Texas Instruments SN74CBT3245CDBR

Overview

SN74CBT3245CDBR from Texas Instruments is an 8-bit bidirectional FET bus switch with TTL-compatible control inputs, 3 Ω typical ON-state resistance, near-zero propagation delay (0.15 ns at 5 V), and −2 V undershoot protection on A/B ports. It enables low-distortion signal gating in USB interfaces and memory interleaving applications where level translation between 0.8 V–5 V logic domains is required.

For engineers reviewing the SN74CBT3245CDBR datasheet, SN74CBT3245CDBR pinout, SN74CBT3245CDBR application, or SN74CBT3245CDBR equivalent, key selection considerations include its Ioff partial-power-down capability, 5.5 pF OFF-state I/O capacitance, VCC operating range of 4 V to 5.5 V, and SSOP-20 package compatibility with legacy board layouts.

Technical Context

The SN74CBT3245CDBR implements eight independent analog/digital FET switches controlled by a single active-low OE input. When enabled, it provides bidirectional conduction with minimal voltage drop and no DC bias requirement-supporting true AC-coupled signal pass-through across mixed-voltage domains.

Its undershoot-protection circuitry actively clamps A/B port voltages down to −2 V during power sequencing or hot-plug events, while Ioff isolates ports when VCC = 0 V. The device meets JESD 78 Class II latch-up immunity (>100 mA) and JESD 22 ESD ratings (2000-V HBM, 1000-V CDM).

Key Specifications

Pinout & Package

SN74CBT3245CDBR uses the SSOP-20 (DB) package: 20-pin shrink small-outline package, 0.65 mm pitch, 7.4 mm × 5.3 mm body, 2.0 mm max height, with exposed thermal pad not present (unlike QFN). Pin 1 index located at top-left corner with beveled edge marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBTD3384CDBR and SN74LVC2G66DCUR, the SN74CBT3245CDBR delivers superior signal fidelity (lowest ron and Cio), integrated −2 V protection across all 16 I/Os, and guaranteed 8-bit coherency-making it optimal for high-integrity parallel bus isolation in industrial and computing applications.

Availability

SN74CBT3245CDBR is available at Aetrix Electronics and suitable for USB interface design, memory interleaving architectures, and bus isolation systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant SSOP packaging.

Supply support for SN74CBT3245CDBR 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 decades of expertise in high-speed interface solutions and industrial-grade reliability.

The SN74CBT3245CDBR belongs to TI's CBT (CrossBar Technology) bus switch family, engineered for zero-delay, low-distortion signal routing in mixed-voltage digital systems-particularly targeting computing, communications, and test equipment markets.

FAQ

What is the maximum signal frequency supported by the SN74CBT3245CDBR?

The SN74CBT3245CDBR does not specify a hard bandwidth limit but maintains signal integrity up to 100 MHz due to its 3 Ω ron and 5.5 pF Cio(OFF). Measured propagation delay is 0.15 ns at 5 V, confirming suitability for full-speed USB (12 Mbps) and fast parallel bus applications where edge fidelity matters more than absolute bandwidth.

Does the SN74CBT3245CDBR require external pull-up resistors on the OE pin?

Yes - to ensure high-impedance state during power-up or power-down, OE must be tied to VCC via a pull-up resistor. TI recommends minimum resistance based on driver sink capability; typical values range from 4.7 kΩ to 10 kΩ for standard CMOS drivers, ensuring reliable disable before VCC stabilizes.

Can the SN74CBT3245CDBR interface 1.8-V and 5-V logic domains simultaneously?

Yes - the SN74CBT3245CDBR supports 0–5.5 V signaling on both A and B ports regardless of VCC (4–5.5 V). This allows direct connection between 1.8-V FPGA I/O and 5-V microcontroller peripherals without level shifters, provided voltage limits on each side remain within specification.

Is the NC pin (Pin 20) on the SN74CBT3245CDBR electrically connected internally?

No - Pin 20 is explicitly designated "NC" (no internal connection) in the TI datasheet and package drawing DB0020A. It must remain unconnected on the PCB; routing traces or applying solder to this pin may cause mechanical stress or contamination but has no electrical effect on SN74CBT3245CDBR operation.

How does the Ioff feature protect systems during partial power-down?

The Ioff feature limits current to ≤10 µA when VCC = 0 V, preventing backflow from powered A/B ports into the unpowered VCC rail. This protects downstream regulators and avoids latch-up in adjacent ICs - a critical safeguard in modular systems like PCIe add-in cards or hot-swappable storage enclosures using SN74CBT3245CDBR for bus isolation.