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Texas Instruments SN74ALS1645ANSR
- Part No.:
- SN74ALS1645ANSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS1645ANSR.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,765
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Product details
Overview
SN74ALS1645ANSR from Texas Instruments is a noninverting octal bus transceiver with 3-state outputs in a 20-pin SOIC (DW) package, operating at 4.5–5.5 V, supporting bidirectional data flow between A and B buses with DIR-controlled direction and OE-enabled isolation. It delivers 16 mA sink and –15 mA source output drive, with propagation delays as low as 2 ns (tPHL), and is rated for 0°C to 70°C operation in industrial bus interface applications.
For engineers reviewing the SN74ALS1645ANSR datasheet, SN74ALS1645ANSR pinout, SN74ALS1645ANSR application, or SN74ALS1645ANSR equivalent, key selection criteria include its noninverting logic architecture, 3-state bus isolation timing (tPZH/tPLZ ≤ 25 ns), output drive capability under ALS family voltage thresholds, and compatibility with legacy 5-V TTL/LS bus systems requiring direction-controlled data coupling.
Technical Context
The SN74ALS1645ANSR implements asynchronous bidirectional bus communication using two independent control inputs: DIR selects data path direction (A→B or B→A), while OE enables or disables all outputs into high-impedance state. Its noninverting logic ensures signal polarity preservation across both directions.
Designed as a lower-power replacement for SN74ALS645A, it operates within the ALS family's 4.5–5.5 V supply range and meets standard TTL input thresholds (VIH = 2 V, VIL = 0.8 V), with output voltage levels VOH ≥ 2.4 V (IOH = –3 mA) and VOL ≤ 0.4 V (IOL = 8 mA).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Type | Noninverting - preserves signal polarity during bidirectional transfer between A and B buses. |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5-V TTL/LS bus systems without level-shifting. |
| Output Drive | –15 mA (source), 16 mA (sink) - sufficient to drive multiple TTL loads or terminate stubs on medium-length buses. |
| Propagation Delay | tPLH/tPHL ≤ 13 ns - supports bus clock rates up to ~30 MHz in point-to-point or lightly loaded configurations. |
| 3-State Enable Time | tPZH ≤ 12 ns, tPZL ≤ 18 ns - ensures fast bus release and minimizes contention windows during direction switching. |
| Operating Temperature | 0°C to 70°C - qualified for commercial and industrial ambient environments without derating. |
| Input Thresholds | VIH = 2 V, VIL = 0.8 V - matches standard TTL logic families for direct interfacing without translation. |
Pinout & Package
SN74ALS1645ANSR uses a 20-pin SOIC (DW) package with 0.300-inch body width and standard gull-wing lead form. Pin spacing is 0.050 inch (1.27 mm), and the package is RoHS-compliant with NiPdAu lead finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | High = A→B data transfer; Low = B→A transfer - determines real-time bus flow direction. |
| 2 (A1) | A-Bus Data Input/Output | Bi-directional I/O port connected to A-side data bus; driven by B bus when DIR = L and OE = L. |
| 3–9 (A2–A8) | A-Bus Data I/Os | Seven additional bidirectional A-side ports, identical in function to A1. |
| 10 (GND) | Ground Reference | Primary power return path for all internal logic and I/O circuits. |
| 11–18 (B1–B8) | B-Bus Data I/Os | Eight bidirectional ports for B-side bus connection; mirror A-side behavior under DIR control. |
| 19 (OE) | Output Enable Input | Low = outputs active; High = all A/B ports enter high-impedance state - enables bus isolation. |
| 20 (VCC) | Power Supply | +4.5 V to +5.5 V supply for ALS logic core and output drivers. |
Key Features
| Feature | Design Value |
|---|---|
| Noninverting Bidirectional Logic | Preserves signal polarity in both A→B and B→A modes - eliminates need for external inversion in symmetric bus architectures. |
| 3-State Output Isolation | OE-controlled high-impedance mode prevents bus contention during multi-master arbitration or power sequencing. |
| ALS Family Compatibility | Meets TTL input thresholds and output drive specs - interoperable with SN74ALS645A, SN74ALS245, and other ALS transceivers. |
| Low-Power Operation | ICC = 25–38 mA at VCC = 5.5 V - reduces thermal load vs. earlier LS/ALS transceivers in dense bus backplanes. |
| Industrial Temperature Range | Rated for 0°C to 70°C operation - suitable for embedded controllers, instrumentation, and factory automation equipment. |
Applications
| Microprocessor Bus Interface | Memory Expansion Subsystem |
|---|---|
|
Use Scenario: Connecting an 8-bit microprocessor data bus to peripheral ICs with mismatched timing or voltage domains. IC Role / Device Role / Timing Role: Bidirectional data coupler enabling synchronous read/write cycles between CPU and peripherals via DIR-synchronized handshaking. Use Value: Eliminates need for separate unidirectional buffers and simplifies PCB routing with single 20-pin SOIC footprint. |
Use Scenario: Extending address/data bus width between main controller and SRAM/ROM modules in legacy embedded systems. IC Role / Device Role / Timing Role: Direction-controlled bus repeater that isolates memory subsystem during DMA transfers or reset sequences. Use Value: Enables hot-swappable memory banks via OE-driven isolation without disrupting CPU bus activity. |
| Industrial PLC Backplane | Legacy Test Equipment Interface |
|
Use Scenario: Interfacing modular I/O cards to central controller bus in programmable logic controllers. IC Role / Device Role / Timing Role: Isolated bus transceiver managing data flow between controller and field I/O modules under DIR-selectable polling schemes. Use Value: Supports deterministic scan-cycle timing with sub-15 ns propagation delay and guaranteed 3-state disable timing. |
Use Scenario: Adapting GPIB or IEEE-488 bus signals to internal TTL-level logic in automated test equipment. IC Role / Device Role / Timing Role: Level-translating bus coupler converting instrument bus signals to processor-accessible data lanes. Use Value: Maintains signal integrity across long backplane traces using ALS-family noise margins and controlled slew rate. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS245N | Octal noninverting transceiver with separate A→B and B→A enable pins (no DIR input); requires dual OE control logic. | Suitable for fixed-direction or independently gated bus segments; less flexible for dynamic direction switching. | Select when direction is static per bus segment and discrete enable control is preferred over shared DIR. |
| SN74LS245N | Higher ICC (40–55 mA), slower tPLH/tPHL (max 25 ns), and lower VOH (2.7 V @ –15 mA) - LS-family performance trade-offs. | Compatible with older LS-based designs but consumes more power and exhibits higher propagation latency. | Choose only for drop-in replacement in existing LS designs where ALS speed/power benefits are not required. |
Compared with SN74ALS245N and SN74LS245N, the SN74ALS1645ANSR provides integrated direction control in a single pin, lower power consumption than LS variants, and faster switching - making it optimal for dynamically reconfigurable 5-V bus systems where pin count and timing predictability are critical.
Availability
SN74ALS1645ANSR is available at Aetrix Electronics and suitable for microprocessor bus interfaces, memory expansion subsystems, and industrial PLC backplanes requiring stable component supply, long-lifecycle support, and RoHS-compliant SOIC packaging.
Supply support for SN74ALS1645ANSR 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 SN74ALS1645ANSR belongs to TI's legacy ALS logic product line, engineered for high-speed, low-power 5-V TTL-compatible bus interfacing in industrial control and computing infrastructure.
FAQ
What is the logic configuration of the SN74ALS1645ANSR?
The SN74ALS1645ANSR is a noninverting octal bus transceiver: data transferred from A to B or B to A retains its original logic polarity. This differs from the inverting SN74ALS1640A and simplifies integration in systems where signal inversion would require additional logic gates or software compensation. The SN74ALS1645ANSR achieves this using ALS-family transistor-level design optimized for 5-V operation.
Does the SN74ALS1645ANSR support 3.3-V operation?
No, the SN74ALS1645ANSR is specified only for 4.5 V to 5.5 V supply operation and does not guarantee functionality or reliability below 4.5 V. Its input thresholds (VIH = 2 V, VIL = 0.8 V) and output drive characteristics are calibrated for 5-V TTL/ALS compatibility. Using the SN74ALS1645ANSR with 3.3-V logic requires level-shifting circuitry to avoid undefined states or excessive current draw.
How does the DIR pin control data flow in the SN74ALS1645ANSR?
The DIR pin on the SN74ALS1645ANSR determines real-time bus direction: when DIR = Low, data flows from B bus to A bus; when DIR = High, data flows from A bus to B bus. This single-pin control replaces dual-enable schemes used in alternatives like SN74ALS245N, reducing control logic complexity and PCB routing overhead in dynamically switched bus topologies.
What is the maximum capacitive load the SN74ALS1645ANSR can drive?
The SN74ALS1645ANSR is characterized for CL = 50 pF in switching tests, with propagation delays measured under that condition. While not explicitly rated for higher loads, its 16 mA sink and –15 mA source capability supports moderate bus stubs and typical PCB trace capacitance. For loads exceeding 50 pF, designers should verify timing margins using the device's tPLH/tPHL max values (13 ns) and account for added RC delay in system-level timing analysis.
Is the SN74ALS1645ANSR pin-compatible with SN74ALS1645AN (PDIP)?
Yes, the SN74ALS1645ANSR (SOIC-DW) and SN74ALS1645AN (PDIP-N) share identical pin numbering, signal mapping, and electrical specifications - differing only in package type and thermal characteristics. This allows direct footprint substitution in designs transitioning from through-hole to surface-mount assembly, provided board layout accommodates SOIC pad dimensions and reflow profile requirements.
SN74ALS1645ANSR 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:
- 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, 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
SN74ALS1645ANSR FAQ
1.How can I place an order for SN74ALS1645ANSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS1645ANSR 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 SN74ALS1645ANSR reliable?
The price and inventory of SN74ALS1645ANSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS1645ANSR is usually 5 days.
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Once your SN74ALS1645ANSR 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 SN74ALS1645ANSR?
For technical support, including SN74ALS1645ANSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS1645ANSR requirements.
6.How does Aetrix verify that SN74ALS1645ANSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS1645ANSR 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 SN74ALS1645ANSR meets industry standards.
7.What is the process for return or replacement of SN74ALS1645ANSR?
All SN74ALS1645ANSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS1645ANSR, 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 SN74ALS1645ANSR part is unused and in its original packaging.
Return procedure for SN74ALS1645ANSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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