My Inquiry
My Account
Texas Instruments SN74ALS1645AN
- Part No.:
- SN74ALS1645AN
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS1645AN.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,219
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS1645AN from Texas Instruments is a noninverting octal bus transceiver with 3-state outputs in a 20-pin PDIP package, operating at 4.5–5.5 V, supporting bidirectional data flow between A and B buses with direction control (DIR) and output enable (OE), used in legacy industrial backplane and memory expansion interfaces.
For engineers reviewing the SN74ALS1645AN datasheet, SN74ALS1645AN pinout, SN74ALS1645AN application, or SN74ALS1645AN equivalent, key selection criteria include its noninverting logic, 0°C to 70°C temperature range, 13 ns max tPHL/tPLH propagation delay, 38 mA max ICC, and compatibility with ALS logic family voltage thresholds.
Technical Context
The SN74ALS1645AN implements asynchronous bidirectional bus communication using two independent 3-state output drivers per data path, controlled by DIR to select A→B or B→A direction and OE to place all outputs in high-impedance state. It uses bipolar ALS (Advanced Low-power Schottky) technology for improved speed-power trade-off over standard TTL.
Its electrical interface conforms to ALS-compatible input thresholds (VIL = 0.8 V, VIH = 2 V), delivers VOH ≥ 2.4 V at IOH = –3 mA, and VOL ≤ 0.4 V at IOL = 8 mA, with disable times (tPZL/tPHZ) under 25 ns and thermal resistance of 67°C/W in the N package.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Type | Noninverting - preserves signal polarity during A↔B data transfer, critical for synchronous bus arbitration without inversion logic overhead. |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL/ALS systems; not rated for 3.3 V operation. |
| Propagation Delay | tPLH/tPHL ≤ 13 ns - enables reliable operation up to ~30 MHz bus toggle rates in point-to-point configurations. |
| Output Drive | IOL = 16 mA / IOH = –15 mA - sufficient to drive 10 ALS loads or 20 LSTTL inputs without buffering. |
| Operating Temperature | 0°C to 70°C - commercial-grade rating; not qualified for extended industrial or automotive temperature ranges. |
| Quiescent Current | ICC ≤ 38 mA at VCC = 5.5 V - higher than CMOS equivalents but typical for bipolar ALS process at full bus activity. |
Pinout & Package
SN74ALS1645AN is housed in a 20-pin plastic dual in-line package (PDIP, N package), 300-mil width, through-hole mountable, with 67°C/W junction-to-ambient thermal resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: LOW enables B→A transfer; HIGH enables A→B transfer. |
| 2 | A1 | Data input/output terminal for A-bus bit 1; bidirectional when enabled, high-Z when OE active HIGH. |
| 3–9 | A2–A8 | A-bus data terminals 2 through 8; identical bidirectional behavior as A1. |
| 10 | GND | Ground reference for all internal circuitry and I/O interfaces. |
| 11–18 | B1–B8 | B-bus data terminals 1 through 8; mirror A-side functionality with direction-dependent signal flow. |
| 19 | OE | Output enable input: ACTIVE HIGH disables all A and B outputs into high-impedance state, isolating buses. |
| 20 | VCC | Positive supply input: must be decoupled locally with 0.1 µF ceramic capacitor near pin. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional 3-state bus interface | Enables shared data paths between microprocessor address/data buses and peripheral modules without external gating logic. |
| ALS-compatible input thresholds | VIL = 0.8 V and VIH = 2.0 V ensure robust noise margin and interoperability with legacy 74ALS/74F logic families. |
| Noninverting data path | Eliminates need for external inverters in A↔B routing, reducing component count and board area in backplane designs. |
| Low disable propagation delay | tPHZ/tPLZ ≤ 12 ns ensures fast bus release during multi-master arbitration or DMA handoff sequences. |
| Standard 20-pin DIP footprint | Supports drop-in replacement in existing through-hole PCB layouts designed for SN74ALS645A or similar octal transceivers. |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
|
Use Scenario: Interfacing an 8-bit microcontroller data bus to a parallel I/O expansion card across a 150 mm backplane trace. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data flow direction via DIR and isolating buses during idle cycles via OE. Use Value: Provides 13 ns max propagation delay and 16 mA drive strength to maintain signal integrity over long traces without repeaters. |
Use Scenario: Adding external SRAM or EPROM to an 8085-based system where address/data multiplexing requires bus separation. IC Role / Device Role / Timing Role: Noninverting transceiver enabling clean A→B read/write cycles while preventing bus contention during memory access windows. Use Value: Matches ALS timing and voltage levels of host CPU, eliminating level-shifting components and simplifying timing budget. |
| Parallel Printer Port Buffer | Test Equipment Bus Coupling |
|
Use Scenario: Isolating and driving Centronics-style parallel printer signals from a microcontroller GPIO port. IC Role / Device Role / Timing Role: Direction-controlled buffer translating MCU port states to printer handshake lines (STROBE, ACK) and data bits. Use Value: 3-state outputs prevent signal contention during printer busy states; OE allows dynamic port reconfiguration. |
Use Scenario: Coupling stimulus/response signals between automated test equipment mainframe and DUT fixture with independent bus domains. IC Role / Device Role / Timing Role: Bidirectional isolation device synchronizing data transfers between mismatched logic families using DIR and OE coordination. Use Value: ALS-compatible thresholds and 25 ns max enable/disable times support deterministic test cycle sequencing within 100 ns windows. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS645N | Same ALS family, noninverting, but lacks DIR pin - uses separate A→B and B→A control inputs (G1/G2). | Requires additional control logic for direction arbitration; less flexible in dynamic bus-sharing scenarios. | Prefer SN74ALS1645AN when single-pin DIR simplifies PCB routing and firmware control. |
| SN74F245N | F-family variant: faster (tPLH ≤ 8 ns), higher ICC (55 mA), lower noise immunity (VIH = 2.0 V same, but VIL = 0.8 V unchanged). | Better suited for high-speed timing-critical paths but increases power and EMI in noise-sensitive environments. | Choose SN74ALS1645AN for lower power and proven stability in legacy industrial systems where 13 ns delay is acceptable. |
Compared with SN74ALS645N and SN74F245N, the SN74ALS1645AN offers integrated direction control in a single pin, lower quiescent current than F-series, and identical ALS voltage compatibility-making it optimal for cost-sensitive, space-constrained upgrades of older 74ALS-based systems.
Availability
SN74ALS1645AN is available at Aetrix Electronics and suitable for industrial backplane interface, legacy memory expansion, and parallel printer port buffering requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS1645AN 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74ALS1645AN belongs to TI's legacy 74ALS logic family, engineered for high-speed, low-power bipolar operation in mid-1980s industrial control and computing systems where reliability and pin compatibility were prioritized over ultra-low power.
FAQ
What logic family does the SN74ALS1645AN belong to, and is it compatible with 74LS devices?
The SN74ALS1645AN is part of the Advanced Low-power Schottky (ALS) logic family. It is electrically compatible with 74LS devices in terms of voltage thresholds (VIH = 2.0 V, VIL = 0.8 V) and output drive, but features faster propagation delays and lower power consumption than standard LS. The SN74ALS1645AN can directly replace 74LS245 in most designs, though layout-level noise margins should be verified due to higher edge rates.
Does the SN74ALS1645AN support 3.3 V operation?
No, the SN74ALS1645AN is specified only for 4.5 V to 5.5 V supply operation and is not characterized for 3.3 V use. Its input thresholds and output voltage levels are optimized for 5 V ALS systems; applying 3.3 V may result in unreliable switching or excessive ICC. For 3.3 V applications, consider modern alternatives like SN74LVC245A instead of the SN74ALS1645AN.
What is the function of the DIR and OE pins on the SN74ALS1645AN?
On the SN74ALS1645AN, DIR (pin 1) controls data direction: LOW enables B→A transfer, HIGH enables A→B transfer. OE (pin 19) is an active-HIGH output enable - when HIGH, all A and B outputs enter high-impedance state, isolating both buses. Both pins must be actively driven; floating OE or DIR may cause undefined bus states or increased ICC in the SN74ALS1645AN.
Can the SN74ALS1645AN be used in place of the SN74ALS1640AN?
No - the SN74ALS1645AN is noninverting, while the SN74ALS1640AN is inverting. Their logic functions differ fundamentally: SN74ALS1640AN complements data during transfer, whereas SN74ALS1645AN preserves polarity. Substituting one for the other without adjusting upstream/downstream logic will invert all transferred data, causing functional failure. Always verify logic polarity before replacing SN74ALS1640AN with SN74ALS1645AN.
What package type and mounting method does the SN74ALS1645AN use?
The SN74ALS1645AN uses a 20-pin plastic dual in-line package (PDIP, "N" suffix), 300-mil width, designed for through-hole mounting. It is not surface-mount compatible. The package has no moisture sensitivity level (MSL) rating, as it is a through-hole ceramic/plastic hybrid unsuitable for reflow soldering; wave soldering or hand-soldering is required. Thermal resistance is 67°C/W (θJA).
SN74ALS1645AN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- 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, 16mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74ALS1645AN FAQ
1.How can I place an order for SN74ALS1645AN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS1645AN 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 SN74ALS1645AN reliable?
The price and inventory of SN74ALS1645AN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS1645AN is usually 5 days.
3.What payment methods are accepted for SN74ALS1645AN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS1645AN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS1645AN?
SN74ALS1645AN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS1645AN 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 SN74ALS1645AN?
For technical support, including SN74ALS1645AN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS1645AN requirements.
6.How does Aetrix verify that SN74ALS1645AN is sourced from the original manufacturer or authorized distributors?
All SN74ALS1645AN 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 SN74ALS1645AN meets industry standards.
7.What is the process for return or replacement of SN74ALS1645AN?
All SN74ALS1645AN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS1645AN, 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 SN74ALS1645AN part is unused and in its original packaging.
Return procedure for SN74ALS1645AN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS1645AN Tags
-
SN74LVC1G17DBVR
Texas Instruments
-
SN74LVC1G07DCKR
Texas Instruments
-
SN74LVC1G17DCKR
Texas Instruments
-
SN74LVC1G07DBVR
Texas Instruments
-
SN74LVC1G125DCKR
Texas Instruments
-
SN74AHCT1G126DBVR
Texas Instruments
-
SN74LVC1G125DBVR
Texas Instruments
-
SN74AHCT1G125DBVR
Texas Instruments
-
SN74LVC2G17DBVR
Texas Instruments
-
SN74LVC2G07DCKR
Texas Instruments
-
SN74LVC1G34DCKR
Texas Instruments
-
SN74LVC2G17DCKR
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
