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Texas Instruments SN74LS245DBRG4
- Part No.:
- SN74LS245DBRG4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
SN74LS245DBRG4.pdf
- Description:
- IC TXRX NON-INVERT 5.25V 20SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,914
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Product details
Overview
SN74LS245DBRG4 from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in TTL-level systems. It features direction control (DIR), active-low output enable (OE), 8 ns typical propagation delay, ±15 mA output drive capability, and operates at 5 V supply voltage. It is used in industrial backplane interfaces and ribbon-cable-based data links where bus isolation and signal integrity are critical.
For engineers reviewing the SN74LS245DBRG4 datasheet, SN74LS245DBRG4 pinout, SN74LS245DBRG4 application, or SN74LS245DBRG4 equivalent, key selection considerations include its SSOP-20 package, 0°C to 70°C operating temperature range, 3-state bus isolation behavior, and compatibility with legacy LS-TTL logic families in embedded control and test equipment designs.
Technical Context
The SN74LS245DBRG4 implements Schottky transistor logic (LS) with PNP inputs to reduce DC loading on shared bus lines. Its internal architecture supports two functional modes: bidirectional data flow (A↔B) controlled by DIR, and high-impedance isolation when OE is asserted high.
It delivers 24 mA sink and –15 mA source current per channel under recommended conditions, with built-in input hysteresis (0.2–0.4 V) improving noise immunity on bus signals. Propagation delay is tightly specified at 8–12 ns (tPLH/tPHL), and output enable/disable timing is characterized at 15–40 ns.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - ensures compatibility with legacy 74LS series, predictable voltage thresholds, and robust noise margins. |
| Supply Voltage | 4.75 V to 5.25 V - requires stable 5 V rail; operation outside this range risks undefined logic states or damage. |
| Output Drive | 24 mA sink / –15 mA source - sufficient to drive multiple TTL loads or long traces without external buffering. |
| Propagation Delay | 8–12 ns (A↔B) - enables reliable operation up to ~50 MHz in short-bus configurations with light capacitive load. |
| Input Hysteresis | 0.2–0.4 V - increases effective noise margin on bus inputs, reducing susceptibility to ringing or slow-edge-induced glitches. |
| Operating Temperature | 0°C to 70°C - rated for commercial-grade applications including factory automation and point-of-sale terminals. |
| ESD Rating | ±2500 V HBM - meets standard handling requirements for assembly in non-classified environments. |
Pinout & Package
SN74LS245DBRG4 is housed in a 20-pin SSOP (Shrink Small Outline Package) with 0.65 mm lead pitch and 7.20 mm × 5.30 mm body size. The package is RoHS-compliant, moisture-sensitive level 1 (unlimited reflow), and optimized for surface-mount assembly on dense PCBs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data flow; High = A→B data flow; determines real-time bus directionality without reset. |
| 2–9 (A1–A8) | Bidirectional I/O (A-side) | Connects to local bus; functions as input or output depending on DIR state; internally terminated with PNP inputs. |
| 10 (GND) | Ground Reference | Primary return path for all logic and output currents; must be low-impedance and decoupled near VCC pin. |
| 11–18 (B8–B1) | Bidirectional I/O (B-side) | Connects to remote bus or peripheral; mirrors A-side functionality with reversed numbering order. |
| 19 (OE) | Active-Low Output Enable | Low = all channels enabled; High = all A/B pins enter high-impedance state, isolating both buses. |
| 20 (VCC) | Power Supply | +5 V supply input; requires local 0.1 µF ceramic bypass capacitor placed adjacent to pin for noise suppression. |
Key Features
| Feature | Design Value |
|---|---|
| 3-State Outputs | Enables true bus contention avoidance: all eight channels simultaneously enter high-Z when OE is high, allowing multiple devices to share one physical bus. |
| PNP Input Structure | Reduces steady-state DC loading on driven bus lines - critical for maintaining valid logic levels across long ribbon cables or daisy-chained backplanes. |
| Input Hysteresis | 0.2–0.4 V threshold separation improves noise rejection on slow-rising/falling bus signals, preventing metastability during edge transitions. |
| Standard '245 Pinout | Ensures drop-in replacement compatibility with other industry-standard octal transceivers (e.g., 74LS245, 74ALS245) in existing PCB layouts. |
| LS-TTL Electrical Compatibility | Guarantees interoperability with legacy 74LS, 74S, and 74F logic families without level-shifting circuitry in mixed-logic systems. |
Applications
| Industrial Backplane Interface | Ribbon-Cable Data Link |
|---|---|
|
Use Scenario: Interfacing microcontroller-based master modules with distributed I/O slave cards across a 20+ cm backplane. IC Role / Device Role / Timing Role: Bidirectional bus repeater that buffers and isolates address/data/control lines between mismatched drive-strength domains. Use Value: Prevents signal degradation over long traces by providing 24 mA drive strength and hysteresis-enhanced noise immunity, extending reliable communication distance. |
Use Scenario: Connecting a PLC CPU module to remote sensor/actuator racks via 36-conductor flat ribbon cable. IC Role / Device Role / Timing Role: Direction-controlled transceiver enabling full-duplex data exchange while supporting hot-swap isolation via OE control. Use Value: Eliminates bus contention during rack insertion/removal by disabling outputs (OE high), protecting both controller and peripherals from latch-up or overcurrent. |
| Factory Automation Controller | Electronic Point-of-Sale Terminal |
|
Use Scenario: Isolating programmable logic controller (PLC) CPU bus from field I/O expansion modules subject to EMI and ground potential differences. IC Role / Device Role / Timing Role: Galvanically isolated bus interface (via physical separation + 3-state control) preventing ground loop currents from corrupting digital signals. Use Value: Maintains data integrity in electrically noisy factory environments where common-mode noise exceeds 1 Vpp on shared bus lines. |
Use Scenario: Extending parallel printer or cash drawer interface from POS terminal motherboard to peripheral enclosure using compact flat cable. IC Role / Device Role / Timing Role: Level-matched bus driver ensuring TTL-compatible signal swing and timing compliance across mechanically constrained interconnects. Use Value: Enables reliable 1–2 MBps parallel data transfer over 15 cm ribbon cable without signal reflection or timing skew issues. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS245N | PDIP-20 package; larger footprint (24.33 mm × 6.35 mm); through-hole mounting; same electrical specs and pinout. | Suitable for prototyping, manual assembly, or legacy through-hole production lines; lacks SSOP's space efficiency. | Select SN74LS245N when board assembly uses through-hole processes or requires socket-based testing/debugging. |
| SN74ALS245N | Advanced LS family: lower power (ICC ≈ 35 mA vs. 70 mA), faster propagation (6 ns typ), higher noise immunity, but reduced output drive (–12 mA/12 mA). | Better for high-speed, low-power systems where bus capacitance is low and drive strength demand is moderate. | Choose SN74ALS245N only if system timing budget allows tighter delays and power consumption is prioritized over drive capability. |
Compared with SN74LS245N, SN74LS245DBRG4 offers superior PCB density and automated assembly compatibility; compared with SN74ALS245N, it provides higher output current for driving heavier bus loads, making it preferable in industrial backplane and ribbon-cable applications where signal integrity under load is critical.
Availability
SN74LS245DBRG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, factory automation controllers, and electronic point-of-sale terminals requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS245DBRG4 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 ICs with broad industrial and automotive qualification.
SN74LS245DBRG4 belongs to TI's legacy 74LS logic product line, engineered for reliability in commercial-grade digital systems requiring proven TTL compatibility, deterministic timing, and robust bus interfacing.
FAQ
What is the function of the DIR pin on the SN74LS245DBRG4?
The DIR (direction) pin on the SN74LS245DBRG4 controls data flow direction between the A and B buses. When DIR is logic high, data transfers from the A-side inputs to the B-side outputs; when DIR is logic low, data flows from B to A. This bidirectional control is synchronous with the output-enable state and requires no clock or setup time, enabling simple, real-time bus arbitration in the SN74LS245DBRG4.
Can the SN74LS245DBRG4 operate with a 3.3 V supply?
No, the SN74LS245DBRG4 is not rated for 3.3 V operation. Its recommended supply voltage is 4.75 V to 5.25 V, and absolute maximum VCC is 7 V. Operating below 4.75 V may cause marginal logic thresholds, increased propagation delay, or failure to meet output drive specifications. For 3.3 V systems, consider modern alternatives like SN74LVC245A, not the SN74LS245DBRG4.
How does the OE pin affect bus isolation in the SN74LS245DBRG4?
The OE (output enable) pin on the SN74LS245DBRG4 is active-low: when held low, all eight A/B channels are enabled for bidirectional data transfer; when pulled high, all outputs enter high-impedance (3-state) mode, effectively isolating the A and B buses from each other. This isolation prevents bus contention and allows safe hot-plug operation - a core design feature of the SN74LS245DBRG4.
What is the maximum capacitive load the SN74LS245DBRG4 can drive reliably?
The SN74LS245DBRG4 is characterized for CL = 45 pF in switching tests (tPLH/tPHL = 8–12 ns). While it can drive higher capacitance, performance degrades: propagation delay increases linearly with load, and ringing may occur above ~60 pF without proper termination. For reliable operation beyond 45 pF, add series resistors or use controlled-impedance routing - confirmed in SN74LS245DBRG4 application guidance.
Is the SN74LS245DBRG4 pin-compatible with other 74LS245 variants?
Yes, the SN74LS245DBRG4 shares the industry-standard '245 pinout across all package variants (SSOP, PDIP, SOIC, etc.). Pin 1 is DIR, pins 2–9 are A1–A8, pin 10 is GND, pins 11–18 are B8–B1 (reversed order), pin 19 is OE, and pin 20 is VCC. This uniformity allows direct substitution between SN74LS245DBRG4 and SN74LS245N or SN74LS245DWR in existing designs, provided package and thermal constraints are met.
SN74LS245DBRG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 20-SSOP (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, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SSOP
SN74LS245DBRG4 FAQ
1.How can I place an order for SN74LS245DBRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS245DBRG4 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 SN74LS245DBRG4 reliable?
The price and inventory of SN74LS245DBRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS245DBRG4 is usually 5 days.
3.What payment methods are accepted for SN74LS245DBRG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS245DBRG4 transactions.
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4.How is shipping managed for SN74LS245DBRG4?
SN74LS245DBRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS245DBRG4 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 SN74LS245DBRG4?
For technical support, including SN74LS245DBRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS245DBRG4 requirements.
6.How does Aetrix verify that SN74LS245DBRG4 is sourced from the original manufacturer or authorized distributors?
All SN74LS245DBRG4 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 SN74LS245DBRG4 meets industry standards.
7.What is the process for return or replacement of SN74LS245DBRG4?
All SN74LS245DBRG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS245DBRG4, 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 SN74LS245DBRG4 part is unused and in its original packaging.
Return procedure for SN74LS245DBRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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