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Texas Instruments SN74ALS645A-1N
- Part No.:
- SN74ALS645A-1N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS645A-1N.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:521
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Product details
Overview
SN74ALS645A-1N from Texas Instruments is an octal bidirectional bus transceiver with 3-state outputs in a 20-pin PDIP package, designed for asynchronous two-way data communication between A and B buses. It features direction control (DIR), output enable (OE), ±48 mA low-level output drive at VCC = 4.75–5.25 V, and operates from 0°C to 70°C.
For engineers reviewing the SN74ALS645A-1N datasheet, SN74ALS645A-1N pinout, SN74ALS645A-1N application, or SN74ALS645A-1N equivalent, this device supports legacy TTL-compatible bus isolation, level-shifted bidirectional data routing, and high-current drive in industrial control backplanes, test equipment interfaces, and memory-mapped peripheral interconnects.
Technical Context
The SN74ALS645A-1N implements true TTL logic with active-low OE and active-high DIR inputs to select data flow direction (A→B or B→A). Its 3-state outputs provide high-impedance isolation when OE is high, enabling bus sharing without contention.
It uses bipolar ALS (Advanced Low-Power Schottky) technology, delivering propagation delays as low as 3 ns (tPLH/tPHL) and enable/disable times down to 2 ns (tPZH/tPLZ) under CL = 50 pF, supporting reliable operation in synchronous and asynchronous bus architectures.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures compatibility with standard 5 V TTL power rails and tolerates supply ripple. |
| IOL (max) | 48 mA - Enables direct driving of multiple TTL loads or resistive termination without external buffers. |
| tPLH / tPHL | 3 ns (max) - Supports high-speed bus handshaking up to ~160 MHz effective toggle rate. |
| Operating Temp | 0°C to 70°C - Qualified for commercial-grade embedded systems and instrumentation environments. |
| Package | PDIP-20 - Through-hole mounting compatible with legacy PCB assembly and prototyping breadboards. |
| Logic Family | ALS (Advanced Low-Power Schottky) - Delivers lower power than standard LS while maintaining TTL voltage thresholds and speed. |
| Output Type | 3-State (active-low OE) - Allows dynamic bus arbitration and multi-drop topology support. |
Pinout & Package
SN74ALS645A-1N is housed in a 20-pin plastic dual in-line package (PDIP-N), 300-mil width, with 0.1-inch lead pitch and standard DIP footprint. Pin 1 is marked by a notch or dot at the top-left corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | High = A→B data transfer; Low = B→A transfer; determines signal flow path through internal transceiver logic. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines connected to one bus segment; driven or sensed depending on DIR and OE state. |
| 10 (GND) | Ground Reference | Primary return path for all internal logic and output current; must be low-impedance for noise immunity. |
| 11 (VCC) | Supply Voltage | +5 V DC power input; bypassing with 0.1 µF ceramic capacitor near pin is required for stable operation. |
| 12–19 (B1–B8) | Port B I/O Terminals | Bidirectional data lines connected to second bus segment; functionally mirrored with A-side under DIR control. |
| 20 (OE) | Output Enable Input | Low = outputs active; High = all A/B pins enter high-impedance state, electrically isolating both buses. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional Data Flow | Single DIR pin selects A→B or B→A transfer without external logic, reducing board space and routing complexity. |
| Enhanced Output Drive | 48 mA sink capability enables direct interface to unterminated or lightly loaded TTL/CMOS buses without pull-up resistors. |
| Fast 3-State Switching | tPZH/tPLZ ≤ 5 ns ensures minimal bus turnaround time, critical for high-throughput memory or peripheral access cycles. |
| TTL-Compatible Thresholds | VIH = 2 V, VIL = 0.8 V - Guarantees interoperability with legacy 74LS, 74F, and microcontroller GPIOs. |
| ALS Process Technology | Combines Schottky clamping with low-power design for 36 mA typical ICC (outputs low), improving thermal margin in dense layouts. |
Applications
| Industrial Backplane Interface | Test Equipment Bus Coupling |
|---|---|
Use Scenario: Isolating CPU address/data bus from modular I/O cards in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional transceiver managing synchronous read/write transfers between master and slave slots. Use Value: 48 mA drive sustains signal integrity across 15 cm backplane traces; 3-state isolation prevents bus contention during card hot-swap. | Use Scenario: Interfacing automated test equipment (ATE) controller with DUT's parallel test port. IC Role / Device Role / Timing Role: Direction-controlled buffer synchronizing stimulus/response data streams during functional test sequences. Use Value: Sub-10 ns propagation delay enables precise timing alignment; OE gating allows dynamic bus release between test vectors. |
| Legacy System Memory Expansion | Microcontroller Peripheral Bridge |
Use Scenario: Adding external SRAM or EPROM to 8-bit microcontrollers with limited address/data pins. IC Role / Device Role / Timing Role: Bus transceiver extending multiplexed AD bus to off-chip memory while preserving timing margins. Use Value: ALS speed and TTL compatibility ensure setup/hold timing compliance with 8051 or Z80 derivatives operating at 6–12 MHz. | Use Scenario: Connecting an ARM Cortex-M0+ GPIO bank to legacy parallel peripherals (e.g., LCD controllers, ADCs). IC Role / Device Role / Timing Role: Level-shifting and direction-managed interface between 3.3 V MCU and 5 V peripheral logic. Use Value: 5 V tolerant I/O ports accept 5 V signals safely; DIR/OE pins controlled via GPIO enable software-configurable data flow. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS645AN | IOL = 24 mA (standard version); lacks -1 suffix enhancement. | Suitable where 24 mA drive suffices; lower power consumption in static-bus scenarios. | Select SN74ALS645AN if system load capacitance and trace length do not require 48 mA sink capability. |
| SN74AS645N | AS family: faster tPLH/tPHL (≤9.5 ns), higher IOL (64 mA), but increased ICC (95 mA typical). | Better for ultra-high-speed backplanes (>20 MHz), but requires tighter thermal management. | Choose SN74AS645N only when propagation delay <10 ns is mandatory and power budget allows >2× ICC increase. |
Compared with SN74ALS645AN and SN74AS645N, the SN74ALS645A-1N uniquely balances enhanced 48 mA drive, ALS power efficiency, and proven 0–70°C reliability-making it optimal for cost-sensitive, thermally constrained industrial interfaces where moderate speed and robust drive are prioritized.
Availability
SN74ALS645A-1N is available at Aetrix Electronics and suitable for industrial backplane interfaces, test equipment coupling, legacy memory expansion, and microcontroller peripheral bridging requiring stable component supply across long-lifecycle programs.
Supply support for SN74ALS645A-1N 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 SN74ALS645A-1N belongs to TI's legacy 74ALS logic family, engineered for high-reliability, TTL-compatible bus interfacing in commercial-temperature industrial control and instrumentation systems.
FAQ
What is the maximum sink current supported by SN74ALS645A-1N?
The SN74ALS645A-1N supports a maximum low-level output current (IOL) of 48 mA per pin when VCC is maintained between 4.75 V and 5.25 V. This value is specific to the "-1" version and exceeds the 24 mA rating of the standard SN74ALS645AN. Exceeding this limit risks output stage degradation or thermal shutdown in sustained operation.
Does SN74ALS645A-1N support 3.3 V logic inputs?
No, SN74ALS645A-1N is a 5 V TTL-family device with VIH = 2.0 V minimum and VIL = 0.8 V maximum. While it may tolerate 3.3 V CMOS outputs as high-level inputs, it does not guarantee reliable switching below 2.0 V and is not 3.3 V–compatible. For mixed-voltage systems, level-shifting circuitry is required before connecting 3.3 V sources to SN74ALS645A-1N inputs.
Can SN74ALS645A-1N replace SN74ALS645AN in existing designs?
Yes, SN74ALS645A-1N is pin-compatible and functionally identical to SN74ALS645AN except for its higher 48 mA IOL rating. No PCB changes are needed, but verify that the increased output drive does not cause overshoot or ground bounce in your specific layout-especially with long traces or heavy capacitive loads.
What is the operating temperature range of SN74ALS645A-1N?
The SN74ALS645A-1N is characterized for operation from 0°C to 70°C, consistent with commercial-grade specifications. It is not rated for extended temperature ranges like the military-grade SN54ALS645A (–55°C to 125°C). Use only within this range to ensure guaranteed timing, drive, and reliability performance.
Is SN74ALS645A-1N RoHS compliant?
Yes, SN74ALS645A-1N is RoHS compliant, with lead finish specified as NiPdAu (NIPDAU) and no lead (Pb)-based solder in its construction. The part marking "SN74ALS645A-1N" appears on the package body, and full compliance documentation is available through Texas Instruments' official product page and material declarations.
SN74ALS645A-1N 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
SN74ALS645A-1N FAQ
1.How can I place an order for SN74ALS645A-1N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS645A-1N 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 SN74ALS645A-1N reliable?
The price and inventory of SN74ALS645A-1N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS645A-1N is usually 5 days.
3.What payment methods are accepted for SN74ALS645A-1N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS645A-1N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS645A-1N?
SN74ALS645A-1N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS645A-1N 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 SN74ALS645A-1N?
For technical support, including SN74ALS645A-1N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS645A-1N requirements.
6.How does Aetrix verify that SN74ALS645A-1N is sourced from the original manufacturer or authorized distributors?
All SN74ALS645A-1N 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 SN74ALS645A-1N meets industry standards.
7.What is the process for return or replacement of SN74ALS645A-1N?
All SN74ALS645A-1N units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS645A-1N, 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 SN74ALS645A-1N part is unused and in its original packaging.
Return procedure for SN74ALS645A-1N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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