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Texas Instruments SN74ALS245A-1DW
- Part No.:
- SN74ALS245A-1DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS245A-1DW.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:247
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Product details
Overview
SN74ALS245A-1DW 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 5.5 ns max propagation delay at 5 V, supports 48 mA low-level output current (IOL), and features pnp inputs to reduce DC loading. It is used in industrial backplane interfaces and legacy system bus isolation.
For engineers reviewing the SN74ALS245A-1DW datasheet, SN74ALS245A-1DW pinout, SN74ALS245A-1DW application, or SN74ALS245A-1DW equivalent, key selection criteria include its -1 version's enhanced 48 mA sink capability, SOIC-20 package thermal resistance (58°C/W), 3-state control timing (tPZH/tPLZ ≤ 20 ns), and compatibility with 5-V TTL logic families in bus arbitration and level-shifting roles.
Technical Context
The SN74ALS245A-1DW implements dual-directional bus communication via DIR input to select A→B or B→A data flow, while OE enables/disables all outputs into high-impedance state. Its pnp input structure minimizes input current draw, reducing loading on upstream drivers.
It uses bipolar ALS (Advanced Low-Power Schottky) technology, delivering improved speed-power trade-off over standard LS logic: 5.5 ns tpd vs. typical 9–10 ns for SN74LS245, with ICC disabled ≤ 58 mA and IOL rated to 48 mA under 4.75–5.25 V - a defining feature of the "-1" variant.
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 without functional loss. |
| Max Propagation Delay | 5.5 ns at VCC = 5 V - enables reliable operation in high-speed 20+ MHz bus environments with tight timing margins. |
| IOL (Low-Level Output) | 48 mA (–1 version only, VCC = 4.75–5.25 V) - supports driving heavier capacitive loads or multiple TTL inputs without external buffers. |
| 3-State Enable/Disable Time | tPZH/tPLZ ≤ 20 ns - guarantees fast bus release for time-critical arbitration and avoids bus contention during state transitions. |
| Input Structure | pnp inputs - reduces DC input current to ≤ 0.1 mA, lowering driver loading and improving fan-out in cascaded bus topologies. |
| θJA Thermal Resistance | 58°C/W (SOIC-DW) - defines maximum junction temperature rise under continuous operation; critical for thermal design in enclosed industrial enclosures. |
Pinout & Package
SN74ALS245A-1DW is housed in a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body, 2.65 mm max height, with 1.27 mm lead pitch and gull-wing leads. Pin 1 is located at the top-left corner with index marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Determines data flow direction: logic low = B-to-A, logic high = A-to-B; referenced to GND/VCC, not differential. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines connected to one bus segment; internally buffered with pnp inputs and totem-pole outputs. |
| 10 (GND) | Ground Reference | Primary signal return path; must be low-impedance to maintain noise margin and switching integrity. |
| 11–18 (B1–B8) | Port B I/O Terminals | Bidirectional data lines connected to second bus segment; electrically identical to A-side terminals. |
| 19 (VCC) | Supply Voltage | 5-V nominal power rail; decoupling capacitor (0.1 µF ceramic) required within 10 mm of this pin for stable switching. |
| 20 (OE) | Output Enable Input | Active-low control: logic low enables transceiver; logic high places all A/B outputs in high-impedance state for bus isolation. |
Key Features
| Feature | Design Value |
|---|---|
| Enhanced Sink Current | 48 mA IOL (–1 version) enables direct drive of up to 12 standard TTL loads without buffering, reducing component count in bus interface designs. |
| Low Propagation Delay | 5.5 ns max tpd at 5 V allows integration into 15–20 MHz synchronous bus systems where cycle time budgets are ≤ 50 ns. |
| pnp Input Architecture | Reduces input current to ≤ 0.1 mA per control pin, minimizing loading on microcontroller GPIOs or FPGA I/O banks driving DIR/OE. |
| 3-State Bus Isolation | Simultaneous high-Z disable of all 16 I/Os via OE eliminates bus contention during master handoff or fault recovery sequences. |
Applications
| Industrial Backplane Interface | Legacy System Bus Arbitration |
|---|---|
Use Scenario: Isolating CPU and peripheral modules on a 20-slot VMEbus-compatible backplane operating at 16 MHz. IC Role / Device Role / Timing Role: Bidirectional data transceiver managing address/data multiplexing between master and slave slots under DIR-controlled flow and OE-gated arbitration. Use Value: 48 mA IOL drives 50 pF trace capacitance + 8 TTL inputs per line without timing violation; 5.5 ns tpd meets VMEbus Tds < 12 ns requirement. | Use Scenario: Enabling hot-swap capability in a modular PLC rack where modules insert/remove while main bus remains active. IC Role / Device Role / Timing Role: Bus isolator that disconnects module I/O upon insertion detection via OE, preventing transient glitches during connection. Use Value: tPLZ ≤ 15 ns ensures sub-cycle bus release; pnp inputs prevent floating-state leakage during partial insertion. |
| Microcontroller-to-Peripheral Bridge | TTL-Level Bus Translation |
Use Scenario: Interfacing an 8-bit microcontroller with external SRAM and parallel EEPROM sharing a common 8-bit data bus. IC Role / Device Role / Timing Role: Direction-controlled transceiver allowing MCU to read from or write to memory devices using shared D0–D7 lines. Use Value: DIR tied to WR# signal provides automatic direction sensing; 5.5 ns delay preserves MCU's 200 ns minimum memory access time. | Use Scenario: Level-matching between 5-V TTL logic (MCU) and older 5-V LSTTL peripherals with higher input current requirements. IC Role / Device Role / Timing Role: Current-boosting buffer ensuring compatible VIH/VIL thresholds and sufficient drive strength across mixed-logic-family bus segments. Use Value: 48 mA IOL sustains valid VOH ≥ 2.4 V when driving 10 LSTTL inputs (each drawing 1.6 mA), maintaining noise margin > 400 mV. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS245ADWR | Standard version (non-–1); IOL = 24 mA max, same SOIC-DW package and pinout. | Limited to lighter bus loads (≤ 6 TTL inputs); unsuitable where 48 mA sink is required for timing or voltage margin. | Select SN74ALS245ADWR only if system load is verified ≤ 24 mA and cost sensitivity outweighs performance headroom. |
| SN74AS245DWR | AS family: faster tpd = 7.5 ns max but higher ICC (97 mA active), same 20-pin SOIC-DW footprint. | Higher power consumption limits use in thermally constrained or battery-backed systems; superior speed benefits high-frequency bus designs. | Choose SN74AS245DWR when propagation delay is critical and thermal/power budget permits 2× higher active current. |
Compared with SN74ALS245ADWR and SN74AS245DWR, the SN74ALS245A-1DW uniquely balances enhanced drive strength (48 mA), moderate power (58 mA ICC disabled), and proven ALS reliability-making it optimal for industrial bus interfaces requiring robustness without AS-speed overhead.
Availability
SN74ALS245A-1DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus arbitration, and microcontroller-to-peripheral bridging requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS245A-1DW 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 decades of heritage in TTL and advanced logic families.
The SN74ALS245A-1DW belongs to TI's ALS (Advanced Low-Power Schottky) logic product line, engineered for industrial and military-grade reliability in 5-V bus interface applications where speed, drive strength, and thermal stability are prioritized over ultra-low power.
FAQ
What is the maximum recommended low-level output current for SN74ALS245A-1DW?
The SN74ALS245A-1DW is rated for a maximum low-level output current (IOL) of 48 mA when VCC is maintained between 4.75 V and 5.25 V. This specification applies exclusively to the "-1" variant and is confirmed in the electrical characteristics table under recommended operating conditions. Exceeding this current may cause VOL to exceed 0.5 V, violating TTL logic thresholds.
Does SN74ALS245A-1DW support bidirectional data flow without external logic?
Yes, SN74ALS245A-1DW supports fully autonomous bidirectional data flow using only the DIR input. When DIR = low, data transfers from B bus to A bus; when DIR = high, data flows from A bus to B bus. No additional control logic or sequencing is required - the internal circuitry handles direction routing transparently.
What is the thermal resistance (θJA) of SN74ALS245A-1DW in its SOIC-DW package?
The SN74ALS245A-1DW has a junction-to-ambient thermal resistance (θJA) of 58°C/W in the SOIC-DW package, as specified in the absolute maximum ratings table. This value assumes standard JEDEC test board conditions (2-layer board, 1-in² copper pad). Actual θJA in end equipment depends on PCB layout, copper area, and airflow.
Can SN74ALS245A-1DW be used in place of SN74LS245N?
SN74ALS245A-1DW is functionally and pin-compatible with SN74LS245N but offers superior performance: 5.5 ns max tpd vs. 10 ns for LS, and 48 mA IOL vs. 24 mA. However, due to higher ICC (up to 60 mA active), verify power supply capacity and thermal margin before substitution. The SOIC-DW package also differs mechanically from PDIP-N.
Is SN74ALS245A-1DW RoHS compliant?
Yes, SN74ALS245A-1DW is RoHS compliant, with NiPdAu (NIPDAU) lead finish and MSL Level-1 rating (260°C peak reflow, unlimited floor life). This is confirmed in TI's Package Option Addendum, where SN74ALS245A-1DWR.A (tape-and-reel variant) is explicitly marked "Yes" under RoHS column.
SN74ALS245A-1DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- 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:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74ALS245A-1DW FAQ
1.How can I place an order for SN74ALS245A-1DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS245A-1DW 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 SN74ALS245A-1DW reliable?
The price and inventory of SN74ALS245A-1DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS245A-1DW is usually 5 days.
3.What payment methods are accepted for SN74ALS245A-1DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS245A-1DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS245A-1DW?
SN74ALS245A-1DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS245A-1DW 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 SN74ALS245A-1DW?
For technical support, including SN74ALS245A-1DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS245A-1DW requirements.
6.How does Aetrix verify that SN74ALS245A-1DW is sourced from the original manufacturer or authorized distributors?
All SN74ALS245A-1DW 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 SN74ALS245A-1DW meets industry standards.
7.What is the process for return or replacement of SN74ALS245A-1DW?
All SN74ALS245A-1DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS245A-1DW, 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 SN74ALS245A-1DW part is unused and in its original packaging.
Return procedure for SN74ALS245A-1DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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