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Texas Instruments SN74ACT245NS
- Part No.:
- SN74ACT245NS
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ACT245NS.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,558
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Product details
Overview
SN74ACT245NS from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data bus communication between 5-V logic domains. It operates from 4.5 V to 5.5 V, supports TTL-compatible inputs up to 5.5 V, delivers ≤8 ns propagation delay at 5 V, and features independent direction (DIR) and output-enable (OE) controls - used in industrial control backplanes and legacy video interface bridging.
For engineers reviewing the SN74ACT245NS datasheet, SN74ACT245NS pinout, SN74ACT245NS application, or SN74ACT245NS equivalent, key selection criteria include its 20-pin SO package, 3-state bus isolation capability, ±24 mA drive strength, thermal resistance of 99.7 °C/W, and compatibility with mixed-voltage system interconnects requiring level-tolerant I/O.
Technical Context
The SN74ACT245NS implements dual 8-bit bidirectional data paths controlled by DIR and OE signals, enabling A-to-B or B-to-A data flow without external timing circuitry. Its ACT logic family provides CMOS-level power efficiency with bipolar-like drive strength and TTL-voltage compatibility on all inputs.
It uses a noninverting transceiver architecture with high-impedance outputs when OE is high, and includes overvoltage-tolerant inputs rated to 5.5 V regardless of VCC. The device is specified for operation from –40°C to +85°C and features 4.5 pF input capacitance and 15 pF I/O capacitance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures stable operation across standard 5-V supply tolerances and brown-out resilience. |
| Max Propagation Delay | 8 ns at 5 V - enables reliable timing in high-speed parallel bus systems up to ~100 MHz clock-equivalent rates. |
| Output Drive | ±24 mA per pin - sufficient to drive standard TTL loads and moderate PCB trace capacitance without external buffers. |
| Input Voltage Tolerance | Up to 5.5 V - allows interfacing with 5-V peripherals even when VCC is at minimum 4.5 V, preventing input clamping. |
| Thermal Resistance | 99.7 °C/W (θJA) - defines junction-to-ambient rise under typical SO-20 board layout, guiding thermal derating. |
| I/O Capacitance | 15 pF - directly impacts signal integrity and maximum achievable edge rate on loaded buses. |
| ESD Rating | ±3000 V HBM - meets industrial handling requirements without additional protection circuitry. |
Pinout & Package
SN74ACT245NS is housed in a 20-pin small-outline package (SO, NS), measuring 12.6 mm × 7.8 mm overall with a 12.6 mm × 5.3 mm body. Pin 1 is located at the top-left corner adjacent to the index notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control input: low = B→A, high = A→B; determines data flow path during active state. |
| 2–9 | A1–A8 | Port A bidirectional I/Os - connect to one data bus segment; driven or sensed depending on DIR and OE. |
| 10 | GND | Ground reference for logic and power return - must be low-impedance for noise immunity. |
| 11–18 | B8–B1 | Port B bidirectional I/Os - connect to second data bus segment; pin order reversed for routing convenience. |
| 19 | OE | Active-low output enable - high disables both ports into high-impedance, isolating buses. |
| 20 | VCC | Positive supply pin - requires local 0.1 µF bypass capacitor to suppress switching noise. |
Key Features
| Feature | Design Value |
|---|---|
| TTL-compatible inputs | Accepts 0–5.5 V input voltages independent of VCC, enabling robust interfacing with legacy 5-V logic families. |
| Asynchronous bidirectional control | DIR and OE operate independently - no clock or synchronization required for bus direction or isolation changes. |
| Low-output ringing design | Slower edge rates minimize overshoot/undershoot on unterminated or lightly loaded PCB traces. |
| High-impedance isolation | When OE is high, both A and B ports present >10 MΩ impedance - prevents bus contention and leakage current paths. |
| Wide temperature range | Specified from –40°C to +85°C - suitable for industrial control cabinets and factory automation environments. |
Applications
| Industrial Backplane Interconnect | Legacy Video Signal Routing |
|---|---|
|
Use Scenario: Isolating and translating data between microcontroller subsystems and FPGA-based I/O expansion modules in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver providing voltage-level consistent data handoff between 5-V MCU and 5-V peripheral buses. Use Value: Eliminates need for discrete level shifters while maintaining timing margins via 8 ns tPD and 24 mA drive into 50-pF loads. |
Use Scenario: Routing parallel RGB or sync/data signals between aging SDI receiver boards and modern display controller cards in broadcast signage systems. IC Role / Device Role / Timing Role: Bus isolator enabling hot-swap-safe insertion of new processing modules without disrupting active video streams. Use Value: High-impedance disable state (OE-controlled) prevents signal corruption during board insertion/removal sequences. |
| Appliance Control Panel Interface | Factory Automation Sensor Hub |
|
Use Scenario: Connecting touch-panel microcontrollers to main appliance control boards where EMI and voltage mismatch are concerns. IC Role / Device Role / Timing Role: Level-tolerant transceiver buffering noisy panel I/O lines from sensitive mainboard logic. Use Value: 5.5-V input tolerance accommodates transient spikes on long ribbon cables without clamping diodes. |
Use Scenario: Aggregating digital sensor outputs (e.g., limit switches, encoders) onto a shared 8-bit status bus in modular machine tool controllers. IC Role / Device Role / Timing Role: Data concentrator enabling multiple sensors to share one microcontroller port with directional arbitration. Use Value: DIR-controlled flow direction allows centralized polling of sensor banks without dedicated read/write lines. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LVC245A | 3.3-V only operation (1.65–3.6 V); lower drive (±24 mA), faster tPD (5.3 ns), smaller VSSOP package option. | Requires level-shifting when interfacing with 5-V buses; unsuitable for pure 5-V systems without translation. | Select SN74LVC245A only if migrating to 3.3-V logic domains or prioritizing speed/power over 5-V compatibility. |
| SN74HCT245 | Same 5-V operation (4.5–5.5 V); identical pinout and function but higher ICC (max 80 µA vs 40 µA), slightly slower tPD (11 ns). | Compatible drop-in replacement with relaxed timing margin; better noise immunity due to HCT input thresholds. | Choose SN74HCT245 for cost-sensitive industrial designs where 11 ns delay is acceptable and HCT's noise rejection is beneficial. |
Compared with SN74LVC245A and SN74HCT245, the SN74ACT245NS offers optimal balance of 5-V native operation, 8 ns speed, and TTL-input compatibility - making it the preferred choice for legacy 5-V bus bridging where level translation is undesirable and timing headroom is constrained.
Availability
SN74ACT245NS is available at Aetrix Electronics and suitable for industrial backplane interconnect, legacy video signal routing, appliance control panel interface, and factory automation sensor hub applications requiring stable component supply and long-term obsolescence management.
Supply support for SN74ACT245NS 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 over 50 years of innovation in industrial and automotive electronics.
The SN74ACT245NS belongs to TI's ACT logic family - engineered for high-speed, low-noise 5-V bus interfacing in industrial control, test equipment, and legacy system upgrades where reliability and voltage tolerance are critical.
FAQ
What is the operating voltage range for SN74ACT245NS?
The SN74ACT245NS operates from 4.5 V to 5.5 V. This range ensures compatibility with standard 5-V power supplies including those with ±10% tolerance. Operation outside this range may cause functional failure or permanent damage, and the device is not rated for 3.3-V-only use. All electrical characteristics in the datasheet are guaranteed within this window.
Does SN74ACT245NS support 3.3-V logic inputs?
Yes, SN74ACT245NS accepts 3.3-V logic inputs reliably because its VIH threshold is 2.0 V and VIL is 0.8 V at 5-V VCC - well within 3.3-V CMOS logic levels. However, the device itself must be powered at 4.5–5.5 V; it does not operate from a 3.3-V supply. Inputs remain overvoltage tolerant up to 5.5 V regardless of VCC.
Can SN74ACT245NS be used as a unidirectional buffer?
Yes, SN74ACT245NS can function as a unidirectional buffer by fixing the DIR pin to a constant logic level (high for A→B, low for B→A) and using OE to enable/disable the path. This configuration is common in fixed-data-path applications such as memory address latching or peripheral select line buffering, where bidirectional capability is unused but pin compatibility is retained.
What is the thermal performance of SN74ACT245NS in its SO package?
The SN74ACT245NS in the NS (SO-20) package has a junction-to-ambient thermal resistance (θJA) of 99.7 °C/W under standard JEDEC test conditions. At full 200 mA total output current, self-heating remains within safe limits for industrial ambient temperatures up to +85°C when mounted on a 2-layer PCB with adequate copper pour around GND/VCC pins.
Is SN74ACT245NS pin-compatible with other 245-series transceivers?
SN74ACT245NS shares identical pinout and function with SN74HCT245, SN74LS245, and SN74ALS245 in the same SO-20 package. However, differences in drive strength, propagation delay, and input thresholds mean direct substitution requires validation of timing margins and noise immunity in the target application. Electrical behavior is not identical despite mechanical compatibility.
SN74ACT245NS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ACT
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tube
- 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:
- 24mA, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74ACT245NS FAQ
1.How can I place an order for SN74ACT245NS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ACT245NS 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 SN74ACT245NS reliable?
The price and inventory of SN74ACT245NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ACT245NS is usually 5 days.
3.What payment methods are accepted for SN74ACT245NS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ACT245NS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ACT245NS?
SN74ACT245NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ACT245NS 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 SN74ACT245NS?
For technical support, including SN74ACT245NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ACT245NS requirements.
6.How does Aetrix verify that SN74ACT245NS is sourced from the original manufacturer or authorized distributors?
All SN74ACT245NS 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 SN74ACT245NS meets industry standards.
7.What is the process for return or replacement of SN74ACT245NS?
All SN74ACT245NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74ACT245NS, 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 SN74ACT245NS part is unused and in its original packaging.
Return procedure for SN74ACT245NS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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