation in 100+ MHz bus clock domains with margin. |
| IOL (Low-Level Output) | 12 mA min - Drives standard TTL loads directly without external buffers in point-to-point or lightly loaded buses. |
| VIH / VIL | 2.0 V / 0.8 V - Matches TTL logic thresholds, allowing direct interfacing with 74LS/74ALS/74F families. |
| 3-State Enable/Disable Time | tPHZ ≤ 10 ns, tPZH ≤ 20 ns - Guarantees rapid, glitch-free bus release during multi-master arbitration. |
| Input DC Loading | pnp input structure - Reduces input current to ≤ 0.1 mA, minimizing bus loading and fanout constraints. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial-grade embedded systems and industrial control panels. |
Pinout & Package
SN74ALS245AN is housed in a 20-pin plastic dual in-line package (PDIP-N), 0.300-inch wide, with standard through-hole mounting and JEDEC MS-001 compliant footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B bus data flows to A bus; High = A bus data flows to B bus - determines data path polarity. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines connected to one bus segment; high-impedance when OE = high or DIR conflicts. |
| 10 (GND) | Ground Reference | Primary signal and power return path; must be low-inductance connection for noise immunity. |
| 11 (VCC) | Power Supply | +5 V supply pin; requires local 0.1 µF ceramic decoupling adjacent to pin. |
| 12 (OE) | Output Enable Input | Low = outputs active; High = all A/B pins enter 3-state - primary bus isolation control. |
| 13–20 (B1–B8) | Port B I/O Terminals | Bidirectional data lines connected to second bus segment; functionally identical to A-side under DIR control. |
Key Features
| Feature | Design Value |
|---|---|
| ALS Bipolar Technology | Combines speed (5.5 ns tpd) with low power consumption vs. standard LS, enabling higher-density bus interfaces. |
| 3-State Bus Driving | Outputs drive bus lines directly without pull-up resistors, reducing component count and board space in multi-drop systems. |
| pnp Input Structure | Reduces input current to ≤ 0.1 mA per control input, lowering total bus loading and simplifying fanout calculations. |
| Asynchronous Bidirectional Control | Single DIR line eliminates need for separate transmit/receive enable logic, streamlining bus arbitration design. |
| TTL-Compatible Thresholds | VIH = 2.0 V and VIL = 0.8 V ensure interoperability with legacy 74LS, 74F, and microcontroller GPIOs without level shifters. |
Applications
| Microprocessor System Bus Isolation | Industrial Backplane Data Routing |
|---|---|
Use Scenario: Isolating CPU address/data bus from peripheral expansion slots in legacy x86 or Z80-based controllers. IC Role / Device Role / Timing Role: Bidirectional transceiver managing data flow between CPU and I/O cards, controlled by CPU address decode and bus grant signals. Use Value: Prevents bus contention during DMA or interrupt-driven transfers; 5.5 ns propagation delay ensures cycle timing compliance at 10–20 MHz bus speeds. | Use Scenario: Routing sensor data and control commands across modular PLC backplanes with mixed-vendor modules. IC Role / Device Role / Timing Role: Level-shifting and direction-controlled bridge between isolated 5 V logic domains on separate backplane segments. Use Value: Enables hot-swap-safe bus isolation via OE control; pnp inputs minimize loading on long, unterminated backplane traces. |
| Legacy Instrumentation Data Interface | Test Equipment Signal Multiplexing |
Use Scenario: Interfacing GPIB or IEEE-488 controller logic to instrument-specific parallel data ports in benchtop analyzers. IC Role / Device Role / Timing Role: Translating and buffering parallel command/status words between controller and device-specific register maps. Use Value: Guaranteed 3-state disable timing (tPZH ≤ 20 ns) prevents glitches during command handshaking sequences. | Use Scenario: Multiplexing multiple DUT (device-under-test) digital I/O lines onto a shared test head interface in ATE systems. IC Role / Device Role / Timing Role: Bidirectional channel selector enabling one test controller to communicate with up to eight DUTs via time-division. Use Value: 12 mA output drive supports driving multiple CMOS inputs simultaneously; DIR/OE dual control allows precise per-cycle direction management. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS245N | Faster propagation delay (7.5 ns max), higher IOL (48 mA), but increased ICC (95 mA vs. 55 mA) and higher input leakage (±0.75 mA). | Better suited for high-speed, heavily loaded buses where timing margin is critical and power budget allows. | Select SN74AS245N only if system requires sub-8 ns tpd and can accommodate higher supply current and thermal dissipation. |
| SN74LS245N | Slower (20 ns max tpd), lower drive (8 mA IOL), but lower ICC (36 mA) and wider availability in legacy stock. | Preferred for cost-sensitive, low-speed upgrades where timing slack exists and power efficiency is prioritized. | Choose SN74LS245N for drop-in replacement in non-critical timing paths or where ALS speed is unnecessary. |
Compared with SN74ALS245AN, SN74AS245N offers superior speed and drive at higher power cost, while SN74LS245N trades performance for lower power and broader legacy support-making SN74ALS245AN the balanced choice for mid-speed industrial bus isolation.
Availability
SN74ALS245AN is available at Aetrix Electronics and suitable for industrial control backplanes, legacy microprocessor system upgrades, and test equipment signal routing requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS245AN 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 90 years of innovation in industrial, automotive, and communications markets.
The SN74ALS245AN belongs to TI's legacy 74ALS logic family, engineered specifically for high-reliability, medium-speed bus interfacing in commercial-temperature industrial and instrumentation systems.
FAQ
What is the maximum operating temperature range for the SN74ALS245AN?
The SN74ALS245AN is rated for operation from 0°C to +70°C, meeting commercial-grade environmental specifications. This range supports deployment in enclosed industrial cabinets, laboratory instruments, and office-based test equipment where ambient temperatures remain within standard room-temperature bounds. The device does not support extended or military temperature ranges; for –55°C to +125°C operation, SN54ALS245A variants in CDIP or CFP packages are required. Thermal derating is not specified beyond this range.
Does the SN74ALS245AN support true bidirectional data flow on each pin pair?
Yes, the SN74ALS245AN supports true bidirectional data flow per A/B pin pair (e.g., A1↔B1), controlled exclusively by the DIR input. When DIR = low, data passes from B to A; when DIR = high, data passes from A to B. Both directions operate with identical propagation delay (tPLH/tPHL ≤ 10 ns) and output drive capability. No internal latching or direction-hold circuitry is present - direction changes are immediate and synchronous with DIR transitions.
Can unused inputs on the SN74ALS245AN be left floating?
No, all unused inputs on the SN74ALS245AN-including DIR and OE-must be externally tied to VCC or GND to ensure predictable operation and prevent increased ICC or oscillation. Floating TTL inputs exhibit undefined logic states due to high input impedance and susceptibility to noise. TI explicitly recommends hard-wiring unused control inputs per SCBA004 application report; leaving them unconnected may cause erratic 3-state behavior or excessive power draw.
What is the recommended decoupling for the SN74ALS245AN VCC pin?
A minimum 0.1 µF ceramic capacitor placed as close as possible to the SN74ALS245AN VCC pin (pin 11) and GND (pin 10) is required for stable operation. For systems with multiple SN74ALS245AN devices or high-frequency bus activity, add a bulk 4.7 µF–10 µF tantalum or aluminum electrolytic capacitor near the power entry point. Avoid shared vias between decoupling caps and signal traces; use short, direct connections to minimize inductance and suppress switching noise-induced ground bounce.
Is the SN74ALS245AN pin-compatible with the SN74AS245N?
Yes, the SN74ALS245AN and SN74AS245N share identical 20-pin PDIP (N) package dimensions, pinout, and terminal functions-including DIR, OE, A1–A8, B1–B8, VCC, and GND. However, they are not functionally interchangeable without validation: SN74AS245N draws significantly higher supply current (95 mA vs. 55 mA) and has different input leakage (±0.75 mA vs. ±0.1 mA), which may affect bus loading and thermal design. Electrical substitution requires full system-level timing and power review.
SN74ALS245AN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- 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:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74ALS245AN FAQ
1.How can I place an order for SN74ALS245AN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS245AN 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 SN74ALS245AN reliable?
The price and inventory of SN74ALS245AN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS245AN is usually 5 days.
3.What payment methods are accepted for SN74ALS245AN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS245AN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS245AN?
SN74ALS245AN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS245AN 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 SN74ALS245AN?
For technical support, including SN74ALS245AN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS245AN requirements.
6.How does Aetrix verify that SN74ALS245AN is sourced from the original manufacturer or authorized distributors?
All SN74ALS245AN 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 SN74ALS245AN meets industry standards.
7.What is the process for return or replacement of SN74ALS245AN?
All SN74ALS245AN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS245AN, 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 SN74ALS245AN part is unused and in its original packaging.
Return procedure for SN74ALS245AN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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