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Texas Instruments SN74AS244AN
- Part No.:
- SN74AS244AN
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74AS244AN.pdf
- Description:
- IC BUF NON-INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:121
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Product details
Overview
SN74AS244AN from Texas Instruments is an octal non-inverting buffer/line driver with 3-state outputs, designed for memory address driving, bus interfacing, and clock distribution in TTL-compatible systems. It operates from 4.5 V to 5.5 V, delivers ±15 mA output drive, supports 0°C to 70°C industrial temperature range, and features pnp-input circuitry to reduce DC loading on upstream logic. It is commonly used in legacy industrial control backplanes and discrete bus arbitration circuits.
For engineers reviewing the SN74AS244AN datasheet, SN74AS244AN pinout, SN74AS244AN application, or SN74AS244AN equivalent, key selection criteria include its 3-state enable timing (tPZL ≤ 7.5 ns), low-level output current capability (IOL = 64 mA), compatibility with standard 20-pin PDIP layout, and direct replacement suitability in AS-family buffered address/data paths.
Technical Context
This device implements two independent 4-bit non-inverting buffer groups, each controlled by a dedicated active-low 3-state enable input (1OE, 2OE). Its bipolar AS-family architecture provides faster switching than ALS variants - tPHL/tPLH ≤ 6.2 ns at VCC = 5 V, CL = 50 pF - while maintaining TTL voltage thresholds (VIH = 2 V, VIL = 0.8 V).
The pnp-based input stage minimizes input current draw (IIL = –1 mA max), reducing loading on preceding gates. Output disable leakage (IOZL = –50 µA) and high-impedance state integrity are specified across full temperature and supply ranges, ensuring reliable bus contention avoidance in multi-driver configurations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL power rails and tolerates nominal supply variation. |
| IOL (Low-level) | 64 mA - enables direct drive of multiple TTL inputs or moderate-current loads without external buffering. |
| tPHL / tPLH | ≤ 6.2 ns - supports high-speed address/data latching in sub-10 ns timing-critical bus cycles. |
| VIH / VIL | 2.0 V / 0.8 V - guarantees interoperability with standard TTL and LS logic families without level shifting. |
| Operating Temp | 0°C to 70°C - qualified for commercial and industrial embedded applications with passive cooling. |
| ICC (Outputs Low) | 60–90 mA - informs power budgeting for worst-case active-drive scenarios in dense PCB layouts. |
| 3-State Enable Delay | tPZL ≤ 7.5 ns, tPHZ ≤ 6 ns - determines minimum bus turnaround time between driver releases and new driver assertions. |
Pinout & Package
SN74AS244AN uses a 20-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard through-hole mounting and 2.54 mm pin pitch. Pin 1 is located at the top-left corner adjacent to the notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE | Active-low enable for Group 1 (Y1–Y4) | Drives all four outputs of first buffer group into high-impedance when high; must be pulled low for functional output. |
| 1A1–1A4 | Inputs for Group 1 buffers | Non-inverting data inputs corresponding to outputs Y1–Y4; accept standard TTL logic levels. |
| 1Y1–1Y4 | Outputs for Group 1 buffers | 3-state, non-inverting outputs sourced/sunk via internal bipolar transistors; rated for 64 mA sink. |
| GND (Pin 10) | Ground reference | Primary return path for all input/output currents and internal bias networks; requires low-impedance PCB connection. |
| VCC (Pin 20) | Positive supply | Power rail for internal logic and output drivers; decoupling capacitor (0.1 µF) required within 1 cm of this pin. |
| 2OE | Active-low enable for Group 2 (Y5–Y8) | Independent control for second buffer group; allows asymmetric bus partitioning or staggered enable sequencing. |
| 2A1–2A4 | Inputs for Group 2 buffers | Electrically isolated from Group 1 inputs; supports separate data streams or mirrored signal distribution. |
| 2Y1–2Y4 | Outputs for Group 2 buffers | Match Group 1 output characteristics; identical drive strength, timing, and 3-state behavior. |
Key Features
| Feature | Design Value |
|---|---|
| Octal 3-state buffering | Two independent 4-bit groups with separate OE controls enable flexible bus segmentation and hot-swap-safe I/O isolation. |
| AS-family speed grade | 6.2 ns max propagation delay exceeds ALS performance, enabling use in higher-frequency address latching and clock fanout. |
| pnp input structure | Reduces input current to –1 mA max, lowering loading on preceding gate outputs and improving fanout capacity. |
| 64 mA output sink | Supports direct interface to multiple TTL loads or small LEDs without series resistors in low-voltage drop configurations. |
| TTL-compatible thresholds | 2.0 V VIH and 0.8 V VIL ensure seamless integration with legacy 74xx, 74LSxx, and microcontroller GPIOs operating at 5 V. |
Applications
| Memory Address Buffering | Parallel Bus Isolation |
|---|---|
Use Scenario: Driving 16-bit address lines from a microprocessor to multiple memory ICs on a shared bus. IC Role / Device Role / Timing Role: Non-inverting buffer with 3-state control isolates CPU address outputs during DMA or peripheral access cycles. Use Value: Prevents bus contention by enabling/disabling address drivers synchronously with memory select signals, leveraging tPZL ≤ 7.5 ns for tight timing margins. | Use Scenario: Interfacing a microcontroller's parallel port to external peripherals with independent enable requirements. IC Role / Device Role / Timing Role: Dual-group 3-state driver allows selective activation of subsets of I/O lines without software reconfiguration. Use Value: Enables hardware-controlled peripheral arbitration using discrete OE signals, eliminating need for software bit-banging or additional logic. |
| Clock Distribution | Legacy Industrial Backplane |
Use Scenario: Fanout of a system clock to multiple synchronous logic blocks requiring matched edge timing. IC Role / Device Role / Timing Role: Low-skew buffer delivering identical rising/falling delays (tPLH/tPHL ≤ 6.2 ns) across all eight outputs. Use Value: Maintains <100 ps inter-output skew under matched load conditions, preserving setup/hold timing for downstream flip-flops. | Use Scenario: Signal conditioning and level restoration in aging PLC or CNC controller backplanes with mixed logic families. IC Role / Device Role / Timing Role: Voltage-level translator and current booster between LS-TTL control logic and higher-current relay drivers. Use Value: Compensates for signal degradation over long traces via 64 mA drive strength and noise-immune TTL thresholds. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal 3-state buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS244AN | Slower propagation (tPHL ≤ 10 ns), lower IOL (24 mA), reduced power consumption (ICC ≤ 24 mA). | Suitable for cost-sensitive, lower-speed designs where timing margin is >10 ns and drive strength ≤24 mA suffices. | Select SN74ALS244AN only if system timing budget allows ≥3.8 ns slower response and load current demand is ≤24 mA per output. |
| SN74F244N | Fast TTL variant with tPHL ≤ 6.5 ns but higher ICC (outputs low: 80 mA) and no pnp input optimization (IIL = –1.6 mA). | Better suited for high-speed, low-latency paths where input loading is less critical than raw speed. | Choose SN74F244N when prioritizing minimal propagation delay over input current reduction and power efficiency. |
Compared with SN74ALS244AN and SN74F244N, SN74AS244AN uniquely balances high-speed operation (6.2 ns), strong output drive (64 mA), and low input loading (–1 mA), making it optimal for timing-critical industrial bus interfaces where both speed and signal integrity matter.
Availability
SN74AS244AN is available at Aetrix Electronics and suitable for memory address buffering, parallel bus isolation, and clock distribution applications requiring stable component supply and long-term industrial availability.
Supply support for SN74AS244AN 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 solutions for industrial, automotive, and communications markets.
The SN74AS244AN belongs to TI's 74AS logic family, engineered for high-speed, low-noise digital interfacing in legacy and upgrade systems where TTL compatibility and robust 3-state control are essential.
FAQ
What is the maximum operating supply voltage for SN74AS244AN?
The absolute maximum supply voltage for SN74AS244AN is 7 V, but the recommended operating range is strictly 4.5 V to 5.5 V. Operation outside this window may cause undefined logic states or accelerated parametric drift. The SN74AS244AN datasheet specifies electrical characteristics only within the 4.5–5.5 V band, and sustained use above 5.5 V risks permanent damage to internal bipolar junctions.
Does SN74AS244AN support mixed-voltage interfacing with 3.3 V logic?
SN74AS244AN is not 3.3 V tolerant: its VIH minimum is 2.0 V and VIL maximum is 0.8 V, which aligns with 5 V TTL but creates marginal noise margins with 3.3 V CMOS outputs. Direct connection risks unreliable high-level detection. For 3.3 V-to-5 V interfacing, SN74AS244AN requires a level-shifting buffer or resistor-divider network to ensure VIH ≥ 2.0 V under worst-case conditions.
How does the pnp input structure in SN74AS244AN improve system design?
The pnp input stage in SN74AS244AN reduces input current draw to –1 mA maximum (vs –1.6 mA in F-series), decreasing loading on upstream drivers and increasing fanout capability. This allows one SN7400-series gate to reliably drive more SN74AS244AN inputs without signal degradation, simplifying board-level timing analysis and reducing need for intermediate buffering in dense logic arrays.
Can SN74AS244AN outputs be paralleled for higher current drive?
No - SN74AS244AN outputs must never be paralleled while enabled, as minor propagation delay mismatches (even <100 ps) can cause momentary shoot-through currents exceeding safe limits. The device's 3-state architecture is intended for bus sharing, not current combining. For >64 mA per line, use discrete MOSFETs or dedicated high-current drivers instead of paralleling SN74AS244AN outputs.
What is the thermal derating behavior of SN74AS244AN above 25°C ambient?
SN74AS244AN has no published thermal derating curve, but its maximum operating temperature is fixed at 70°C. At elevated ambient temperatures, output current capability (IOL) remains rated at 64 mA only if junction temperature stays within limits - requiring ≤20°C/W PCB thermal resistance for continuous 64 mA operation at 70°C ambient. Derating is implicit via the absolute maximum junction temperature of 150°C; users must calculate θJA based on actual copper area and airflow.
SN74AS244AN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- Buffer, Non-Inverting
- Number of Elements:
- 2
- Number of Bits per Element:
- 4
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 15mA, 64mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74AS244AN FAQ
1.How can I place an order for SN74AS244AN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS244AN 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 SN74AS244AN reliable?
The price and inventory of SN74AS244AN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS244AN is usually 5 days.
3.What payment methods are accepted for SN74AS244AN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS244AN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS244AN?
SN74AS244AN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS244AN 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 SN74AS244AN?
For technical support, including SN74AS244AN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS244AN requirements.
6.How does Aetrix verify that SN74AS244AN is sourced from the original manufacturer or authorized distributors?
All SN74AS244AN 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 SN74AS244AN meets industry standards.
7.What is the process for return or replacement of SN74AS244AN?
All SN74AS244AN units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS244AN, 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 SN74AS244AN part is unused and in its original packaging.
Return procedure for SN74AS244AN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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