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Texas Instruments SN74ALS245A-1DWR
- Part No.:
- SN74ALS245A-1DWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS245A-1DWR.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,575
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Product details
Overview
SN74ALS245A-1DWR 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 48 mA low-level output current (IOL), achieves 5.5 ns max propagation delay at 5 V, and features pnp input structure to reduce DC loading. It is used in industrial backplane interfaces and legacy system bus expansion.
For engineers reviewing the SN74ALS245A-1DWR datasheet, SN74ALS245A-1DWR pinout, SN74ALS245A-1DWR application, or SN74ALS245A-1DWR equivalent, key selection criteria include its -1 version's enhanced drive capability (48 mA IOL), SOIC-DW package thermal performance (θJA = 58°C/W), 3-state control logic (DIR/OE), and compatibility with 5-V TTL signal environments.
Technical Context
The SN74ALS245A-1DWR implements dual-directional bus isolation using a single DIR input to select data flow direction (A→B or B→A) and an active-low OE input to enable/disable all outputs into high-impedance state. Its pnp-based input stage minimizes input current draw across temperature, supporting stable operation in noise-sensitive bus environments.
It conforms to ALS logic family characteristics: guaranteed VOH ≥ 2.4 V at IOL = 12 mA, VOL ≤ 0.5 V at IOL = 48 mA (VCC = 4.75–5.25 V), and tPLH/tPHL ≤ 10 ns under CL = 50 pF load. No internal latch or clocking - purely combinatorial transceiver behavior.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - supports standard 5-V TTL supply rails with ±10% tolerance. |
| Max Propagation Delay | 5.5 ns at VCC = 5 V - enables high-speed bus handshaking in legacy computing and instrumentation. |
| IOL (–1 version) | 48 mA - drives heavy capacitive loads (e.g., long traces, multiple inputs) without external buffers. |
| VOH / VOL | ≥2.4 V / ≤0.5 V - ensures robust TTL logic level compatibility and noise margin in multi-drop buses. |
| Input Structure | pnp inputs - reduces DC input current (II ≤ 0.1 mA), lowering bus loading and power dissipation. |
| Thermal Impedance | θJA = 58°C/W (DW package) - defines junction-to-ambient rise under full-output switching; critical for thermal derating in dense PCB layouts. |
Pinout & Package
SN74ALS245A-1DWR uses a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body, 1.27 mm lead pitch, 2.65 mm max height, RoHS-compliant NiPdAu lead finish, and MSL Level-1 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A1–A8 inputs/outputs | Port A bidirectional I/O - connects to source bus; direction controlled by DIR. |
| 11, 13, 14, 15, 16, 17, 18, 19 | B1–B8 inputs/outputs | Port B bidirectional I/O - connects to destination bus; direction controlled by DIR. |
| 9 | GND | Ground reference for all logic and output stages; must be low-impedance connection. |
| 10 | VCC | Positive supply (4.5–5.5 V); decoupling capacitor required near pin for transient current stability. |
| 12 | OE | Active-low output enable - asserts high-Z on both A and B ports when high; synchronizes bus isolation. |
| 20 | DIR | Direction control - low = B→A data flow, high = A→B data flow; determines signal path polarity. |
Key Features
| Feature | Design Value |
|---|---|
| Enhanced drive strength | 48 mA IOL (–1 version) enables direct driving of 50+ pF bus loads without repeaters. |
| Low DC input loading | pnp input structure limits II ≤ 0.1 mA, reducing cumulative bus capacitance and power draw. |
| Fast 3-state enable/disable | tPZH/tPLZ ≤ 20 ns ensures rapid bus arbitration and prevents contention during mode transitions. |
| TTL-compatible voltage thresholds | VIH = 2.0 V, VIL = 0.8 V - interoperates seamlessly with legacy 74LS/74F logic families. |
| Robust absolute ratings | 7 V max VCC and VI, –65°C to +150°C storage - supports industrial handling and rework conditions. |
Applications
| Industrial Backplane Interface | Legacy System Bus Expansion |
|---|---|
Use Scenario: Isolating and translating data between CPU and peripheral modules on a 20-slot Eurocard backplane. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A-bus (CPU side) ↔ B-bus (peripheral side) under DIR/OE control. Use Value: 48 mA drive supports 15 cm trace lengths with 20 pF/cm loading while maintaining <10 ns skew across all 8 lines. | Use Scenario: Adding ISA-compatible I/O cards to a retro-computing motherboard with limited drive capability. IC Role / Device Role / Timing Role: Level-shifting and buffering between motherboard data bus and card-local bus with 3-state isolation. Use Value: pnp inputs reduce total bus loading by >60% vs. standard 74LS245, preventing signal integrity collapse at 8 MHz. |
| Test Equipment Data Acquisition | Automated Manufacturing Controller |
Use Scenario: Routing sensor data from analog front-end ADCs to microcontroller via shared parallel bus. IC Role / Device Role / Timing Role: Controlled-direction transceiver enabling synchronized read/write bursts without bus contention. Use Value: 5.5 ns max tpd allows sub-100 ns sampling window alignment across 8-channel parallel acquisition. | Use Scenario: Interfacing PLC I/O modules to main controller over a deterministic parallel control bus. IC Role / Device Role / Timing Role: Isolating field-side digital inputs from controller-side logic using OE-gated 3-state outputs. Use Value: Guaranteed VOL ≤ 0.5 V at 48 mA ensures reliable low-level recognition even with 200 mV ground offset. |
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 (24 mA IOL), same SOIC-DW package and pinout. | Limited to lighter bus loads (<25 pF); unsuitable for long-trace or high-fanout scenarios. | Select when drive requirement ≤24 mA and cost sensitivity outweighs margin needs. |
| SN74AS245DWR | Faster (7 ns max tpd), higher IOL (64 mA), but increased ICC (97 mA vs. 60 mA). | Higher power consumption and EMI; requires stricter decoupling and thermal management. | Choose for timing-critical paths where propagation delay dominates over power budget. |
Compared with SN74ALS245ADWR and SN74AS245DWR, the SN74ALS245A-1DWR uniquely balances 48 mA drive, 5.5 ns speed, and 60 mA ICC - making it optimal for industrial backplanes where reliability, fanout, and thermal headroom are co-constrained.
Availability
SN74ALS245A-1DWR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus expansion, test equipment data acquisition, and automated manufacturing controllers requiring stable component supply across extended production lifecycles.
Supply support for SN74ALS245A-1DWR 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 delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74ALS245A-1DWR belongs to TI's legacy ALS logic family, engineered for high-noise-immunity, low-power 5-V TTL bus interfacing in mission-critical industrial and instrumentation systems.
FAQ
What is the maximum recommended output current for SN74ALS245A-1DWR?
The SN74ALS245A-1DWR supports up to 48 mA low-level output current (IOL) when VCC is between 4.75 V and 5.25 V. This is the defining feature of the "–1" variant and exceeds the 24 mA rating of the standard SN74ALS245A. Exceeding this limit risks parametric shift or accelerated wear under continuous operation.
Does SN74ALS245A-1DWR support 3.3-V logic levels?
No, SN74ALS245A-1DWR is strictly a 5-V TTL device with VCC range 4.5 V to 5.5 V and input thresholds (VIH = 2.0 V, VIL = 0.8 V) optimized for 5-V signaling. It lacks 3.3-V tolerant inputs or outputs and must not be directly interfaced with 3.3-V systems without level translation.
How does the DIR pin control data flow direction in SN74ALS245A-1DWR?
In SN74ALS245A-1DWR, DIR = low enables B→A data transmission (B ports drive A ports), while DIR = high enables A→B transmission (A ports drive B ports). The direction is purely combinatorial - no internal latching - and changes propagate through the transceiver within the specified tPLH/tPHL delay.
What is the thermal resistance (θJA) of the SN74ALS245A-1DWR SOIC package?
The SN74ALS245A-1DWR in SOIC-DW package has a junction-to-ambient thermal resistance (θJA) of 58°C/W, measured per JESD 51-7. This value assumes standard JEDEC 2S2P test board conditions and is essential for calculating worst-case junction temperature under full-output switching loads.
Can SN74ALS245A-1DWR replace SN74ALS245ADWR in an existing design?
Yes, SN74ALS245A-1DWR is pin-compatible and functionally identical to SN74ALS245ADWR, with the sole enhancement being higher 48 mA IOL capability. No PCB or firmware changes are needed; the upgrade improves drive margin for marginal bus loads without altering logic behavior or timing parameters.
SN74ALS245A-1DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74ALS245A-1DWR FAQ
1.How can I place an order for SN74ALS245A-1DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS245A-1DWR 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-1DWR reliable?
The price and inventory of SN74ALS245A-1DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS245A-1DWR is usually 5 days.
3.What payment methods are accepted for SN74ALS245A-1DWR?
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4.How is shipping managed for SN74ALS245A-1DWR?
SN74ALS245A-1DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS245A-1DWR 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-1DWR?
For technical support, including SN74ALS245A-1DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS245A-1DWR requirements.
6.How does Aetrix verify that SN74ALS245A-1DWR is sourced from the original manufacturer or authorized distributors?
All SN74ALS245A-1DWR 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-1DWR meets industry standards.
7.What is the process for return or replacement of SN74ALS245A-1DWR?
All SN74ALS245A-1DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS245A-1DWR, 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-1DWR part is unused and in its original packaging.
Return procedure for SN74ALS245A-1DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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