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Texas Instruments SN74ALS245A-1NG4
- Part No.:
- SN74ALS245A-1NG4
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS245A-1NG4.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,284
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Product details
Overview
SN74ALS245A-1NG4 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 a maximum propagation delay of 5.5 ns at 5 V, supports ±48 mA low-level output drive (–1 version), and features pnp input structure to reduce DC loading. It is used in legacy industrial control backplanes and microprocessor system expansion interfaces.
For engineers reviewing the SN74ALS245A-1NG4 datasheet, SN74ALS245A-1NG4 pinout, SN74ALS245A-1NG4 application, or SN74ALS245A-1NG4 equivalent, key selection criteria include its 20-pin PDIP package, direction-control (DIR) and output-enable (OE) logic interface, guaranteed 3-state isolation timing, and compatibility with ALS logic family voltage thresholds and drive strength.
Technical Context
The SN74ALS245A-1NG4 implements dual-directional 8-bit data routing via a single DIR input that selects A→B (high) or B→A (low) flow, while OE independently enables or disables all outputs into high-impedance state. Its pnp-based inputs lower input current draw versus standard TTL, improving fan-out capability in dense bus environments.
Propagation delays are specified under CL = 50 pF, R1/R2 = 500 Ω, and cover both data path (tPLH/tPHL ≤ 10 ns) and 3-state enable/disable transitions (tPZH/tPLZ ≤ 20 ns). The –1 suffix denotes enhanced IOL rating (48 mA vs. 24 mA standard), validated only at VCC = 4.75–5.25 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures interoperability with standard 5-V TTL and ALS logic rails. |
| Max Propagation Delay | 5.5 ns at 5 V - Enables reliable operation in high-speed 8-bit parallel data paths up to ~180 MHz toggle rate. |
| IOL (–1 version) | 48 mA - Supports direct driving of heavily loaded buses without external buffers in industrial backplane designs. |
| VIH / VIL | 2.0 V / 0.8 V - Matches ALS family input thresholds, ensuring noise-immune switching with TTL-compatible signal sources. |
| tPZH / tPLZ | ≤ 20 ns - Guarantees fast 3-state disable/enable for dynamic bus sharing in multiprocessor or DMA-controlled systems. |
| Package | PDIP-20 - Through-hole mounting compatible with legacy PCB assembly and prototyping workflows. |
Pinout & Package
SN74ALS245A-1NG4 is supplied in a 20-pin plastic dual in-line package (PDIP), 0.300-inch body width, with standard through-hole lead spacing and JEDEC MO-091 compliance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | High = A-to-B data transfer; Low = B-to-A transfer; TTL-compatible threshold. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines connected to one bus segment; internally buffered with pnp inputs. |
| 10 (GND) | Ground Reference | Primary power return path; must be low-impedance for stable 3-state output transitions. |
| 11 (VCC) | Supply Voltage | +5 V nominal supply; decoupling capacitor required within 1 cm for noise suppression. |
| 12 (OE) | Output Enable Input | Low = outputs active; High = all outputs in high-impedance state; enables bus isolation. |
| 13–20 (B1–B8) | Port B I/O Terminals | Bidirectional data lines connected to second bus segment; electrically identical to A-side terminals. |
Key Features
| Feature | Design Value |
|---|---|
| Octal bidirectional data path | Enables full 8-bit parallel communication between two independent buses using single DIR control line. |
| 3-state outputs with fast enable/disable | tPZH/tPLZ ≤ 20 ns ensures minimal bus contention during arbitration in shared-memory systems. |
| pnp input structure | Reduces input current to ≤0.1 mA, increasing fan-out capacity and lowering power supply loading on driving devices. |
| –1 version enhanced drive | 48 mA IOL rating allows direct interfacing with legacy 50-Ω terminated buses or multiple TTL loads without buffering. |
| TTL-compatible voltage thresholds | VIH = 2.0 V and VIL = 0.8 V ensure robust noise margin and interoperability with 74LS/74ALS/74F families. |
Applications
| Industrial Backplane Interface | Microprocessor System Expansion |
|---|---|
Use Scenario: Interfacing multiple PLC I/O modules to a central controller bus in factory automation cabinets. IC Role / Device Role / Timing Role: Bidirectional data transceiver isolating and routing 8-bit status/control words between isolated bus segments. Use Value: 48 mA drive strength ensures reliable signal integrity across 30-cm ribbon cable runs with multiple stubs. | Use Scenario: Adding peripheral memory or I/O cards to an 8086/8088-based embedded controller. IC Role / Device Role / Timing Role: Bus transceiver enabling CPU address/data bus extension while maintaining timing compliance per Intel 8288 requirements. Use Value: 5.5 ns max tpd meets sub-100 ns bus cycle timing budgets for 5-MHz CPU operation. |
| Legacy Test Equipment Data Link | Avionics Maintenance Interface |
Use Scenario: Connecting digital pattern generators and logic analyzers to DUT test fixtures via shared 8-bit parallel bus. IC Role / Device Role / Timing Role: Direction-controlled buffer providing clean signal coupling and isolation between instrument and device-under-test. Use Value: Fast 3-state disable (tPLZ ≤ 15 ns) prevents bus conflicts during instrument reconfiguration sequences. | Use Scenario: Enabling ground-based diagnostic tools to read/write configuration registers in airborne flight control units. IC Role / Device Role / Timing Role: Isolation transceiver supporting MIL-STD-1553B auxiliary data channel bridging in maintenance ports. Use Value: Guaranteed operation over 0°C to 70°C and RoHS-compliant N-package support long-term field deployment reliability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS245AN | Standard version with 24 mA IOL (vs. 48 mA for –1); otherwise identical pinout, timing, and logic behavior. | Suitable where bus loading is light (< 10 TTL loads) and cost sensitivity outweighs drive margin. | Select SN74ALS245AN only if verified load current remains ≤24 mA; SN74ALS245A-1NG4 preferred for industrial backplanes. |
| SN74AS245N | Faster propagation (7.5 ns max), higher ICC (95 mA), and AS-family input thresholds (VIL = 0.8 V, VIH = 2.0 V same, but different internal structure). | Used in high-speed instrumentation where timing margin is critical, but requires tighter power delivery and layout due to higher di/dt. | Choose SN74AS245N only when sub-8 ns delay is mandatory and board-level noise control is implemented. |
Compared with SN74ALS245AN and SN74AS245N, SN74ALS245A-1NG4 uniquely balances robust 48 mA drive, proven ALS noise immunity, and PDIP manufacturability-making it optimal for retrofitting and sustaining legacy 5-V TTL systems where reliability and compatibility outweigh raw speed.
Availability
SN74ALS245A-1NG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, microprocessor system expansion, legacy test equipment data links, and avionics maintenance interfaces requiring stable component supply across extended product lifecycles.
Supply support for SN74ALS245A-1NG4 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 company founded in 1930, specializing in analog, embedded processing, and logic ICs for industrial, automotive, and communications markets.
The SN74ALS245A-1NG4 belongs to TI's legacy 74ALS logic family, engineered for high noise immunity, low power consumption, and compatibility with existing TTL infrastructure in long-lifecycle industrial and defense systems.
FAQ
What is the function of the DIR pin on the SN74ALS245A-1NG4?
The DIR (direction) pin on the SN74ALS245A-1NG4 controls data flow direction between the A and B bus ports. When DIR is high, data transfers from A to B; when DIR is low, data flows from B to A. This single-pin control eliminates the need for separate transmit/receive buffers in bidirectional parallel interfaces, simplifying PCB layout and reducing component count in systems like industrial backplanes and microprocessor expansions using the SN74ALS245A-1NG4.
How does the "–1" suffix affect the electrical specifications of SN74ALS245A-1NG4?
The "–1" suffix on SN74ALS245A-1NG4 specifies an enhanced low-level output current rating of 48 mA (versus 24 mA for the standard SN74ALS245A), validated only when VCC is maintained between 4.75 V and 5.25 V. All other parameters-including propagation delay, input thresholds, and 3-state timing-remain identical to the base part. This makes SN74ALS245A-1NG4 ideal for driving heavily loaded buses where standard ALS drive strength is insufficient.
Can SN74ALS245A-1NG4 be used in place of SN74ALS245AN in an existing design?
Yes, SN74ALS245A-1NG4 is pin-compatible and functionally identical to SN74ALS245AN, with the exception of its higher 48 mA IOL rating. No PCB changes are required, and it operates within the same 4.5–5.5 V VCC range and 0°C to 70°C temperature grade. Substituting SN74ALS245A-1NG4 provides additional drive margin for aging or marginally loaded systems, making it a drop-in upgrade for legacy designs originally specifying SN74ALS245AN.
What is the recommended decoupling strategy for SN74ALS245A-1NG4?
TI recommends a 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 11) and GND (pin 10) pins of the SN74ALS245A-1NG4, with trace length under 1 cm. For systems with multiple SN74ALS245A-1NG4 devices or high-frequency switching, add a bulk 4.7 µF–10 µF tantalum or aluminum electrolytic capacitor near the power entry point. This ensures stable 3-state transitions and minimizes ground bounce during simultaneous output switching in the SN74ALS245A-1NG4.
Does SN74ALS245A-1NG4 support hot-swap or live-insertion into a powered bus?
No, SN74ALS245A-1NG4 is not designed for hot-swap operation. Its absolute maximum ratings do not include live insertion stress conditions, and the device lacks bus-fault protection or power-up sequencing logic. Applying VCC before establishing proper GND connection-or enabling OE while bus voltages are floating-may cause latch-up or parametric shift. Always power-cycle the entire system before inserting or removing SN74ALS245A-1NG4 in operational environments.
SN74ALS245A-1NG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- 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
SN74ALS245A-1NG4 FAQ
1.How can I place an order for SN74ALS245A-1NG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS245A-1NG4 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-1NG4 reliable?
The price and inventory of SN74ALS245A-1NG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS245A-1NG4 is usually 5 days.
3.What payment methods are accepted for SN74ALS245A-1NG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS245A-1NG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS245A-1NG4?
SN74ALS245A-1NG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS245A-1NG4 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-1NG4?
For technical support, including SN74ALS245A-1NG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS245A-1NG4 requirements.
6.How does Aetrix verify that SN74ALS245A-1NG4 is sourced from the original manufacturer or authorized distributors?
All SN74ALS245A-1NG4 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-1NG4 meets industry standards.
7.What is the process for return or replacement of SN74ALS245A-1NG4?
All SN74ALS245A-1NG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS245A-1NG4, 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-1NG4 part is unused and in its original packaging.
Return procedure for SN74ALS245A-1NG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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