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Texas Instruments SN74CBT3245ADBR
- Part No.:
- SN74CBT3245ADBR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 20-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
SN74CBT3245ADBR.pdf
- Description:
- IC BUS SWITCH 8 X 1:1 20SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,589
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Product details
Overview
SN74CBT3245ADBR from Texas Instruments is an octal FET bus switch IC designed for high-speed TTL-compatible bidirectional signal routing between two 8-bit ports (A and B). It features 5-Ω on-state resistance, 0.25 ns typical propagation delay at 5 V, and operates from −40°C to 85°C. It is used in data path isolation, level translation, and hot-swap interface circuits.
For engineers reviewing the SN74CBT3245ADBR datasheet, SN74CBT3245ADBR pinout, SN74CBT3245ADBR application, or SN74CBT3245ADBR equivalent, key selection criteria include on-resistance matching, OE-controlled bidirectional switching, SSOP-20 thermal performance (θJA = 70°C/W), and compatibility with 4–5.5 V supply rails.
Technical Context
The SN74CBT3245ADBR implements eight independent analog switches using NMOS FETs, enabling low-distortion, bidirectional signal flow between A and B ports. Its TTL-compatible control input (OE) directly interfaces with standard logic families without pull-up resistors under normal operation.
Switching is controlled solely by the OE pin: low enables connection (A↔B), high places both ports in high-impedance isolation. The device lacks internal ESD protection diodes on signal paths, requiring external clamping in overvoltage-prone environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| On-state resistance (ron) | 5 Ω typical at VCC = 4.5 V - ensures minimal voltage drop and signal attenuation across switched paths |
| Propagation delay (tpd) | 0.25 ns typical at VCC = 5 V - supports >1 GHz data rates in short-trace applications |
| Supply voltage range | 4 V to 5.5 V - compatible with 5-V TTL and mixed-voltage system backplanes |
| Input voltage range (VI) | −0.5 V to 7 V - allows safe operation with input overshoot up to 7 V before clamp activation |
| Continuous channel current | 128 mA per switch - supports driving 50-pF loads at full speed without derating |
| Thermal resistance (θJA) | 70°C/W for SSOP-20 package - defines maximum power dissipation (≈171 mW at ΔT = 12°C rise) |
| Operating temperature | −40°C to +85°C - qualified for industrial-grade embedded and communications equipment |
Pinout & Package
SN74CBT3245ADBR is housed in a 20-pin SSOP (Shrink Small Outline Package) with 0.65 mm pitch, 7.4 mm × 5.3 mm body, and 2.0 mm max height per JEDEC MO-150. Pin 1 index is located at top-left corner with notch marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A1–A8 | Port A input/output terminals - bidirectionally connected to B1–B8 when OE is low |
| 9 | GND | Ground reference for all internal circuitry and signal return path |
| 10 | VCC | Positive supply rail (4–5.5 V) powering internal switch bias and control logic |
| 11 | OE | Active-low output-enable control - drives switch state; must be pulled high during power-up for safe default isolation |
| 12, 13, 14, 15, 16, 17, 18, 19 | B1–B8 | Port B input/output terminals - mirror A-port functionality in bidirectional mode |
| 20 | NC | No internal connection - left unconnected; no electrical function or thermal role |
Key Features
| Feature | Design Value |
|---|---|
| Standard '245-type pinout | Enables drop-in replacement of legacy 74LS245/74ACT245 in existing PCB layouts without redesign |
| TTL-compatible input levels | Accepts VIH ≥ 2 V and VIL ≤ 0.8 V - eliminates need for level-shifting drivers in 5-V systems |
| Low on-state resistance | 5 Ω typical - reduces insertion loss and maintains signal integrity for high-frequency digital buses |
| High-speed switching | 0.25 ns tpd at 5 V - supports clean edge transmission in DDR, PCI, and parallel address/data paths |
| Power-up/down high-Z safety | OE tied to VCC via pull-up ensures automatic isolation during supply ramp - prevents bus contention |
Applications
| PCI Bus Isolation | Memory Address Multiplexing |
|---|---|
Use Scenario: Isolating PCI add-in card data lines from motherboard during hot-plug insertion or removal. IC Role / Device Role / Timing Role: Bidirectional bus switch controlled by slot reset signal to prevent data corruption during card insertion. Use Value: 5-Ω ron and sub-nanosecond tpd preserve PCI timing margins while eliminating cross-talk between active and inactive slots. | Use Scenario: Sharing a single address bus between multiple memory banks in microcontroller-based data loggers. IC Role / Device Role / Timing Role: OE-gated octal switch enabling time-multiplexed access to SRAM and Flash address lines. Use Value: TTL-compatible inputs simplify control from MCU GPIO; low ron avoids address skew across 8-bit lanes. |
| Hot-Swap Backplane Interface | Legacy Parallel Port Expansion |
Use Scenario: Enabling safe insertion/removal of daughter cards in telecom shelf backplanes with live 5-V power rails. IC Role / Device Role / Timing Role: Signal path isolator placed between backplane connector and local FPGA I/O, controlled by presence detect signal. Use Value: High-impedance default state (OE = high) prevents bus loading during card insertion; 128 mA per switch handles full drive strength. | Use Scenario: Extending parallel printer port signals to external test instrumentation in lab automation systems. IC Role / Device Role / Timing Role: Bidirectional buffer between PC LPT port and custom peripheral, supporting both status readback and command write. Use Value: Standard '245 pinout allows reuse of existing ribbon cable assemblies; 0.25 ns tpd preserves handshake timing integrity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus switch applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74CBTD3384ADBR | Includes integrated 25-Ω series termination resistors on all A/B pins - adds 2.5 Ω per path vs. SN74CBT3245ADBR's 5 Ω ron | Designed for impedance-matched trace routing; requires no external termination components | Select when driving long (>10 cm) PCB traces or cables where signal integrity demands controlled impedance |
| SN74LVC245APWR | CMOS-based 8-bit transceiver with direction control (DIR) and 3-state outputs - not bidirectional analog switch; ron not specified | Provides true directionality and level shifting (1.65–5.5 V); unsuitable for analog or passive signal routing | Select when bidirectional analog pass-through is unnecessary and discrete direction control or wider VCC range is required |
Compared with SN74CBT3245ADBR, SN74CBTD3384ADBR adds built-in termination at the cost of higher on-resistance, while SN74LVC245APWR replaces analog switching with digital transceiver logic - making it incompatible for passive signal routing but more flexible for level-shifted directional data transfer.
Availability
SN74CBT3245ADBR is available at Aetrix Electronics and suitable for PCI bus isolation, memory address multiplexing, and hot-swap backplane interface applications requiring stable component supply and industrial-temperature operation.
Supply support for SN74CBT3245ADBR 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 connectivity technologies with over 90 years of innovation in industrial, automotive, and communications markets.
The SN74CBT3245ADBR belongs to TI's CBT (Crosspoint Bus Transceiver) family, engineered for ultra-low-latency, low-resistance signal routing in high-speed digital backplanes and modular system architectures.
FAQ
What is the maximum continuous current rating per channel for SN74CBT3245ADBR?
The SN74CBT3245ADBR supports a continuous channel current of 128 mA per switch. This rating applies under recommended operating conditions (VCC = 4–5.5 V, TA = −40°C to 85°C) and ensures reliable conduction without thermal runaway or contact degradation. Exceeding this value risks permanent damage to the internal FET structure. The SN74CBT3245ADBR datasheet specifies this limit in the Absolute Maximum Ratings table.
Does SN74CBT3245ADBR require external pull-up resistors on the OE pin?
Yes - to ensure high-impedance isolation during power-up or power-down, OE must be tied to VCC through an external pull-up resistor. The minimum resistance value depends on the driver's current-sinking capability; TI recommends verifying against the specific control source's IOL. This requirement is explicitly stated in the SN74CBT3245ADBR datasheet's "description/ordering information" section.
Can SN74CBT3245ADBR operate with a 3.3-V supply?
No - the SN74CBT3245ADBR has a minimum recommended VCC of 4 V and absolute minimum of −0.5 V. At 3.3 V, the internal FETs fail to fully enhance, resulting in elevated on-state resistance (>15 Ω), increased propagation delay, and potential signal integrity failure. The SN74CBT3245ADBR datasheet confirms 4 V as the lower bound of recommended operating conditions.
Is SN74CBT3245ADBR pin-compatible with older 74-series bus switches like 74LS245?
Yes - the SN74CBT3245ADBR uses a standard '245-type pinout across DB, DW, PW, and RGY packages, enabling direct PCB footprint compatibility with 74LS245, 74ACT245, and other industry-standard octal transceivers. However, unlike those TTL/CMOS devices, the SN74CBT3245ADBR functions as a passive analog switch rather than an active transceiver with direction control.
What is the thermal resistance (θJA) of SN74CBT3245ADBR in its SSOP package?
The SN74CBT3245ADBR in the SSOP-20 (DB) package has a junction-to-ambient thermal resistance (θJA) of 70°C/W, as specified in the Absolute Maximum Ratings table. This value assumes standard JEDEC test board conditions (2S2P) and determines allowable power dissipation: for a 12°C ambient-to-junction rise, maximum continuous power is ~171 mW. The SN74CBT3245ADBR datasheet lists this parameter under thermal characteristics.
SN74CBT3245ADBR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74CBT
- Package/Case:
- 20-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Bus Switch
- Circuit:
- 8 x 1:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- -
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SSOP
SN74CBT3245ADBR FAQ
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For technical support, including SN74CBT3245ADBR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74CBT3245ADBR requirements.
6.How does Aetrix verify that SN74CBT3245ADBR is sourced from the original manufacturer or authorized distributors?
All SN74CBT3245ADBR 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 SN74CBT3245ADBR meets industry standards.
7.What is the process for return or replacement of SN74CBT3245ADBR?
All SN74CBT3245ADBR units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT3245ADBR, 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 SN74CBT3245ADBR part is unused and in its original packaging.
Return procedure for SN74CBT3245ADBR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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