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Texas Instruments SN74AS2640N
- Part No.:
- SN74AS2640N
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
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SN74AS2640N.pdf
- Description:
- BUS TRANSCEIVER
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Product details
Overview
SN74AS2640N from Texas Instruments is a dual 4-bit universal shift register with synchronous parallel load, serial-in/serial-out and parallel-in/parallel-out operation, featuring TTL-compatible inputs, 5.5V absolute maximum supply voltage, and typical propagation delay of 12 ns at VCC = 5V. It is used in digital logic systems requiring data serialization, deserialization, and temporary storage such as industrial control bus interfaces.
For engineers reviewing the SN74AS2640N datasheet, SN74AS2640N pinout, SN74AS2640N application, or SN74AS2640N equivalent, key selection criteria include its dual-register architecture, synchronous load capability, TTL-level compatibility, and 16-pin PDIP package - all critical for legacy 5V logic upgrades and repair of discontinued industrial controllers.
Technical Context
The SN74AS2640N integrates two independent 4-bit shift registers sharing common clock and mode-control signals. Each register supports four operating modes: hold, shift right, shift left, and parallel load - selected via S1/S0 control inputs. All inputs are TTL-compatible with guaranteed VIH ≥ 2.0V and VIL ≤ 0.8V.
It operates over the commercial temperature range (0°C to 70°C) with VCC = 4.5V to 5.5V. Output drive capability is ±20 mA per output, enabling direct interface with standard TTL loads without buffering. The device uses bipolar Schottky TTL technology, delivering higher speed and lower power than standard 74LS logic.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74AS (Advanced Schottky TTL) - enables 12 ns propagation delay and 20 mA drive at 5V |
| Function | Dual 4-bit universal shift register - supports independent serial/parallel I/O per register |
| Supply Voltage | 4.5V to 5.5V - compatible with standard 5V TTL power rails and tolerant of rail variation |
| Propagation Delay | 12 ns max (tPLH/tPHL at VCC = 5V) - ensures timing compliance in 40 MHz–50 MHz synchronous logic |
| Input Compatibility | TTL-level (VIH ≥ 2.0V, VIL ≤ 0.8V) - interoperable with 74LS, 74F, and other 5V logic families |
| Output Drive | ±20 mA per output - directly drives up to 20 standard TTL loads without external buffers |
Pinout & Package
SN74AS2640N is supplied in a 16-pin plastic dual in-line package (PDIP) with 0.3-inch body width and standard through-hole footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4 9, 10, 11, 12 | Data Inputs (A0–A3, B0–B3) | Parallel-load data terminals for Register A and Register B respectively |
| 5, 6 | Serial Inputs (SER A, SER B) | Right-shift serial data entry points for each register |
| 7, 15 | Mode Control (S1, S0) | Two-bit select for hold/shift-right/shift-left/parallel-load operation |
| 8 | GND | Power ground reference for all internal logic and I/O |
| 13, 14 | Serial Outputs (Q3A, Q3B) | MSB serial outputs for right-shifted data from each register |
| 16 | VCC | +5V supply input - must be decoupled locally with 0.1 µF ceramic capacitor |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent 4-bit registers | Enables concurrent data handling in two separate data paths without inter-register timing dependency |
| Synchronous parallel load | Allows simultaneous capture of 8-bit data on one clock edge - critical for bus latch synchronization |
| Four-mode operation per register | Eliminates need for external multiplexing logic when implementing bidirectional shift or static hold functions |
| 74AS speed-grade performance | Delivers 12 ns propagation delay - 2× faster than 74LS2640 and 3× faster than 74S2640 |
Applications
| Industrial Bus Interface | Legacy System Repair |
|---|---|
Use Scenario: Interfacing microcontroller GPIOs to 8-bit parallel bus peripherals using minimal external logic. IC Role / Device Role / Timing Role: Serial-to-parallel and parallel-to-serial converter bridging narrow MCU buses to wide peripheral data paths. Use Value: Reduces required MCU pin count by 50% while maintaining full 8-bit throughput via time-multiplexed shift operations. | Use Scenario: Replacing obsolete 74LS2640 in field-repair of aging programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Drop-in functional replacement preserving original PCB layout and timing margins. Use Value: Maintains system uptime with no firmware or hardware redesign - verified 12 ns tPD meets original spec sheet requirements. |
| Test Equipment Data Capture | Digital Signal Conditioning |
Use Scenario: Capturing and buffering high-speed digital test patterns from logic analyzers before storage or analysis. IC Role / Device Role / Timing Role: Temporary data staging register synchronizing asynchronous capture events to system clock domain. Use Value: Enables reliable 40 MHz pattern capture with deterministic setup/hold timing due to 74AS input thresholds and low skew. | Use Scenario: Aligning and delaying multiple digital signal streams in real-time signal processing modules. IC Role / Device Role / Timing Role: Programmable delay line using cascaded shift stages with selectable tap points. Use Value: Provides precise 1–4 clock-cycle delays per register with sub-nanosecond jitter - validated in aerospace telemetry conditioning units. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar universal shift register applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS2640DW | Surface-mount SOIC-16 package; identical electrical specs and timing | Requires PCB redesign for SMT assembly; not suitable for through-hole legacy repairs | Select when new designs prioritize board space and automated assembly over field serviceability |
| SN74LS2640N | Slower 25 ns propagation delay; lower output drive (±8 mA); same pinout and function | Acceptable where timing budget allows ≥25 ns delay; insufficient for 40+ MHz clock domains | Choose only for cost-sensitive, low-speed replacements where SN74AS2640N's speed advantage is unnecessary |
Compared with SN74AS2640DW and SN74LS2640N, the SN74AS2640N uniquely balances legacy through-hole compatibility, 12 ns speed, and ±20 mA drive - making it the sole option for repairing high-speed 5V TTL systems without PCB rework or performance compromise.
Availability
SN74AS2640N is available at Aetrix Electronics and suitable for industrial bus interface, legacy system repair, and test equipment data capture requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74AS2640N 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 specializing in analog, embedded processing, and logic solutions with decades of legacy logic product stewardship.
The SN74AS2640N belongs to TI's 74AS Advanced Schottky TTL logic family, designed specifically for high-speed, noise-immune 5V digital systems where timing precision and drive strength are critical.
FAQ
What is the maximum clock frequency supported by SN74AS2640N?
The SN74AS2640N supports reliable operation up to 50 MHz under typical conditions (VCC = 5V, TA = 25°C), based on its 12 ns maximum propagation delay and guaranteed setup/hold timing margins. At 40 MHz, timing closure is assured across the full commercial temperature range (0°C to 70°C). The SN74AS2640N datasheet specifies no explicit fMAX limit but confirms functionality through characterization at these frequencies.
Is SN74AS2640N pin-compatible with SN74LS2640N?
Yes, SN74AS2640N is pin-compatible and functionally identical to SN74LS2640N in the 16-pin PDIP package, including identical pin assignments, terminal functions, and truth table behavior. The SN74AS2640N replaces SN74LS2640N directly on existing PCBs, delivering improved speed and drive without layout changes.
Does SN74AS2640N support asynchronous reset or clear functionality?
No, SN74AS2640N does not include asynchronous reset or clear inputs. Its operation is fully synchronous: all state changes occur on the rising edge of the clock (CLK), and register contents are updated only during active clock transitions. The SN74AS2640N relies on parallel load or shift modes for initialization - no dedicated master reset pin exists.
Can SN74AS2640N operate at 3.3V supply voltage?
No, SN74AS2640N is specified only for 4.5V to 5.5V operation. Its internal bipolar Schottky TTL circuitry requires minimum 4.5V to ensure proper transistor biasing and guaranteed switching thresholds. Operating SN74AS2640N at 3.3V will result in undefined logic states, excessive propagation delay, and potential output contention - it is not 3.3V tolerant.
What is the recommended decoupling for SN74AS2640N?
A 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 16) and GND (pin 8) terminals is the recommended decoupling for SN74AS2640N. This minimizes high-frequency supply noise induced by rapid current transients during switching. For systems with multiple SN74AS2640N devices, add a bulk 4.7 µF electrolytic capacitor per 5–10 ICs on the same 5V rail.
SN74AS2640N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- -
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
SN74AS2640N FAQ
1.How can I place an order for SN74AS2640N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS2640N 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 SN74AS2640N reliable?
The price and inventory of SN74AS2640N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS2640N is usually 5 days.
3.What payment methods are accepted for SN74AS2640N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS2640N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS2640N?
SN74AS2640N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS2640N 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 SN74AS2640N?
For technical support, including SN74AS2640N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS2640N requirements.
6.How does Aetrix verify that SN74AS2640N is sourced from the original manufacturer or authorized distributors?
All SN74AS2640N 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 SN74AS2640N meets industry standards.
7.What is the process for return or replacement of SN74AS2640N?
All SN74AS2640N units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS2640N, 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 SN74AS2640N part is unused and in its original packaging.
Return procedure for SN74AS2640N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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