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Texas Instruments SN74CBT3245DWR
- Part No.:
- SN74CBT3245DWR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- -
- Datasheet:
-
SN74CBT3245DWR.pdf
- Description:
- BUS DRIVER
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Inventory:1,000
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Product details
Overview
SN74CBT3245DWR from Texas Instruments is an octal bus switch IC with standard '245-type pinout, 5-Ω on-state resistance, TTL-compatible control inputs, and operation from –40°C to 85°C. It functions as a bidirectional 8-bit analog/digital signal path selector in memory expansion, data routing, and level-shifting applications.
For engineers reviewing the SN74CBT3245DWR datasheet, SN74CBT3245DWR pinout, SN74CBT3245DWR application, or SN74CBT3245DWR equivalent, key selection criteria include on-resistance (5–7 Ω), propagation delay (0.25 ns typ), high-impedance isolation during disable, and compatibility with 4–5.5 V supply rails in high-speed digital systems.
Technical Context
The SN74CBT3245DWR implements eight independent bilateral MOSFET switches controlled by a single active-low OE input. Its BiCMOS process enables low ron and fast switching while maintaining TTL-level logic thresholds (VIL ≤ 0.8 V, VVIH ≥ 2 V).
Each switch exhibits symmetrical conduction between A and B ports, with no inherent directionality. The device draws only 50 µA quiescent current at VCC = 5.5 V and supports 128 mA continuous channel current per switch under recommended operating conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4 V to 5.5 V - Ensures interoperability with 5-V TTL and mixed-voltage systems without level shifters. |
| ron (Typ) | 5 Ω - Minimizes voltage drop and signal distortion for analog/digital signals up to 128 mA per channel. |
| tpd (Typ) | 0.25 ns - Enables sub-nanosecond signal routing critical for high-speed bus arbitration and memory access timing. |
| ICC (Max) | 50 µA - Supports low-power standby states in battery-backed or energy-sensitive subsystems. |
| Cio(OFF) | 6 pF - Limits capacitive loading and crosstalk when switches are disabled, preserving signal integrity on shared buses. |
| Operating Temp | –40°C to 85°C - Qualified for industrial-grade environments including motor control, PLC I/O, and telecom line cards. |
Pinout & Package
SN74CBT3245DWR is housed in a 20-pin SOIC (DW) package with 0.300-inch body width and standard '245 pinout. Pin 1 is NC (no connect); pins 2–9 are A1–A8; pin 10 is GND; pin 11 is VCC; pin 12 is OE; pins 13–20 are B1–B8.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OE (Pin 12) | Active-low enable control | Drives all eight switches ON (A↔B connected) when low; places both ports in high-Z when high. |
| A1–A8 (Pins 2–9) | Input/Output port A | Bidirectional signal terminals-function identically as inputs or outputs depending on OE state and external drive. |
| B1–B8 (Pins 13–20) | Input/Output port B | Electrically identical to A-side; no internal directionality-supports true bidirectional signal flow. |
| VCC (Pin 11) | Power supply | Supplies BiCMOS switch core and control logic; requires local 0.1-µF bypass capacitor for noise suppression. |
| GND (Pin 10) | Ground reference | Common return path for all switch channels and control circuitry; must be low-impedance for stable ron. |
Key Features
| Feature | Design Value |
|---|---|
| 5-Ω typical on-state resistance | Enables minimal insertion loss and flat frequency response up to ~100 MHz for analog and digital signals. |
| Standard '245 pinout | Allows direct PCB footprint reuse with legacy 74-series transceivers and bus drivers, reducing layout redesign effort. |
| TTL-compatible control inputs | Accepts standard 5-V TTL logic levels without external biasing or level translation circuitry. |
| High-impedance OFF state | Provides >1012 Ω isolation between ports when disabled-prevents bus contention and back-driving in multiplexed systems. |
Applications
| Memory Expansion Interface | Data Bus Multiplexing |
|---|---|
Use Scenario: Expanding RAM capacity in microcontroller-based systems using shared address/data buses. IC Role / Device Role / Timing Role: Bidirectional signal gate that isolates auxiliary memory banks until selected, preventing bus conflicts during read/write cycles. Use Value: 0.25-ns propagation delay ensures timing compliance with 20+ MHz bus clocks; 5-Ω ron preserves signal rise/fall times across 8-bit parallel paths. | Use Scenario: Sharing a single 8-bit data bus among multiple peripherals (ADC, DAC, UART) in embedded instrumentation. IC Role / Device Role / Timing Role: Channel-selectable analog/digital signal router controlled by MCU GPIO, enabling time-division multiplexing without bus arbitration logic. Use Value: High-Z OFF state eliminates need for tri-state buffers on each peripheral; TTL-compatible OE simplifies direct MCU interface. |
| Level Translation Bridge | Hot-Swap Signal Isolation |
Use Scenario: Interfacing 3.3-V FPGA I/O to legacy 5-V peripheral logic where voltage translation is required. IC Role / Device Role / Timing Role: Passive bidirectional level shifter leveraging VCC-referenced switch threshold-no direction pin needed. Use Value: 4–5.5 V VCC range allows use with either side's supply; 6-pF Cio(OFF) minimizes capacitive coupling between domains. | Use Scenario: Protecting main system bus during hot insertion of daughterboards or field-replaceable modules. IC Role / Device Role / Timing Role: Signal isolation barrier activated only after power stabilization and firmware handshake via OE. Use Value: 128 mA per-channel rating supports robust transient current during plug-in; –40°C to 85°C rating ensures reliability in uncontrolled environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus switching applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74CBTD3384DWR | Includes integrated 5-V tolerant inputs and higher drive strength (200 mA), but requires 3.3-V VCC for optimal performance. | Better suited for mixed-voltage systems with 3.3-V core logic driving 5-V peripherals. | Select when higher current capability or 5-V tolerant inputs are required; not drop-in due to different VCC dependency. |
| QS3245M | Functionally equivalent per datasheet, same pinout and electrical specs, but manufactured by Fairchild (now ON Semiconductor) with distinct thermal derating curves. | Valid for second-source procurement where TI supply continuity is constrained. | Use as direct functional replacement where qualification allows alternate sourcing; verify thermal performance in target board layout. |
Compared with SN74CBT3245DWR, SN74CBTD3384DWR offers higher current handling but narrower VCC flexibility, while QS3245M provides identical functionality with vendor-specific thermal behavior-both require validation for thermal margin and long-term availability in production designs.
Availability
SN74CBT3245DWR is available at Aetrix Electronics and suitable for memory expansion interfaces, data bus multiplexing, level translation bridges, and hot-swap signal isolation requiring stable component supply and industrial temperature support.
Supply support for SN74CBT3245DWR 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 SN74CBT3245DWR belongs to TI's CBT (Crosspoint Bus Transceiver) logic family, designed specifically for high-speed, low-distortion signal routing in 5-V digital systems where minimal propagation delay and precise impedance matching are critical.
FAQ
What is the maximum continuous current per channel for the SN74CBT3245DWR?
The SN74CBT3245DWR supports up to 128 mA continuous channel current per switch under recommended operating conditions. This rating applies across the full temperature range (–40°C to 85°C) and is validated at VCC = 4.5 V to 5.5 V. Exceeding this current may increase ron, induce thermal stress, or degrade long-term reliability. For sustained 128 mA operation, ensure adequate PCB copper area and ambient airflow per TI's thermal guidelines for the DW package.
Does the SN74CBT3245DWR support bidirectional signal flow without external direction control?
Yes, the SN74CBT3245DWR supports fully bidirectional signal flow between ports A and B with no direction pin required. Each of the eight switches operates as a passive, symmetrical FET path-signal direction is determined solely by external drive sources on either side. This architecture eliminates timing skew between transmit/receive paths and simplifies interface design in applications like memory expansion and bus multiplexing where data flows both ways over the same lines.
What is the typical on-state resistance (ron) of the SN74CBT3245DWR and how does it vary with voltage?
The SN74CBT3245DWR has a typical on-state resistance of 5 Ω at VCC = 4.5 V, VI = 0 V, and II = 30 mA. At VI = 2.4 V and II = 15 mA, ron rises to 10–15 Ω. This voltage-dependent variation reflects the MOSFET channel characteristics-lower ron occurs near ground potential, increasing as the switched signal approaches VCC. Designers should account for this in precision analog routing or high-current digital paths.
Can the SN74CBT3245DWR be used with a 3.3-V supply voltage?
No, the SN74CBT3245DWR is not rated for 3.3-V operation. Its recommended VCC range is strictly 4 V to 5.5 V, and absolute maximum ratings specify –0.5 V to 7 V. Operating below 4 V risks incomplete turn-on of internal switches, increased ron, and unreliable OE control-TI does not characterize or guarantee performance outside the stated range. For 3.3-V systems, consider the SN74CBTD3384 or SN74LVC245 families instead.
How does the SN74CBT3245DWR handle input/output voltage beyond VCC or below GND?
The SN74CBT3245DWR permits input voltages from –0.5 V to 7 V, exceeding VCC or dropping below GND, provided clamp current limits (±50 mA) are observed. Internal diodes protect against overvoltage, but sustained violation of absolute maximum ratings may cause permanent damage. In practice, this tolerance supports hot-swap scenarios and mixed-voltage interfacing-however, operation must remain within the recommended 4–5.5 V VCC range for guaranteed switching performance and timing.
SN74CBT3245DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
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- Packaging:
- Bulk
- Product Status:
- Active
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- Independent Circuits:
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- Current - Output High, Low:
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- Voltage - Supply:
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SN74CBT3245DWR FAQ
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6.How does Aetrix verify that SN74CBT3245DWR is sourced from the original manufacturer or authorized distributors?
All SN74CBT3245DWR 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 SN74CBT3245DWR meets industry standards.
7.What is the process for return or replacement of SN74CBT3245DWR?
All SN74CBT3245DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT3245DWR, 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 SN74CBT3245DWR part is unused and in its original packaging.
Return procedure for SN74CBT3245DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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