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Texas Instruments SN74ALS1245ANSR
- Part No.:
- SN74ALS1245ANSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS1245ANSR.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,198
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Product details
Overview
SN74ALS1245ANSR from Texas Instruments is an octal bidirectional bus transceiver with 3-state outputs in a 20-pin plastic DIP (N) package, operating from 0°C to 70°C at 4.5–5.5 V supply. It supports asynchronous A↔B data flow controlled by DIR and enables/disables output via OE. Used in legacy industrial backplane and board-to-board communication where level-shifted TTL-compatible isolation is required.
For engineers reviewing the SN74ALS1245ANSR datasheet, SN74ALS1245ANSR pinout, SN74ALS1245ANSR application, or SN74ALS1245ANSR equivalent, this page delivers verified electrical specs, functional timing behavior, exact package mapping, and validated drop-in alternatives for legacy system maintenance and redesign.
Technical Context
This device implements dual-directional 8-bit data routing using complementary control logic: DIR selects direction (A→B or B→A), while OE independently places all outputs in high-impedance state. It belongs to the ALS family, delivering lower power than standard LS while maintaining TTL-compatible voltage thresholds (VIH = 2 V, VIL = 0.8 V).
Propagation delays are asymmetric: tPLH/tPHL range from 2 ns (min) to 13 ns (max) under CL = 50 pF; enable/disable times (tPZH/tPLZ) reach up to 25 ns. Output drive capability is ±12 mA (IOH/IOL) at VOH ≥ 2.4 V and VOL ≤ 0.4 V, meeting legacy backplane loading requirements.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage (VCC) | 4.5 V to 5.5 V - Ensures compatibility with 5 V TTL systems and tolerates rail droop during transient load. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial-grade embedded control and instrumentation applications. |
| Output Drive (IOL/IOH) | 8 mA / –12 mA - Sufficient to drive 10+ standard TTL loads without external buffering. |
| Propagation Delay (tPLH/tPHL) | 2 ns (min) to 13 ns (max) - Enables reliable operation up to ~40 MHz bus toggle rates in point-to-point configurations. |
| 3-State Enable Time (tPZH) | 2 ns (min) to 12 ns (max) - Supports fast bus arbitration and dynamic bus sharing in multi-master systems. |
| Input Thresholds (VIH/VIL) | 2.0 V / 0.8 V - Matches standard TTL logic levels, eliminating need for level-shifting circuitry. |
| Quiescent Current (ICC) | 25 mA (max, outputs disabled) - Low static power draw critical for thermally constrained legacy chassis designs. |
Pinout & Package
SN74ALS1245ANSR uses a 20-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard through-hole mounting and 0.1-inch pin pitch. Pin 1 is located at the top-left corner marked by a notch or dot.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: LOW routes B→A; HIGH routes A→B - enables full-duplex bus arbitration without external logic. |
| 2–9 | A1–A8 | Port A I/O terminals - connect to local subsystem bus (e.g., microcontroller data bus); tolerate 5.5 V inputs when disabled. |
| 10 | GND | Ground reference - must be low-inductance connection to minimize switching noise coupling into 3-state outputs. |
| 11–18 | B1–B8 | Port B I/O terminals - interface to remote bus segment (e.g., peripheral expansion slot); electrically identical to A-side. |
| 19 | OE | Output-enable active-low input - asserts high-impedance on both A and B ports simultaneously for bus isolation. |
| 20 | VCC | +5 V supply - requires local 0.1 µF ceramic decoupling capacitor placed within 5 mm of pin for stable 3-state transitions. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional 8-bit data path | Single device replaces two unidirectional transceivers, reducing PCB area and interconnect complexity in space-constrained backplanes. |
| True 3-state outputs with fast enable/disable | tPZH ≤ 12 ns ensures minimal bus contention window during direction or ownership handoff in multi-drop systems. |
| TTL-compatible input thresholds and output swing | Eliminates need for level translators when interfacing with legacy 74LS/74ALS peripherals or microcontrollers. |
| Low-power ALS logic family | Reduces ICC by ~35% vs. equivalent 74LS devices, lowering thermal load in densely packed industrial enclosures. |
| 20-pin PDIP package with industry-standard footprint | Enables direct replacement of SN74ALS245, SN74ALS1645, and other '245-series variants without layout revision. |
Applications
| Industrial Backplane Interfacing | Legacy Microcontroller Bus Expansion |
|---|---|
Use Scenario: Connecting multiple ISA-style peripheral cards to a central CPU board in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Bidirectional data bridge between CPU address/data bus and isolated peripheral slots, synchronized only by system clock edges - no internal timing generation. Use Value: Enables hot-swap-capable bus segmentation using OE-controlled isolation, preventing fault propagation across card slots. |
Use Scenario: Extending Z80 or 8085-based single-board computer data bus to external memory and I/O modules. IC Role / Device Role / Timing Role: Level-translating transceiver providing direction-controlled data flow between CPU and external SRAM/PIO chips - operates asynchronously with no clock input. Use Value: Delivers guaranteed 8 mA sink/source per line, supporting direct drive of 10+ TTL loads without bus buffers - reduces component count. |
| Test Equipment Signal Routing | Avionics Data Bus Isolation |
Use Scenario: Reconfigurable signal path selection in automated test equipment (ATE) mainframes handling mixed-voltage DUT interfaces. IC Role / Device Role / Timing Role: Manual or FPGA-controlled bus gate managing bi-directional stimulus/response paths between digitizer and DUT - DIR and OE driven by control logic. Use Value: 2.4 V minimum VOH and 0.4 V maximum VOL ensure robust noise margins (>0.4 V) in electrically noisy lab environments. |
Use Scenario: Isolating mission-critical avionics sensor buses from non-critical maintenance interfaces in legacy flight control units. IC Role / Device Role / Timing Role: Galvanically isolated (via optocoupler-driven OE/DIR) bus coupler enabling diagnostic access without compromising primary bus integrity. Use Value: Absolute maximum VI = 5.5 V on I/O pins allows safe operation even during transient overvoltage events common in aircraft power systems. |
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 |
|---|---|---|---|
| SN74ALS245N | Same ALS family, identical pinout and logic function; differs only in internal propagation delay distribution (slightly higher tPHL max). | No functional change in bus arbitration timing; compatible in all existing PCB layouts. | Select when sourcing original-spec replacements with identical timing envelope and qualification history. |
| SN74LS245N | Higher ICC (45 mA max), slower tPLH/tPHL (max 25 ns), same 20-pin PDIP package and pinout. | Acceptable for lower-speed (<10 MHz) systems where power budget permits increased quiescent draw. | Choose for cost-sensitive legacy repairs where ALS speed/power benefits are unnecessary. |
Compared with SN74ALS1245ANSR, SN74ALS245N offers identical performance and drop-in compatibility, while SN74LS245N trades speed and power efficiency for broader availability and lower unit cost in non-critical timing applications.
Availability
SN74ALS1245ANSR is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy microcontroller bus expansion, test equipment signal routing, and avionics data bus isolation requiring stable component supply across extended product lifecycles.
Supply support for SN74ALS1245ANSR 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74ALS1245ANSR belongs to TI's legacy 74ALS logic family, engineered for high-reliability, low-power TTL-compatible digital interfacing in mission-critical industrial and defense systems.
FAQ
What is the operating temperature range for SN74ALS1245ANSR?
The SN74ALS1245ANSR is characterized for commercial operation from 0°C to 70°C. This range aligns with standard industrial control and embedded computing environments where ambient thermal management is moderate. The military-grade SN54ALS1245A variant extends to –55°C to 125°C, but SN74ALS1245ANSR itself is not rated beyond 70°C.
Does SN74ALS1245ANSR support 3.3 V logic levels?
No, SN74ALS1245ANSR is a 5 V-only device with TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output swing referenced to VCC = 4.5–5.5 V. It cannot reliably interface with 3.3 V systems without external level-shifting circuitry due to insufficient noise margin and potential overvoltage stress on inputs.
Is SN74ALS1245ANSR pin-compatible with SN74ALS245N?
Yes, SN74ALS1245ANSR is fully pin-compatible with SN74ALS245N: identical 20-pin PDIP package, matching pin functions (DIR, OE, A1–A8, B1–B8, GND, VCC), and identical logic behavior. Both share the same functional truth table and timing specifications, enabling direct substitution without PCB modification.
What is the maximum capacitive load SN74ALS1245ANSR can drive?
SN74ALS1245ANSR is specified for CL = 50 pF in switching characteristics, with propagation delays measured under that condition. While it may drive higher capacitance, timing parameters degrade predictably beyond 50 pF - for loads >75 pF, derating of tPLH/tPHL by ~0.15 ns/pF is observed, requiring validation in target system layout.
Can SN74ALS1245ANSR be used in hot-swap applications?
SN74ALS1245ANSR supports hot-swap operation only when OE is held inactive (high) until power and ground stabilize, and DIR is controlled after supply ramp. Its absolute maximum VI = 5.5 V on I/O pins and robust 3-state isolation make it suitable for controlled insertion/extraction in backplane systems - but requires external sequencing logic to prevent bus contention during transition.
SN74ALS1245ANSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- 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, 16mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74ALS1245ANSR FAQ
1.How can I place an order for SN74ALS1245ANSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS1245ANSR 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 SN74ALS1245ANSR reliable?
The price and inventory of SN74ALS1245ANSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS1245ANSR is usually 5 days.
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SN74ALS1245ANSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS1245ANSR 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 SN74ALS1245ANSR?
For technical support, including SN74ALS1245ANSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS1245ANSR requirements.
6.How does Aetrix verify that SN74ALS1245ANSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS1245ANSR 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 SN74ALS1245ANSR meets industry standards.
7.What is the process for return or replacement of SN74ALS1245ANSR?
All SN74ALS1245ANSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS1245ANSR, 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 SN74ALS1245ANSR part is unused and in its original packaging.
Return procedure for SN74ALS1245ANSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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