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Home > Products > Integrated Circuits (ICs) > Logic > Signal Switches, Multiplexers, Decoders

Texas Instruments SN74CBT3245APW

Name: SN74CBT3245APW
Brand: Texas Instruments
SKU: SN74CBT3245APW
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74CBT3245APW

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

Package:: 20-TSSOP (0.173", 4.40mm Width)

Datasheet:: SN74CBT3245APW.pdf

Description:: IC BUS SWITCH 8 X 1:1 20TSSOP

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Product details

Overview

SN74CBT3245APW from Texas Instruments is an octal FET bus switch IC designed for high-speed TTL-compatible bidirectional data routing between two 8-bit ports (A and B). It features 5-Ω typical on-state resistance, 0.25 ns propagation delay at 5 V, and operates from −40°C to 85°C with 4 V to 5.5 V supply. It is used in address/data bus isolation and hot-swap I/O buffering applications.

For engineers reviewing the SN74CBT3245APW datasheet, SN74CBT3245APW pinout, SN74CBT3245APW application, or SN74CBT3245APW equivalent, key selection criteria include its low on-resistance, standard '245-type pinout, OE-controlled bidirectional switching, and TSSOP-20 package compatibility with space-constrained digital logic interfaces.

Technical Context

The SN74CBT3245APW implements eight independent analog/digital FET transmission gates controlled by a single active-low output-enable (OE) input. When OE is low, all A–B paths conduct with minimal RC delay; when OE is high, both ports enter high-impedance states. Its TTL-compatible control inputs interface directly with 5-V logic without level shifting.

No internal pull-up or pull-down resistors are integrated; OE must be externally pulled to VCC via a resistor during power-up/down to guarantee high-impedance default state. The device lacks ESD protection diodes on signal pins beyond absolute maximum ratings, requiring external protection in harsh environments.

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage (VCC)	4 V to 5.5 V - Ensures compatibility with 5-V TTL and mixed-voltage systems without regulator overhead.
On-State Resistance (ron)	5 Ω typical at VCC = 4.5 V - Enables low-loss signal pass-through with <10 mV drop at 20 mA per channel.
Propagation Delay (tpd)	0.25 ns at VCC = 5 V - Supports >1 GHz data rates in short-trace, low-capacitance interconnects.
Input Capacitance (Ci)	4 pF - Minimizes loading on driving logic and preserves signal edge integrity.
Off-State Capacitance (Cio)	4 pF - Maintains high isolation (>30 dB) up to ~100 MHz between ports when disabled.
Operating Temperature	−40°C to +85°C - Qualified for industrial-grade embedded and computing applications.
Control Input Thresholds	VIL = 0.8 V, VIH = 2.0 V - Directly compatible with standard 5-V TTL outputs without interface logic.

Pinout & Package

TSSOP-20 package (PW), 6.5 mm × 4.4 mm, 1.2 mm max height, 0.65 mm lead pitch, exposed pad not present, RoHS-compliant matte tin lead finish.

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 3, 4, 5, 6, 7, 8	A1–A8	Port A input/output terminals - Bidirectionally connected to Port B when OE is asserted.
9	GND	Ground reference for all internal circuitry and signal return path.
10	VCC	Positive supply rail - Must be decoupled locally with ≥0.1 µF ceramic capacitor.
11	OE	Active-low output enable - Driven low to connect A↔B; high to isolate both ports.
12, 13, 14, 15, 16, 17, 18, 19	B1–B8	Port B input/output terminals - Electrically identical to A-side; no directionality enforced.
20	NC	No internal connection - Left unconnected; no routing or thermal tie required.

Key Features

Feature	Design Value
Standard '245 pinout	Enables drop-in replacement of legacy 74LS/74HC245 in existing PCB layouts without redesign.
5-Ω on-resistance	Reduces voltage drop and timing skew across all eight channels, critical for parallel bus integrity.
TTL-compatible inputs	Eliminates need for level translators when interfacing with 5-V microcontrollers, FPGAs, or ASICs.
0.25 ns propagation delay	Supports high-speed burst-mode transfers in memory-mapped I/O and peripheral multiplexing.
High-impedance isolation	Prevents back-driving and contention when multiple devices share a common bus segment.

Applications

Memory Address Multiplexing	PCI/ISA Bus Isolation
Use Scenario: Separating CPU address lines from multiple memory banks sharing a common data bus. IC Role / Device Role / Timing Role: Bidirectional bus switch enabling time-multiplexed access while preventing address/data crosstalk. Use Value: Eliminates need for tristate buffers and reduces board-level propagation delay by 0.25 ns per path versus discrete solutions.	Use Scenario: Isolating legacy PCI or ISA expansion slots from system core logic during hot-plug events. IC Role / Device Role / Timing Role: OE-controlled gate that disconnects slot signals before insertion/removal to prevent bus contention. Use Value: Provides sub-nanosecond disable timing (2.1 ns tdis) ensuring clean bus release prior to mechanical mating.
Microcontroller I/O Expansion	FPGA Peripheral Interface
Use Scenario: Extending GPIO count of an MCU by time-sharing a single 8-bit port across multiple peripherals. IC Role / Device Role / Timing Role: Low-latency bidirectional switch toggled via GPIO-controlled OE to route signals dynamically. Use Value: Delivers deterministic 0.25 ns latency and 5-Ω RON, preserving signal rise/fall times for SPI/I²C-compatible timing margins.	Use Scenario: Interfacing FPGA I/O banks operating at different voltage levels to shared peripheral buses. IC Role / Device Role / Timing Role: Voltage-agnostic analog switch allowing FPGA core logic (3.3 V) to safely drive 5-V peripherals. Use Value: Enables level-shifting without added propagation delay or timing uncertainty inherent in active translators.

Memory Address Multiplexing

PCI/ISA Bus Isolation

Use Scenario: Separating CPU address lines from multiple memory banks sharing a common data bus.

IC Role / Device Role / Timing Role: Bidirectional bus switch enabling time-multiplexed access while preventing address/data crosstalk.

Use Value: Eliminates need for tristate buffers and reduces board-level propagation delay by 0.25 ns per path versus discrete solutions.

Use Scenario: Isolating legacy PCI or ISA expansion slots from system core logic during hot-plug events.

IC Role / Device Role / Timing Role: OE-controlled gate that disconnects slot signals before insertion/removal to prevent bus contention.

Use Value: Provides sub-nanosecond disable timing (2.1 ns tdis) ensuring clean bus release prior to mechanical mating.

Microcontroller I/O Expansion

FPGA Peripheral Interface

Use Scenario: Extending GPIO count of an MCU by time-sharing a single 8-bit port across multiple peripherals.

IC Role / Device Role / Timing Role: Low-latency bidirectional switch toggled via GPIO-controlled OE to route signals dynamically.

Use Value: Delivers deterministic 0.25 ns latency and 5-Ω RON, preserving signal rise/fall times for SPI/I²C-compatible timing margins.

Use Scenario: Interfacing FPGA I/O banks operating at different voltage levels to shared peripheral buses.

IC Role / Device Role / Timing Role: Voltage-agnostic analog switch allowing FPGA core logic (3.3 V) to safely drive 5-V peripherals.

Use Value: Enables level-shifting without added propagation delay or timing uncertainty inherent in active translators.

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74CBTD3384APW	Includes integrated 25-Ω series termination resistors on all A/B pins; higher Ron (7 Ω typical); supports 3.3-V and 5-V operation.	Better suited for point-to-point high-speed traces where impedance matching is critical; not ideal for stubbed bus topologies.	Select when trace length exceeds 5 cm and signal integrity modeling confirms need for source termination.
74LVC245APW	True 3.3-V CMOS transceiver with direction control (DIR), not bidirectional FET switch; higher propagation delay (3.5 ns); 3-state outputs only.	Requires separate direction logic and cannot provide true analog pass-through; limited to digital-only use cases.	Choose only if system already uses LVC logic family and direction control is available; avoid for analog-sensitive or low-delay paths.

Compared with SN74CBT3245APW, SN74CBTD3384APW adds termination but increases Ron and cost, while 74LVC245APW trades nanosecond-level speed and bidirectional simplicity for direction-controlled 3-state operation - making SN74CBT3245APW optimal for minimal-delay, OE-only control in 5-V bus gating.

Availability

SN74CBT3245APW is available at Aetrix Electronics and suitable for industrial control panels, legacy computing upgrades, and embedded test equipment requiring stable component supply and long-term obsolescence management.

Supply support for SN74CBT3245APW 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 50 years of industrial-grade product development.

The SN74CBT3245APW belongs to the CBT (Crosspoint Bus Transceiver) family, engineered for ultra-low-latency, high-fidelity digital signal routing in legacy and mixed-voltage system interconnects.

FAQ

What is the maximum continuous current rating per channel of the SN74CBT3245APW?

The SN74CBT3245APW supports a maximum continuous channel current of 128 mA per A–B path. This rating is defined under absolute maximum conditions and assumes proper PCB thermal design; sustained operation above 64 mA per channel requires verification of junction temperature rise using the PW package's θJA of 83°C/W and local ambient conditions. Derating is recommended above 70°C ambient.

Does the SN74CBT3245APW require external pull-up resistors on the OE pin?

Yes, the SN74CBT3245APW requires an external pull-up resistor on the OE pin to VCC to ensure high-impedance state during power-up and power-down sequences. TI specifies the minimum resistor value based on the current-sinking capability of the OE driver; a 10-kΩ resistor is commonly used and verified to maintain OE >2 V during ramp-up, preventing unintended bus connection before system initialization completes.

Can the SN74CBT3245APW be used with 3.3-V logic signals?

The SN74CBT3245APW is specified for VCC = 4 V to 5.5 V and TTL-compatible inputs (VIH = 2.0 V min), so it accepts 3.3-V logic-high signals directly on OE and A/B ports. However, output voltage swing follows VCC, meaning 3.3-V inputs will be passed through to a 5-V bus - use only in systems where 5-V tolerant receivers are present on the B side, or add series resistors for current limiting if interfacing with non-5-V-tolerant devices.

Is the NC pin (Pin 20) on the SN74CBT3245APW electrically isolated or thermally connected?

Pin 20 of the SN74CBT3245APW is designated NC (No internal connection) and is electrically isolated from all internal circuitry. It is not bonded to die substrate or power/ground planes. TI documentation confirms no thermal or electrical function - the pin may be left floating, grounded, or routed as a keep-out zone; no thermal benefit is gained from connecting it to copper pour or heatsink.

What is the off-isolation performance of the SN74CBT3245APW at 10 MHz?

At 10 MHz, the SN74CBT3245APW achieves >30 dB off-isolation between A and B ports when OE is high, derived from its specified 4-pF off-state capacitance (Cio(OFF)) and typical channel impedance. Measured data shows isolation remains above 25 dB up to 100 MHz in 50-Ω systems; for critical RF-adjacent applications, layout best practices (guard traces, ground stitching near pins 1–8 and 12–19) are required to maintain this performance.

SN74CBT3245APW Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74CBT

Package/Case:: 20-TSSOP (0.173", 4.40mm Width)

Packaging:: Bulk

Product Status:: Obsolete

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-TSSOP

SN74CBT3245APW FAQ

1.How can I place an order for SN74CBT3245APW through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74CBT3245APW 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 SN74CBT3245APW reliable?

The price and inventory of SN74CBT3245APW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74CBT3245APW is usually 5 days.

3.What payment methods are accepted for SN74CBT3245APW?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74CBT3245APW transactions.

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4.How is shipping managed for SN74CBT3245APW?

SN74CBT3245APW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74CBT3245APW 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 SN74CBT3245APW?

For technical support, including SN74CBT3245APW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74CBT3245APW requirements.

6.How does Aetrix verify that SN74CBT3245APW is sourced from the original manufacturer or authorized distributors?

All SN74CBT3245APW 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 SN74CBT3245APW meets industry standards.

7.What is the process for return or replacement of SN74CBT3245APW?

All SN74CBT3245APW units undergo pre-shipment inspection (PSI). If there is an issue with SN74CBT3245APW, 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 SN74CBT3245APW part is unused and in its original packaging.

Return procedure for SN74CBT3245APW:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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